Book - The microscopic anatomy of the human body, in health and disease

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Hassall AH. The microscopic anatomy of the human body, in health and disease. (1849) Samuel Hurley, Fleet Street, London.

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This historic 1849 textbook by Hassall describes development and histological structure of the human body. Note that this is an 1840's textbook with many functional descriptive inaccuracies.


Hassall's corpuscles
This historic textbook is often cited as the original text source for identification of "Hassall's corpuscles" within the thymus. Plate LX1-7 Follicles of thymus, with vessels, 33 diam




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The text on this current page is from the later American edition.
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Contents

The Microscopic Anatomy of the Human body, in Health and Disease

The Human Body, in Health and Disease

Arthur Hill Hassall
Arthur Hill Hassall

Illustrated With Numerous Drawings In Colour.

By

Arthur Hill Hassall, M,B.

Author Of A “History Of The British Freshwater Algie

Fellow Of The Linniean Society ;

Member Of The Royal College Of Surgeons Of England ; One Of The Council Of Tile London Botanical Society ; Corresponding Member Of The Dublin Natural History Society.


In Two Volumes.

VOL. I

LONDON: SAMUEL HIGH LEY, 32. FLEET STREET.

1849.

To Thomas War Lea, Esq., M.P., Coroner, Etc. Etc.


Dear Sir,

To you I dedicate the accompanying pages, devoted to the elucidation of a department of minute anatomy of daily increasing interest and importance.

I thus dedicate this work to you on two grounds ; the one personal and private, the other public.

On rny mentioning the design of this work to you — and you were one of the first persons to whom it was mentioned — you were kind enough to express yourself in terms of approval and encouragement, and to profFer any assistance in your power in the furtherance of my undertaking. Of this conduct on your part I have ever entertained a pleasing and grateful remembrance ; and it is this which constitutes the private ground of my dedication.

But I dedicate this work to you on a higher and more important ground. I have for many years seen in you the able and strenuous advocate — amidst much obloquy and misrepresentation — of the rights of that profession of which we are both members : on this high ground I conceive you to be entitled to the gratitude of your professional brethren ; and with this feeling on my mind of your conduct and services in a good cause,


I beg to subscribe myself,

Yours, very faithfully,

THE AUTHOR,


Preface 1851

Dear Sir:

To you I dedicate the accompanying pages, devoted to the elucidation of a department of minute anatomy of daily increasing interest and importance.

I thus dedicate this work to you on two grounds; the one personal and private, the other public.

On my mentioning the design of this work to you — and you were one of the first persons to whom it was mentioned — you were kind enough to express yourself in terms of approval and encouragement, and to proffer any assistance in your power in the furtherance of my undertaking. Of this conduct on your part I have ever entertained a pleasing and grateful remembrance; and it is this which constitutes the private ground of my dedication.

But I dedicate this work to you on a higher and more important ground. I have for many years seen in you the able and strenuous advocate — amidst much obloquy and misrepresentation — of the rights of that profession of which we are both members: on this high ground I conceive you to be entitled to the gratitude of your professional brethren; and with this feeling on my mind of your conduct and services in a good cause,

I beg to subscribe myself,

Yours, very faithfully,

THE AUTHOR.


Preface English Edition 1846

After three years of more or less constant labour, the welcome and often-wishedfor period of the completion of this work has arrived, and the author is at liberty to address himself to his readers, and to explain the motives and the circumstances which have led to its production.

The idea of this work presented itself to the author's mind several years since ; it was not, however, until about the period above referred to, that its actual execution was commenced.

At the time when its design was first conceived, the powers of the microscope in developing organic structure were but beginning to be known and appreciated, and the importance of its application to physiology and pathology was but dimly perceived.

At that period, also, but few complete works devoted to microscopic anatomy had appeared in any language, native or foreign; more recently this deficiency, as respects France and Germany, has been well supplied by the appearance of several original works, as those of Donne, Mandl, Lebert, Miiller, Henle, Vogel, Gerber, and Wagner; England, however, has not as yet contributed her share of distinct and independent works on general anatomy : not that our observers have been idle, or have neglected a field of inquiry so interesting and important, resting satisfied with mere translations: a whole host of intelligent and able microscopists have applied themselves to the investigation of the ultimate structure of the several tissues and organs, and this with a preeminent degree of success. Among the more remarkable of these investigators, the following may be enumerated: Gulliver, Martin Barry, Busk, Addison, Kiernan, Sharpey, Goodsir, Tomes, Toynbee, Johnson, Simon, Todd and Bowman, Quekett, Erasmus Wilson, Hughes Bennet, Carpenter, Rainey, Handheld Jones, and Gairdner.

The results of the labours of these observers have. not as yet, however, been embodied in a separate work ; but some of them have been mixed up with works on descriptive anatomy and physiology, as in Sharpey's edition of Quain's Anatomy, in Carpenter's " Principles " and " Manual " of Physiology, and in Todd and Bowman's " Physiological Anatomy." The last is an admirable book, full of original research and important facts.

Now, one of the purposes, the accomplishment of which has been attempted in the following pages, has been the collecting together of the numerous communications on general anatomy to be found scattered through the pages of our different scientific periodicals, and their combination into a whole.

The further objects which the author has had in view in the production of this work have been simplicity of description, fidelity of representation, and the addition of such facts and particulars as have occurred to himself in the course of his own investigations; and he may take this opportunity of observing, that in but few instances has he written upon a subject without previous investigation.


The author considers it right, in justice to himself, that certain disadvantages under which the work has been produced should be mentioned : these were, constant engagement in general practice, much anxiety, and, though last, not least, ill health. These would have been sufficient to have deterred many from the undertaking altogether. Although this has not been the effect upon the author, yet it cannot be questioned but that they have operated in some respects to the disadvantage of the work ; and he begs that it may be taken neither as the measure of that of which the subject is capable, nor of the author's powers of observation and description exercised under more favourable circumstances of health, leisure, and feeling.

The author makes these few remarks not in order to deprecate any fair criticism, but simply that the truth in reference to the production of this work may be known in justice both to the writer and the reader.

Having said thus much in relation to the work itself, the author has now the pleasing task of returning his acknowledgments to those who have in any way assisted him in his laborious though most agreeable task; these are particularly due to the following: Mr. Quekett, Dr. Handfield Jones, Professor Sharpey, Mr. Tomes, Mr. Bowman, Mr. Busk, Professor Owen, Mr. Canton, Dr. Carpenter, Dr. Letheby, Dr. Robert Barnes, Mr. Ransom, Mr. Pollock, and Mr. Gray, of St. George's Hospital, Mr. Hett, and Mr. Andrew Ross: they are also due to Mr. Drewry Ottley; Dr. Radcliffe Hall; Mr. Coppin, of Lincoln's Inn; Messrs. Welch and Jones, of Dalston; Mr. Berry, of James-street, Covent Garden ; Mr. Cowdry, of Great Torrington ; Dr. Jones, of Brighton; Dr. Chambers, of Colchester; Mr. Milner, of Wakefield; Mr. Walker, of St. John's-street Road; Mr. Ringrose, of Potter's Bar; Dr. Halpin, of Cavan ; and Mr. H. Hailey, of Birmingham.

To Dr. Letheby I hope shortly to have a second opportunity of rendering my thanks, in connexion, viz: with the work on crystals, entitled "Human Crystallography," an announcement of which appeared some months since, and towards the completion of which considerable materials have already been collected.

To Mr. Hett, my thanks are especially due for having, at considerable trouble and inconvenience, furnished me with very many of the injections required to illustrate Part XV. of the "Microscopic Anatomy;" these, together with numerous other injected preparations of that gentleman which I have seen, have been of first-rate quality; and the microscopic anatomist has reason to hail the advent of such a man to the cause of general anatomy with the highest satisfaction.

To Mr. Andrew Ross, on this, as on a former occasion, I have to express my obligations, Mr. R. having at all times furnished me with any information I might require, as well as provided me with any necessary apparatus.

Thus much for friends. If, in the inditing of this work, I have made a single enemy, I am sorry for it, and still more so if I have given any real occasion for offence. If, in differing from other observers as to certain facts and conclusions, I have expressed myself in such a manner as to wound their feelings, as in one or two instances I fear I may have done, I much regret it: the differences among men whose common aim is the knowledge of truth, as manifested in the works of creation, should never be deep or lasting; for this community of purpose should ever be a firm bond of union between such men, seekers after truth, and should displace from their minds the lesser and grosser feelings of rivalry and ill-will.

Notting Hill, July 27th, 1849,

Preface by the American Editor

The Microscopic Anatomy of Dr. A. H. Hassall is offered to the student in this department of Medical Science, as the only completed work on the subject in the English language.

In the present edition, the introduction and additions to the text, are chiefly of a practical nature; this feature, it is hoped, will not detract from the high scientific character of the original work, but will give it some additional value for those who wish to pursue the study of minute anatomy, by the aid of the microscope.

It will be observed that, in some instances, Dr. Hassall's views differ from those of other writers. Some of these views Dr. Hassall has himself modified, and made mention of the fact in the Appendix : other instances of difference have been pointed out by the editor; others, again, and these are chiefly matters of opinion on disputed points, have not been alluded to, as it did not seem desirable to extend the work, by adducing farther conflicting statements on unsettled questions.

The ten Plates added to the American edition, are mostly original, and from the human subject. The drawings for these Plates were made by aid of one of Mr. Spencer's excellent microscopes, which was obligingly loaned for the purpose by Prof. C. R. Gilman.

For some of the specimens illustrating certain points of anatomy which have been figured, the editor is indebted to Mr. Hett, of London, so well known to microscopists for his beautiful preparations of healthy and diseased structures. For other objects of value, to Drs. Neill and Goddard of Philadelphia, whose minute injections have equalled the best foreign ones.

Almost all the drawings were made by Mr. W. R. Lawrence of Hartford, whose previous experience in drawing from the microscope, contributed greatly to the accurate representations he has given. Several of the figures in Plates LXXIV. and LXXV., were drawn by Mr. H. A. Daniels, who is well known to the profession of this city as an accomplished anatomical draughtsman.

To all these gentlemen, as well as to Prof. A. Clark, and A. S. Johnson, Esq., of New-York, for valuable hints in manipulation; and, lastly, to the publishers, for the generous manner in which they allowed the expensive additions, and for the excellent style in which they have issued the work, the editor desires to tender his acknowledgments.

The additions to the text are inserted at the end of the Articles, and enclosed in brackets.

New-York, 112 West Twenty-Second Street, May 1st, 1851.

Contents

Introduction

Its Object 27

Choice of a Microscope 27

Division of Subject 27

I. — Microscopes And Their Accessories.

Ross' Microscope 29

Powell and Lealand's ditto 29

Smith and Beck's ditto 30

Chevalier's ditto 30

Oberhauser's ditto 30

Brunner's ditto

Nachet's ditto 31

Spencer's ditto 31

Allen's ditto 33

Pike and Sons' ditto 33

Accessory Instruments 33

II. — PREPARATION OF OBJECTS.

Of Fluids . . 37

Of Solids . 38

Fine Injections 42

Materials, used in 42

General Directions 42

Injections with Turpentine . . 42

Ditto with Ether 43

Ditto by Double Decomposition 44

Ditto with other Materials 48

III. — PRESERVATION OF OBJECTS.

Different Cements used 49

Glass Slides and Cells 51

Thin Glass . 51

Thin-glass Cells 54

Drilled ditto 54

Tube ditto 54

Built-up ditto 55

Gutta-percha ditto 55

FLUIDS FOR MOUNTING OBJECTS.

Alcohol and Water 56

Goadby's Solutions 56

Other Fluids . ... . . 57

METHODS OF MOUNTING OBJECTS.

The dry way

In Canada Balsam with heat

In Fluid

As Opaque Objects

Labelling Slides

Cabinets


PART I. FLUIDS OF THE HUMAN BODY.

ARTICLE I.

The Lymph and Chyle. — General description of Lymphatics and Lacteals, page 67. Characters and Structure of Lymph, 68. Ditto of Chyle, 68. Ditto of Fluid of Thoracic duct, 70. Corpuscles of Thymus, 72. Structure of Lymphatics, 76. Examination of Lymph and Chyle, 78.

ARTICLE II.

The Blood. — Definition, 80. Coagulation of the Blood, without the Body, 80. Formation of the Clot, 81. Formation of the Buffy Coat of the Blood, 83. Cupping of the Clot, 85. Coagulation of the Blood in the Vessels after Death, 86. Signs of Death, 86. Globules of the Blood, 88. The Red Globules, 89. The White Globules, 100. Molecules of the Blood, 121. Blood Globules of Reptiles, Fishes, and Birds, 123. Capillary Circulation, 125. Circulation in the Embryo of the Chick, 129. Venous and Arterial Blood, 134. Modifications of the Blood Corpuscles the results of different external Agencies, 138. Modifications, the results of Decomposition occurring in Blood abandoned to itself without the Body, 139. Modifications, the results of Decomposition occurring in Blood within the Body after Death, 139. Causes of Inflammation, 140. Pathology of the Blood, 142. Importance of a Microscopic Examination of the Blood in Criminal Cases, 164. Examination of, 169. Preservation of, 170.

ARTICLE ill.

Mucus, 171. General characters, 171. Mucous Corpuscles, 174. Nature of Mucous Corpuscles, 176. The Mucus of different Organs, 179.

ARTICLE IV.

Pus, 183. General characters, 183. Identity of the Pus and Mucous Corpuscle, 183. Distinctive characters of Mucus and Pus, 186. Distinctions between certain forms of Mucus and Pus, 190. Detection of Pus in the Blood, 191. False Pus, 192. Metastatic Abscesses, 193. Venereal Vibrios, 194.

ARTICLE V.

Milk, 195. Serum of the' Milk, 196. The Globules, 197. Colostrum, 201. Pathological Alterations of the Milk, 203. The Milk of Unmarried Women, 206. The Milk of Women previous to Confinement, 206. The Milk of Women who have been delivered, but who have not nursed their Offspring, 208. Milk in the Breasts of Children, 208. Different kinds of Milk, 208. Good Milk, 210. Poor Milk, 212. Rich Milk, 213. Adulterations of Milk, 213. Formation of Butter, 214. Modifications of Milk abandoned to itself, and in which Putrefaction has commenced, 215. The Occurrence of Medicines, &c. in the Milk, 217. Examination of Mucus, Pus, and Milk, 217.

ARTICLE VI.

The Semen, 218. Spermatozoa, Form, Size and Structure of, 218. Motions of the Spermatozoa, 225. Spermatophori, 228. Development of the Spermatozoa, 229. The Spermatozoa essential to Fertility, 232. Pathology of the Seminal Fluid, 234. Application of a Microscopic examination of the Semen to Legal Medicine, 237. Examination of Semen, 239.

ARTICLE VII.

Saliva, Bile, Sweat, Urine, 240. The Saliva, 241. The Bile, 242. The Sweat, 243. The Urine, 245. Pathology of the Urine, 246. Examination of Urine, 252.

PART II. SOLIDS OF THE HUMAN BODY. ARTICLE VIII.

Fat, 254. Form, Size, and Structure of the Fat Corpuscle, 254. Distribution of Fat, 259. Disappearance of, 261. Injection of Fat-vesicles, 263.

ARTICLE IX.

Epithelium, Distribution of, 264. Tesselated Epithelium, Structure of, 265. Conoidal Epithelium, naked and ciliated, Structure of, 267. Development and Multiplication of Epithelium, 271. Nutrition of Epithelium, 272. Destruction and Renewal of Epithelium, 272. Epithelial Tumours, 275. Examination of Epithelium, 275.

ARTICLE X.

Epidermis, Distribution, Form, Structure, and Development of, 277. Epidermis of the White and Coloured Races, 279. Destruction and Renewal of Epidermis, 279. Description of, according to Mr. Rainey, 281. Examination of, 281.

article xi. The Nails, Structure of, 282. Development of, 283. Examination of, 258.

article xii. Pigment Cells, Structure and Varieties of, 286. Study of, 290.

article XI II.

Hair, Form of, 291. Size of, 292. Structure of, 292. Growth of, 297. Regeneration of, 297. Nutrition of, 299. Distribution of, 300. Colour of, 301. Properties of, 302. The Hair of different Animals, 303. Method of making thin sections of, 305.

article XIV.

Cartilages, 306. True Cartilages, 306. Fibro-Cartilages, 309. Nutrition of Cartilage, 311. Growth and Development of Cartilage, 312. Study of Cartilage, 316.

article XV.

Bone, Structure of, 317. Growth and Development of, 324. Accidental Ossification, 332. Preparation of Bone, 334.

ARTICLE XVI.

Teeth, Structure of, 335. Development of, 339. Caries of, 344. Tartar on, 345. Method of making sections of, 345.


ARTICLE XVII.

Cellular or Fibrous Tissue, 346. Inelastic or White Fibrous Tissue, 346. Elastic or Yellow Fibrous Tissue 348 Development of Fibrous Tissue, 352.

ARTICLE XVIII.

Muscle, 354. Structure of Muscle, 355. Structure of the Unstriped Muscular Fibrilla, 355. Structure of the- Striped Muscular Fibre, 357. Union of Muscle, with Tendon, 362. Muscular Contraction, 363. Development of Muscle, 367. Prof. Kolliker on Unstriped Muscle, 371. Mode of preparing for examination, 375.

article XIX.

Nerves, 376. Structure of, 376. Cerebro- Spinal System. Secreting or Cellular Structure of, 376. Tubular Structure of, 378. Sympathetic System, 380. GelatinNerve, Fibres of, 380. Structure of Ganglia, 383. Origin and Termination of Nerves, 384. Pacinian Bodies, 386. Development and Regeneration of Nervous Tissue, 388. Researches of M. Robin, 391. Preparation of, for examination, 394.


ARTICLE XX.

Organs of Respiration, 395. Aeriferous Apparatus. Bronchial Tubes, and AirCells, 395. Vascular Apparatus, 398. Pathology, 399. Mr. Rainey's views on, 404. Examination of, 405.

ARTICLE XXI.

Glands, 406. Classification of Glands, 408. a. Follicles, 410. Stomach Tubes, 412. Fallopian and Uterine Tubes, 413. Solitary Glands, 413. Aggregated Glands, 414. B. Sebaceous Glands, 414; comprising the Meibomian Glands, 416. Glands of Hair Follicles, 416. The Caruncula Lachrymalis, 418. Glands of Nipple, 418, and Glands of Prepuce, 418. Mucous Glands, 418; including the Labial, Buccal, Lingual, Tonsilitic, Tracheal, and Bronchial Glands; also, the Glands of the Uvula, Brunner's and Cowper's Glands, 418. Brunner's Glands, 421. Coivper's Glands, 421. c. Salivary Glands, 422. Lachrymal Glands, 423. Mammary Glands, 423. Liver, Structure of, 423. Pathology of, 432. Examination of, 435. Prostate Gland, 436. d. Sudoriparous Glands, 437. Structure and examination of, 439. Axillary Glands, 441. New Tubular Gland in Axilla, Plate LVIL, fig. 4 b. Ceruminous Glands, 441. Kidneys, 442. Secreting Apparatus of, including Tubes, Malpighian Bodies, and Epithelial Cells, 442. Vascular Apparatus of, 444. Development of the Kidney, 449. Pathology of, 453. Examination of, 482. Testis, 483. E. Thymus Gland, 484. Thyroid Gland, 486 Supra-renal Capsules, 488. Spleen, 489. i\ Absorbent Glands, 492. Villi of the Intestines, 493. Examination of, 496.

ARTICLE XXII.

Organs of the Senses, 497. Touch: .Papillary Structure of the Skin, 497. Examination of, 500. Taste : Papillary Structure of the Mucous Membrane of the Tongue, 501. Smell: Structure of the Mucous Membrane of the Nose, 505. Vision: Structure of the Globe of the Eye, 509. Sclerotic, 509. Cornea, 510. Choroid, 514. Retina, 518. Vitreous Body, 521. Crystalline Lens, 522. Dissection of the Eye, 533. Hearing: Organ of, 523 External Ear, 523. Middle Ear, 523. Internal Ear, 525.

APPENDIX.

Pituitary Gland, 535. Pineal Gland, 536. Pia Mater, 537. Pacchionian Glands, 538. Development of the Fat Vesicle, 538. On the Structure and Formation of the Nails, 541. On the Ganglionic Character of the Arachnoid Membrane, 543. Structure of the Striped Muscular Fibrilla, 547. Structure of the Bulb of the Hair, 547. Synovial Fringes, 547. Structure of the Sudoriparous Glands, 547.

Index of the Illustrations

The whole of the following illustrations ake original with but nine exceptions:

BLOOD.

Corpuscles of man, the red with the centres clear, 670 diam

The same, the red with the centres dark, 670 diam.

The same, seen in water, 670 diam. .

The same, the red united into rolls, 670 diam.

Tuberculated condition of the red corpuscles, 670 diam

White corpuscles of man, in water, 670 diam.

Corpuscles of frog, 670 d'iam. ....

The same, with the nucleus of the red visible, 670 diam.

The same, in water, 670 diam.

The same, after prolonged action of water, 670 diam

Nuclei of red corpuscles of frog, 670 diam.

Elongation of red corpuscles of ditto, 670 diam.

Corpuscles of the dromedary, 670 diam.

The same of the siren, 670 diam. ....

The same of the alpaco, 670 diam.

The same of the elephant, 670 diam.

The same of the goat, 670 diam.

Peculiar concentric corpuscles in blood, 670 diam. .

Coagulated fibrin, 670 diam. ....

The same with granular corpuscles, 670 diam.

Corpuscles of earth-worm, 670 diam.

Circulation in tongue of frog, 350 diam.

The same in web of the foot of ditto, 350 diam.

Corpuscles in vessels of the same, 670 diam. .

White corpuscles in vessels of the same, 900 diam.

Glands of tongue of frog, 130 diam.

Under surfaee of tongue of same, 500 diam.

Red corpuscles of embryo of fowl, 670 diam.

The same, in water, 570 diam. . . .

Red corpuscles of adult fowl, 670 diam.

The same of young frog, 670 diam.

The same of the adult frog, 670 diam.

The same united into chains, 670 diam.

DEVELOPMENT OF EMBRYO OF CHICK.


The cicatricula prior to incubation

The same at the end of first day of incubation

The same at the thirty-sixth hour .

The same at the close of the second day

The same at the end of the third day

The embryo on the conclusion of the fourth day

The same at the termination of the fifth day

The embryo of six days old ....

The embryo of the ninth day of development. .

The same at the end of the seventh day, detached

Ditto at the end of the ninth day, also detached

MUCUS.

Corpuscles of, in their ordinary condition, 670 diam.

The same collapsed, 670 diam

The same, showing the action of water, 670 diam.

The same acted on by dilute acetic acid, 670 diam.

The same after the action of undilute acetic acid, 670 diam.

The same in process of development, 670 diam.

Vaginal mucus, 670 diam. ......

^Esophageal mucus, 670 diam. .....

Bronchitic ditto, 670 diam.

Vegetation in mucus, 670 diam. .....

Mucus of stomach, 670 diam .

Vaginal tricho-monas

PUS.

Corpuscles of laudable pus, 670 diam. .

The same acted on by acetic acid, 670 diam. . .

The same treated with water, 670 diam

Epithelial scales from pustule, 670 diam. . . .

Corpuscles from scrofulous abscess, 670 diam. . . , Vibrios in venereal pus, 670 diam. ....


< 3


MILK.


Globules of healthy milk of woman, 670 diam. . The same of impoverished human milk, 670 diam. Colostrum, 670 diam. .....

Ditto, with several corpuscles, 670 diam.

Globules of large size, 670 diam.

Ditto, aggregated into masses, 670 diam.

Pus in the milk of woman, 670 diam.

Blood corpuscles in the human milk, 670 diam.

Globules after treatment by ether, 670 diam.


The same after the application of acetic acid, 670 diam.


Caseine globules, 670 diam Plate xv. Fig. 5

Milk of cow adulterated with flour, 670 diam. .... " xv. " 6


SEMEN.

Spermatozoa and spermatophori of man, 900 diam. Spermatozoa of Certhia familiaris .....

FAT.

The fat vesicles of a child, 130 diam. .

Ditto of an adult, 130 diam. ......

Ditto of the pig, with apparent nucleus, 130 diam.

Ditto of the same, ruptured, 130 diam. ....

Ditto of marrow of the femur of a child, 130 diam. .

Ditto, with the membranes of the vesicles ruptured, 130 diam.

Crystals on human fat vesicles, 130 diam. ....

Fat vesicles in melicerous tumour, 130 diam.

Ditto contained in parent cells, 120 diam. ....

Ditto after the absorption of the parent cell-membrane, 120 diam.

EPITHELIUM,

Buccal epithelial cells, 670 diam.

Cuneiform ditto from duodenum, 670 diam.

Ciliary epithelium from trachea of frog, 670 diam.

Human ciliary epithelium from lung, 670 diam.

Ditto from trachea, 670 diam. .

Tesselated epithelium from tongue of frog, 670 diam.

Ditto from tongue of triton, 670 diam.

Ditto from serous coat of liver, 670 diam.

Ditto from choroid plexus, 670 diam.

Ditto from vena cava inferior, 670 diam.

Ditto from arch of the aorta, 670 diam.

Ditto from surface of the uterus, 670 diam. .

Ditto from the internal surface of the pericardium, 670 diam

Ditto of lateral ventricles of brain, 670 diam.

Ditto of mouth of menobranchus lateralis, 670 diam.

EPIDERMIS.

Upper surface of epidermis, 130 diam.

Under surface of ditto, 130 diam

Epidermis of palm, viewed with a lens only,

Ditto, magnified 100 diam. ......

Vertical section of ditto, 100 diam. ....

Ditto of one of the ridges, 100 diam. .

Epidermis from back of hand, viewed with a lens A portion of same more highly magnified, 100 diam. Epidermis from back of hand 100 diam. Ditto, viewed on its under surface, 100 diam. Portion of ditto, with insertion of hairs, 100 diam.



" 4


XXI.


" 5


XXII.


" 1


XXII.

Ditto from back of neck, 670 diam. Detached cells of epidermis, 670 diam. Cells of vernix caseosa, 130 diam. Cells of ditto, 670 diam.


NAILS.

Longitudinal section of nail, 130 diam

Ditto, showing unusual direction of striae, 130 diam. Ditto, with different distribution of striae, 130 diam. Transverse section of nail, 130 diam. . . . . Cells of which the layers are formed, 130 diam. and 670 diam. Union of nail with true skin, 100 diam. .


PIGMENT CELLS,

Cells of pigmentum nigrum (human), 760 diam. " xxvu.

Ditto of the same of the eye of a pig, 350 diam " xxvu.

Stellate cells of lamina fusca, 100 diam " xxvu.

Ditto more highly magnified, 350 diam. " xxvu.

Cells of skin of negro, 670 diam " xxvu.

Ditto from lung, 670 diam " xxvu.

Cells in epidermis of negro, 350 diam " xxvu.

Ditto in areola of nipple, 350 diam " xxvu.

Ditto of bulb or hair, 670 diam " xxvm.

HAIR.

Bulb of hair, 130 diam. ....

Root of a gray hair, 130 diam.

Cells of outer sheath, 670 diam.

Portion of inner sheath, 350 diam.

Stem of gray hair of scalp, 350 diam.

Transverse section of hair of beard, 130 diam.

Another section of the same, 130 diam.

Fibres of the stem of the hair, 670 diam.

Apex of hair of perineum, 350 diam.

Ditto of scalp, terminating in fibres, 350 diam. .

Ditto of same with needle-like extremity, 350 diam

Root of hair of scalp, 130 diam.

Another form of same, 130 diam. .

Hair with two medullary canals, 130 diam.

Insertion of hairs in follicles, 100 diam.

Disposition of hairs on back of hand.

CARTILA 6E.


Transverse section of cartilage of rib, 350 diam. Parent cells seen in section of ditto, 350 diam. Vertical section of articular cartilage, 130 diam. Ditto of inter- vertebral cartilage, 80 diam. Cartilage of concha of ear, 350 diam. .



Cells of inter-vertebral cartilage, 350 diam. Section of cartilage and bone of rib, 130 diam. Ditto of one of the rings of the trachea, 350 diam. Ditto of thyroid cartilage with fibres, 130 diam. Cartilage of ossification, 100 diam. Section of primary cancelli, 350 diam. Ditto of same, more advanced, 350 diam. Cartilage of ossification, 350 diam. Section of cartilaginous epiphysis, 30 diam. Ditto of same, with bone, 30 diam. Ditto of same, more highly magnified, 330 diam. Section of cartilage and bone of rib, 130 diam.


Plate xxxi. Fig. 2


XXXI. '


' 3


XXXI.


' 4


XXXI.


« 5


XXXIV.


' 1


XXXIV.


' 2


XXXIV.


' 3


XXXIV.


' 4


XXXV.


' 1


XXXV.


' 2


XXXV.


« 3


XXXV.


' 6


BONE.

Transverse section of ulna, 60 diam.

Cross-section of Haversian canals, 220 diam.

Ditto of same more highly magnified, 670 diam.

Longitudinal section of long bone, 40 diam.

Parietal bone of fcetus, 30 diam.

Portion of same more highly magnified, 60 diam.

Spicula of bone of foetal humerus, 350 diam.

Lamina of a long bone, 500 diam.

Cancelli of long bone of fcetus, 350 diam.

Section of femur of pigeon fed on madder, 220 diam.

Section of epiphysis and shaft of foetal femur, 100 diam,

Transverse section of primary cancelli, 350 diam.

Section of cancelli more advanced, 350 diam.

Ditto of epiphysis and shaft of foetal femur, 350 diam.

Ditto of cartilaginous epiphysis of humerus, 30 diam.

Ditto of same with bone, 30 diam.

The same more highly magnified, 330 diam.

Blood-vessels and medullary cells ....

Section of shaft of foetal long bone, 20 diam.

Ditto of bone and cartilage of rib, 130 diam.


XXXII. '


• 1


XXXII. '


' 2


XXXII. '


' 3


XXXII. '


' 4


xxxiii.


' 1


XXXIII.


< 2


XXXIII.


' 3


XXXIII.


' 4


XXXIII.


' 5


XXXIII.


« 6


XXXIV.


' 1


XXXIV.


' 2


XXXIV.


« 3


XXXIV.


' 4


XXXV.


< 1


XXXV.


" 2


XXXV.


' 3


XXXV.


" 4


XXXV.


' 5


XXXV.


' 6


TEETH.

Vertical section of incisor tooth, seen with lens Tubes of dentine near their termination, 670 diam. A not unfrequent condition of same, 670 diam. Tubes of dentine near their commencement, 670 diam. Oblique section of tubes of dentine, 670 diam. Transverse section of ditto, 670 diam. . Transition of tubes into bone cells, 670 diam. . Dilatation of ditto into bone cells, 670 diam. Section of cementum, 670 diam. Ditto of same traversed by tubes, 670 diam. Ditto of same showing angular cells, 670 diam. Fungus on section of dentine, 670 diam. Oil-like globules on section of same, 350 diam.


xxxvi.


< 1


XXXVI.


< 2


XXXVI.


' 3


XXXVI.


' 4


XXXVI.


' 5


XXXVI.


' 6


XXXVI.


' 7


XXXVI.


« 8


XXXVII.


' 1


XXXVII.


' 2


XXXVII.


« 3


XXXVII.


' 4


xxxvii. ** 5


20


INDEX OF THE ILLUSTRATIONS.


Section of secondary dentine, 350 diam. Ditto of bicuspid tooth, seen with lens only Vertical section of enamel, 220 diain. . Enamel cells seen lengthways, 670 diam. Cross-section of cells of enamel, 670 diam.


Plate xxxvu. Fig. 6 " xxxvu. " 7 " xxxix. " 3 " xxxix. " 4 " xxxix. " 5


FIBROUS TISSUE.

Longitudinal section of tendon, 670 diam. " xxxix. " 1

Transverse section of same, 670 diam. ..... " xxxix. " 2

White fibrous tissue, 670 diam. " xxxix. " 6

Mixed ditto, 670 diam. " xxxix. " 7

Yellow fibrous tissue, 670 diam. ......." xl. " 1

Different form of ditto, 670 diam. " xl. " 2

Development of blood-vessels, 350 diam. . . . ; . " xl. " 3

Areolar form of mixed fibrous tissue, 330 diam. .... " xl. " 4

Blood-vessels of pia mater, 350 diam. " xl. " 5

Development of white fibrous tissue, 670 diam. .... " xliii. " 2

Portion of dartos, 670 diam. ........" xliii. " 3

Section of corpora cavernosa, slightly magnified .... " xliii. " 4


MUSCLE.

Portion of striped muscle, 60 diam. . . ,

Fragment of unstriped ditto, 670 diam. Muscular fibrillee of the heart, 670 diam. Fragment of striped muscle of frog, 350 diam. Fibres and fibrillae of voluntary muscle, 350 diam. Fibres acted on by acetic acid, 350 diam. Ditto in different degrees of contraction, 350 diam. Union of muscle with tendon, 130 diam. Transverse section of muscular, fibres, 350 diam. Fibres of voluntary muscle of fetus, 660 diam. Zigzag disposition of fibres, 350 diam. Striped muscular fibre and fibrillae, 670 diam.


XLI. " 1


XLI.


' 2


XLI.


« 3


XLI.


' 4


XLII.


' 1


XLII.


' 2


XLII.


< 3


XLII.


( 4


XLII.


< 5


XLIII.


• 1


XLIII.


" 5


XLIII.


' 6


NERVES.

Tubes of motor nerve, 670 diam

The same after the action of spirit, 670 diam. The same after the action of acetic acid, 670 diam. Portion of Casserian ganglion, 350 diam. Nerve tubes of cerebellum, 670 diam. Ditto of cerebrum, with clear cells, 670 diam. Varicose condition of ditto, 670 diam. Filaments of great sympathetic, 670 diam. . Cells of gray matter of cerebellum, 670 diam. Ditto of same, inner stratum, 670 diam. Caudate ganglionary cells, 350 diam.

(Spinal cord, Medulla oblongata, Cerebellum.) Ditto from locus niger of cms cerebelli, 350 diam.

Ditto from hippocampus major, 350 diam.

Ditto from locus niger of crus cerebri, 350 diam. .

Pacinian bodies, natural size .

Ditto, magnified 60 diam

A single Pacinian body, 100 diam.

An anomalous Pacinian body ....

Two other anomalous Pacinian bodies

Cells from corpus dentatum of cerebellum, 350 diam.


"late xlv.


Fig


G


" XLV.


"


7


" XLVI.


"


1


" XLVI.


"


2


" XLVI.


"


3


" XLVI.


"


4


" XLVI.


"


5


" XLVI.


"


6


LUNG.

Pleural surface of lung, 30 diam

Ditto, with vessels of first order, 30 diam

Ditto, magnified 100 diam

Section of lung injected with tallow, 100 diam. .

Casts of air-cells, 350 diam

Section of lung injected with size, 100 diam. Pleural surface of lung, with vessels of second order, 100 diam. Section of lung, with air-cells uninjected, 100 diam. Capillaries of lung, 100 diam


GLANDS,

Follicles of stomach, with epithelium, 100 diam. Ditto of large intestine, in similar condition, 100 diam Ditto of same, without epithelium, 60 diam. Termination of follicles of large intestine, 60 diam. Follicles of Leiburkiihn in duodenum, 60 diam. . Vessels of ditto of appendix vermiformis, 100 diam. Ditto of same of stomach of cat, 100 diam. Stomach tubes, cross-section of, 100 diam. Longitudinal view of stomach tubes, 220 diam. . Ditto of the same, 100 diam. ....

Villi of small intestine, with epithelium, 100 diam. Ditto, without epithelium, showing lacteals, 100 diam. Vessels of villi in duodenum, 60 diam. Ditto of same in jejunum, 60 diam. Ditto of same of foal, 60 diam. .... Solitary glands%{ small intestine, natural size Ditto of large intestine, slightly magnified . Aggregated or Peyer's glands, 20 diam. Side view of same, 20 diam. .... Sebaceous glands in connexion with hair, 33 diam. Ditto from caruncula lachrymalis An entire Meibomian gland, 27 diam. . Illustrations of Mucous glands, 45 diam. Parotid gland of embryo of sheep, 8 diam. . Ditto of human subject, further developed, 40 diam. Mammary gland, portion of, slightly magnified


Ditto of same more highly magnified, 198 diam.

Liver, section of, showing the lobules, 35 diam. .

Surface of ditto, showing the intra-lobular veins, 15 diam.

Section of liver showing the hepatic venous plexus, 20 diam

Vessels of portal system, 20 diam. ....

Section of liver, showing inter-lobular vessels, 24 diam.

Surface of liver, showing portal capillary system, 20 diam.

Ditto, showing both hepatic and portal venous systems, 20 diam. ■

Ditto, with both systems completely injected, 20 diam.

Ditto, with portal vein and hepatic artery, 18 diam.

A terminal biliary duct, 378 diam. .

Secreting cells of liver in healthy state, 378 diam

Ditto, gorged with bile, 378 diam.

Ditto, containing oil globules, 378 diam.

Prostate gland, calculi of, 45 diam.

New tubular gland in axilla, 54 diam.

Tubulus of ditto, 198 diam. ....

Ceruminous glands, portions of, 45 diam. .

Sudoriferous gland, tubulus of, 198 diam.

Kidney, tubes of, with epithelium, 99 diam.

Cross-section of elastic frame-work, 99 diam. .

Ditto of frame-work and tubes, 99 diam. .

Section of vessels in tubular part of kidney, 33 diam.

The same vessels seen lengthways, 33 diam.

Tubes with epithelium, 378 diam

Corpora Malpighiana of kidney, injected, 40 diam. Uriniferous tubes of a bird, 40 diam. . . . Corpora Malpighiana of the horse, 40 diam. Inter-tubular vessels of surface of kidney, 90 diam. Transverse section of injected kidney, 67 diam. Uninjected corpora Malpighiana

With capsule, 100 diam.

Without ditto, 100 diam. ....

Malpighian body, more highly magnified, 125 diam. Afferent and efferent vessels of Malpighian tuft, 45 diam Epithelial cells of the tubes, 378 diam.

Testis, tubes of, 27 diam

Tubes of ditto, more highly magnified, 99 diam.

Vessels of thyroid gland, injected, 18 diam. .

Vesicles of ditto, viewed with a lens only .

Ditto of same, magnified 40 diam.

Ditto of same, showing the structure of their walls, 67 diam.

Lobes and vesicles of same in their ordinary condition, 27 diam.

Nuclei of vesicles of thyroid, 378 diam

Follicles of thymus, with vessels, 33 diam

Capsule of ditto, 54 diam. . .

Nuclei and simple cells of same, 378 diam

Compound or parent cells of ditto, 378 diam.

Spleen, nuclei and vessels of, 378 diam


Plate


L1V.


Fig. 6


LIV.


« 4


LV.


" 1


LV.


" 2


LV.


" 3


LV.


u 4


LV.


" 5


LVI.


" 3


LVI.


" 4


LVI.


" 2


LVII.


" 1


LVII.


"2a


LVII.


"2b


LVII.


" 2c


LVII.


" 3


LVII.


"4a


LVII.


" 4b


LVII.


" 5


LVII.


" 4c


LVIII.


" 1


LVIII.


" 2


LVIII.


" 3


LVIII.


" 4


LVIII.


" 5


LVIII.


" 6


LXIX.


" 1


LIX.


" 2


LIX.


" 3


LIX.


" 4


LIX.


" 5


LX.


" 2


"


" A


tt


" B


LX.


"3a


LX.


"3b


LX.


"3c


LX.


" 1


LX.


" 4


LXI.


" 1


LXI.


« 2


LXI.


" 3


LXI.


" 4


LXI.


" 5


LXI.


" 6


lxi:


" 7


lxi:



Supra-renal capsule, plexus on surface of, 54 diam. .

Tubes of ditto, 90 diam

Nuclei, parent cells, and molecules of ditto, 378 diam. Vessels of supra-renal capsule, 90 diam. Pineal gland, compound bodies of, 130 diam. Pituitary gland, cells and fibrous tissue of, 350 diam.


Plate lxii. Fig. 2


ANATOMY OF THE SENSE OF TOUCH,

Epidermis of palm of hand, 40 diam. "

Ditto of back of hand, 40 diam "

Papillae of palm of hand, 54 diam "

Ditto of back of hand, 54 diam. . . . . . . . "

Epidermis of palm, under surface of, 54 diam. .... "

Ditto of back of hand, under surface of, 54 diam. "

Vessels of papilla? of palm of hand, 54 diam. .... "

Ditto of same of back of hand, 54 diam. ....."


LXIII.


tt


1


LXIH.


tt


2


LXIII.


tt


3


LXIII.


"


4


LXIII.


tt


5


LXIII.


"


6


LXIII.


it


7


LXIII.


« 


8


ANATOMY OF THE SENSE OF TASTE.

Filiform papillae, with long epithelial appendages, 41 diam.

Ditto, with shorter epithelial processes, 27 diam.

Ditto, without epithelium, near apex of tongue, 27 diam. .

Ditto, without epithelium, near centre of same, 31 diam.

Filiform and fungiform papilla?, without epithelium, 27 diam.

Peculiar form of compound papillae, 27 diam.

Filiform papillae in different states, 27 diam.

Ditto, with epithelium partially removed, 27 diam.

Follicles of tongue, with epithelium, 27 diam. .

Ditto, without epithelium, 27 diam. ....

Ditto, viewed as an opaque object, 27 diam.

Filiform papillae from point of tongue, 27 diam.

Follicles and papillae from side of ditto, 20 diam.

Simple papillae, with epithelium, 45 diam.

Filiform papillae, with ditto, 18 diam.

The same, viewed with a lens only ....

Side view of certain compound papillae, 20 diam. . .

Simple papilla from under surface of tongue, 54 diam. .

Compound and simple ditto from side of tongue, 23 diam.

A calyciform papilla, uninjected, 16 diam.

Ditto, with the vessels injected, 16 diam. ....

Filiform papillae near centre of tongue, injected, 27 diam.

Ditto near tip of tongue, injected, 27 diam.

Simple papillae, injected, 27 diam. ....

Fungiform ditto, injected, 27 diam. .....


LXIV.


it


1


LXIV.


"


2


LXIV.


"


3


LXIV.


"


4


LXIV.


tt


5


LXIV.


"


6


LXIV.


"


7


LXIV.


"


8


LXV.


"


1


LXV.


"


2


LXV.


"


3


LXV.


"


4


LXV.


"


5


LXV.


"


6


LXV.


"


7


LXV.


ft


8


LXV.


tt


9


LXV.


tt


10


LXV.


"


11


LXVI.


tt


1


LXVI.


"


2


LXVI.


tt


3


LXVI.


"


4


LXVI.


ft


5


LXVI.


tt


6


ANATOMY OF THE GLOBE OF THE EYE.


Vertical section of cornea, 54 diam. A portion of retina, injected, 90 diam. Section of sclerotic and cornea, 54 diam.


LXVII.


tt


1


LXV1I.


ft


2


LXVII.


it


3


24


INDEX OF THE ILLUSTRATIONS


Vessels of choroid, ciliary processes, and iris, 14 diam. Nuclei of granular layer of retina, 378 diam.

Cells of the same, 378 diam

Ditto of vesicular layer of retina, 378 diam.

Caudate cells of retina, 378 diam. ....

Cells of the membrana Jacobi, 378 diam.

Fibres of the crystalline lens; a, 198 diam. ; 6, 378 diam.

A condition of the posterior elastic lamina, 78 diam.

Peculiar markings on same, 78 diam.

Crystalline lens of sheep, slightly magnified

Fibres of lens near its centre, 198 diam. .

Stellate pigment in eye of sheep, slightly magnified

Venae vorticosae of eye of sheep, injected

Conjunctival epithelium, oblique view of, 378 diam.

Ditto, front view of, 378 diam. ....

Ciliary muscle, fibres of, 198 diam.

Gelatinous nerve fibres of retina, 378 diam.

Cellated structure of vitreous body, 70 diam.

Fibres on posterior elastic lamina, 70 diam.

Portion of the iris, 70 diam.

Epithelium of crystalline lens, 198 diam. .

Ditto of the aqueous humour, 198 diam.

Hexagonal pigment of the choroid, 378 diam.

Stellate pigment of same, 378 diam. .

Irregular pigment of uvea, 378 diam.


Plate


lxvii.


Fig. 4


11


LXVII.


" 5


tt


LXVII.


" 6


a


LXVII.


" 7


tt


LXVII.


" 8


a


LXVII.


" 9


"


LXVII.


" 10


"


LXVII.


" 11


»


LXVII.


« 12


"


LXVII.


" 13


« 


LXVII.


« 14


It


LXVIII.


" 1


"


LXVIII.


" 2


"


LXVIII.


" 3


"


LXVIII.


" 5


tt


LXVIII.


" 4


it


LXVIII.


" 6


it


LXVIII.


" 7


tt


LXVIII.


" 8


"


LXVIII.


" 9


it


LXVIII.


" 10


(C


LXVIII.


" 11


"


LXVIII.


" 12


It


LXVIII.


" 13


"


LXVIII.


« 14


ANATOMY OF THE NOSE

Mucous membrane of true nasal region, 80 diam.

Ditto of pituitary region, injected, 80 diam

Capillaries of olfactory region of human fetus, 100 diam.


LXIX.


" 1


LXIX.


" 2


LXIX.


" 12


ANATOMY OF THE EAR

Denticulate laminae of the osseous zone, 100 diam. .

Tympanic surface of lamina spiralis, 300 diam.

Inner view of cochlearis muscle of sheep .

Plexiform arrangement of cochlear nerves in ditto, 30 diam.


VILLI.


Villi of foetal placenta, injected, 54 diam. Ditto of choroid plexus, 45 diam.


LXIX. '


' 3


LXIX. '


< 4


LXIX.


' 5


LXIX.


' 6


LXII. '


' 4


LXIX. '


« 9


Plates "Vm., XVII., and XXXVIII., omitted in the original edition, are likewise here omitted. The same numbers for the other plates are observed, that the figures in both editions may correspond.

The Plates added to the American Edition commence at Plate LXX.


PLATES ADDED


TO


THE AMERICAN EDITION


Corpuscles of lymph, 800 diam Plate lxx. Fig. 1

Corpuscles of chyle, 800 diam. . . . . . . " lxx. " 2

Fat vesicles, injected, 45 diam. ....... " lxx. " 3

Transverse sections of hair, 450 diam. ......" lxx. " 4

Cartilage from finger-joint, 80 diam. ...... " lxx. " 5

Vessels of synovial membrane, 45 diam. ......" lxx. " 6

Injected matrix of finger-nail, 10 diam. . . . . . " lxxi. "

Vessels of tendon, 60 diam. ........" lxxii. " 1

Ditto nearer muscular union, 30 diam. " lxxii. " 2

Lymphatic gland and vessels, 8 diam. ......" lxxiii. " 1

Capillaries and air-cells of foetal lung, 60 diam. .... " lxxiii. " 2

Ditto of same of child, 60 diam. ......." lxxiii. " 3

Ditto of same of adult, 60 diam. ...... " lxxiii. " 4

Branchia of an eel, 60 diam . " lxxiii. " 5

Mucous membrane of foetal stomach, 60 diam. . . . " lxxiv. " 1

Ditto, showing cells and cap. ridges of adult, 60 diam. ..." lxxiv. " 2

Ditto with cells deeper and ridges more elevated, 60 diam. . . " lxxiv. " 3

Ditto showing gastric villi, 60 diam. . " lxxiv. " 4

Villi of duodenum, 60 diam. ....... " lxxiv. " 5

Ditto of jejunum, 60 diam. ........" lxxiv. " 6

Ditto of ileum, 60 diam. ........ " lxxv. " 1

Muscular fibre of small intestine, 60 diam. ....." lxxv. " 2

Appendix vermiformis, 60 diam. ...... " lxxv. " 3

Mucous follicles of colon, 60 diam. ......" lxxv. " 4

Malpighian bodies with uriniferous tubes, of adult, 100 diam. . " lxxv. " 5

Ditto enlarged as in Bright's disease, 100 diam. " lxxv. " 6

Enlarged veins of kidney, first stage of Bright's disease, 100 diam. " lxxvi. " 1

Ditto of same, another view, 100 diam. ..... " lxxvi. " 2

Stellated veins in third stage of same, 100 diam " lxxvi. " 3

Granulation on the surface of kidn ;y, 100 diam. ... " lxxvi. " 4

A tube much dilated, 100 diam " lxxvi. " 5

Sudoriparous glands and their ducts, 70 diam " lxxvii. " 1

Ditto, more highly magnified, 220 diam. ....." lxxvii. " 2


26


INDEX OF THE ILLUSTRATIONS


Mucous membrane of gall-bladder, 50 diam. Transverse section of muscles of the tongue, 45 diam. Terminal vessels in cornea, 45 diam. Cornea of viper, showing its vessels, 45 diam.

Choroid coat of foetal eye, 45 diam

Ciliary processes of eye of adult, 45 diam. Mucous lining of unimpregnated uterus, 35 diam. Ditto of impregnated uterus, 35 diam. .

Tuft of placenta, GO diam.

Papillae of gum, 45 diam

Ditto of lip, 45 diam.

Blood-vessels in mucous membrane of trachea, 45 diam.

Ditto of buccal membrane, 60 diam.

Ditto of mucous membrane of bladder, 60 diam. .


Plate


LXXVII. 1


<ig. 3


LXXVII.


" 4


LXXVIII.


" 1


lxxviii.


" 2


LXXVIII.


" 3


LXXVIII.


" 4


LXXVIII.


" 5


LXXVIII.


" 6


Lxxrx.


" 1


LXXIX.


" 2


LXXIX.


" 3


LXXIX.


" 4


LXXIX. LXXIX.


" 5

Introduction

By The Editor.


The object of the present Introduction is to furnish some practical hints on Manipulation in Microscopic Anatomy, so that the student who is disposed to pursue for himself this subject, and has not at his command other authorities, may be provided with the information necessary to commence his investigations.

Although plates and models are useful as companions in study, and as giving more explicit views of authors than can be done in words, yet as these, however excellent, can never make the student master of special anatomy without dissection, so in the more intricate department of minute anatomy, he who would there become a proficient, must investigate for himself.

The same remarks apply in a manner to specimens prepared by others : these seldom receive that close study and repeated investigation which are willingly given to one's own attempts. The very admirable preparations of different tissues by Hett, Topping, Darker, and others, which may now be purchased of many opticians, should be rather regarded as standards of success, with which the student may compare his own efforts, than as substitutes for his own manipulation.

For distinctness, it is proposed to treat the subject under three divisions :

I. Microscopes and their Accessory Instruments. II. The Preparation of Objects. III. The Preservation of Objects.

I. Of Microscopes and their Accessories

It will not fall within the design of this introduction, to treat either of the theory of the microscope, or its construction. A brief description of the various forms in present use is all that will be necessary.

Those only who have studied with the microscope, know the comfort and satisfaction of using a good one; and by this is meant excellence not only in object-glasses, although these are the most essential to a good microscope, but excellence in all the details of accessory instruments, and in nice mechanical adjustment.

It is a very common error to suppose that cheap microscopes will answer as well for low powers as more expensive ones : that, for instance, there is no difference in a one-inch object-glass and common eye-piece of an ordinary microscope, and the same focus object-glass and eye-piece of a good instrument : hence many persons, about commencing the study of microscopic anatomy, and believing that, for the study of injected preparations, a power of one hundred diameters will in most cases answer, purchase the cheapest instrument they can obtain, with that degree of magnifying power, unaware that penetration and definition are qualities that an object-glass needs, even more than mere magnifying power — qualities that are rarely found to exist in any degree in the cheaper microscopes.

It is in these qualities that the English and American instruments excel the French and other continental microscopes : an observer with the former being able actually to see more of, and see better, the construction of an object with a glass of much lower magnifying power : the object being in the latter case clear and well defined, while in the other, though more highly magnified, blurred and indistinct with poor illumination. It is a great satisfaction in viewing an object with a microscope to be able to see it as well as any one has hitherto seen it : if not able to do this, one always feels at a disadvantage.

An error, somewhat similar, committed by beginners, is in supposing that a low-priced microscope (and usually therefore a poor one) is sufficiently good to commence with, and that a more perfect instrument with higher powers may be purchased when more familiar with its use. This is not only poor economy, but, as already stated, such an instrument gives unsatisfactory and often false views : it being much better economy where this is regarded, and infinitely more satisfactory, to purchase a good instrument with low powers at a fair price, to which the higher powers may be added as means allow. Those who can afford a good microscope, and yet purchase a poor one, commence their studies under great disadvantages.

It must not be forgotten, however, that in microscopic observation, more depends on the observer than upon the instrument ; more upon the practised eye, and the analytical mind, than upon the precise form of the microscope or the number of its accessories.

The following brief enumeration of the different prominent microscopemakers may be of service to persons at a distance about to order a microscope, and who are embarrassed by the number of manufacturers, and uncertain about the expense.

At the present time, the most elaborate and completely furnished micro


MICROSCOPES, ETC. 29

scopes are those of English, and especially of London manufacture. A full account of the various forms by the three principal London makers, is given by Mr. Quekett in his " Practical Treatise on the Microscope." He, however, does not give preference to either. — Mr. A. Ross, No. 2 Featherstone Buildings, Holborn, London, is usually considered the most prominent of the London makers, having done more by his contributions to the literature of the microscope, and his various improvements in its form and accessory apparatus, than either of the other makers. His best or largest microscope has been considered to be unsurpassed by any in the world. Its price in London, when complete, is about $450 ; the duty on importation into this country being 30 per cent, ad valorem. As has been mentioned in the preface to the English edition of the present work, most of the objects represented, are engraved as viewed with one of Mr. Ross's microscopes. Mr. Ross makes several forms of instruments, among which the most reasonable in price, and convenient for use, is one described in the Penny Cyclopedia, article "Microscope."

This instrument, with object-glasses as high as ith-inch,* with the usual accessory instruments, may be obtained in England for about $175.

Messrs. Powell and Lealand, No. 4 Seymour-place, Easton-square, London, have of late years almost, if not quite, equalled Mr. Ross in the excellence of their microscopes, and also construct several forms. One of the steadiest and most convenient is the second size described by Mr. Quekett, on page 77 (figure 44) of his "Practical Treatise."

The price of this instrument complete is about $350 in London, and to those desiring a high-priced instrument the writer can safely recommend this one, as combining great steadiness, accuracy of adjustment, and excel

  • Note. — As these fractions of an inch — ith, |th, ^th, &c. — as applied to the

focus of object-glasses, constantly recur in this introduction and elsewhere, it should be stated that these measurements do not represent the actual distance between the object and the object-glass in each particular case, but are used to signify what the distance would be, if a single lens were used possessing the same magnifying power, instead of a combination (most object-glasses being composed of three lenses instead of a single one, and called a triplet) : in other words, a single lens, to produce the same magnifying power as a ^th-inch triplet, would have to be a lens of |th-inch focus. This nomenclature is unfortunate, because many are misled by it. It is, however, in general use in England and in this country. The following table gives the magnifying powers in diameters of Mr. Ross's object-glasses with the different eye-pieces. The objectives of other makers do not vary much from these :

OBJECT-GLASSES.


EYE-GLASSES.


2-IN.


1-IN.


flN.


|-m.


fm.


t¥™


A. or long eye-piece, . .


. 20


60


100


220


420


600


B. or middle eye-piece, .


. 30


80


130


350


670


870


C. or short eye-piece, . ,


. 40


100


180


500


900


1400


30 INTRODUCTION.

lence in object-glasses. It is a most luxurious instrument to use. Powell and Lealand construct another microscope, having the supports of the compound body and the stage made of iron. This mounting of course considerably reduces the expense, but does not diminish its value as an efficient instrument. In this form the lever-stage is usually employed, and a microscope of this description, with object-glasses as high as ith, may be imported for about $100 ; but this sum does not include any of the expensive accessories, such as the achromatic condenser or camera lucida. Powell and Lealand have sent several of these instruments to this country, and they have given great satisfaction.

Messrs. Smith and Beck, No. 6 Coleman-street (city), London, though less prominent than either of the preceding makers, construct several excellent microscopes; one especially, known as the "Student's Microscope," is highly to be recommended on account of its reasonable price ; being furnished complete with all the accessories for about $200, and combines great steadi ness and convenience in use. The same instrument with plain stage and object-glasses as high as ith, but without the accessories, may be had in London for $75.

Of the French microscope-makers the most prominent have hitherto been M. Chevalier (163 Palais Royal, Paris,) and George Oberhauser. Chevalier's instrument is of the horizontal form, but capable of being converted into the vertical or the inclined one. Though the microscope-stand and apparatus are of good construction, the object-glasses are usually defective in definition : such at least is the character of most of those imported in this country. The horizontal form, recommended by Sir David Brewster as being the best adapted for accurate observation, is to many persons fatiguing to the eye ; and the image of the object being a reflected one, it would appear as if some sharpness of outline must be lost by the reflection. The price of one of Chevalier's best instruments in Paris is about $200. The accessory apparatus is not so complete as with the English instruments.

A smaller size, similar in construction, and usually known as the "small Chevalier," can be obtained at about half the price of the preceding instruments; it is not, however, so complete in object-glasses or accessories.

The form that Mr. Oberhauser (No. 19 Place Dauphine, Paris,) adopts is the vertical one ; a form of construction at once the cheapest and least complicated. His microscopes, though often ordered from this country, and much used on the continent of Europe, have two important faults; the first, in common with M. Chevalier's, want of definition and penetration in the objectglasses, and the second, inconvenience of mechanical arrangement, especially in the means of illumination ; the mirror always being too small, and incapable of affording oblique light. M. Oberhauser seems to rely more on his short eye-pieces for increasing the magnifying power, (there sometimes


MICROSCOPES, ETC. 31

being five or six of these furnished with his microscope,) than upon his objectglasses ; a great mistake, and always attended by loss of light and definition. The more one studies with the microscope, the more one learns to rely on the object-glass for power and less on the eye-piece ; objects being rarely seen so clearly, and therefore not so well, with a very short eye-piece as with one from two to three inches long. Views of objects afforded by M. Oberhauser's combination of object-glass and short eye-piece, producing according to his own table a magnitude of 900 diameters, are far less satisfactory, and show less of minute structure, than the same object seen with an English ^th object-glass and long eye-piece, producing a magnitude of not more than 220 diameters. A microscope is furnished by M. Oberhauser at about six months' notice for $100, with a power according to his own measurement of 900 diameters.

At present, the best French microscope-makers are M. Nachet and M. Brunner, both of Paris. The microscopes of Nachet (Rue Serpente, No. 16,) much resembles in general form and arrangement the large-sized instruments of M. Oberhauser, their excellence consisting in the superiority of their object-glasses : they are much employed in microscopic investigations in Paris, and are good working instruments ; the prices are about the same as Oberhauser's, but the object-glasses are every way superior.

His largest sized instrument, complete, is sold in Paris at 650 francs. His smallest size, at 100 francs: between these, are several intermediate sizes.

The microscope of M. Brunner (Rue des Bernardins, No. 34, Paris,) is also a vertical one, but possesses more advantages of mechanical arrangement than any other of the same construction ; indeed, it almost equals the more expensive form usually adopted in England, for convenience of arrangement and facility in use. The stage is large, and has not only a circular motion, but also two lateral motions, made by adjusting-screws; the mirror is large, and admirably arranged for affording oblique light. The object-glasses supplied with this instrument are excellent, and for sharpness of definition and light, are hardly surpassed by the best English ones. M. Brunner also supplies the achromatic condenser, the polarizing apparatus, and other accessories, to those who wish them ; and his prices for his best instruments vary from $90 to $150, according to the powers of the object-glasses and accessories furnished. The writer has no hesitation in recommending these microscopes as the best of the vertical form, possessing, as already mentioned, more advantages of mechanical arrangement than any other, and the objectglasses are not excelled by any of continental make.

The rapid advances made of late years in microscopic knowledge, have been owing, in a great measure, to improvements in the construction of object-glasses. To this end, perhaps nobody has contributed so much as Mr. Charles A. Spencer, of Canastota, New-York. The objectives made


32 INTRODUCTION.

by this gentleman may safely bear comparison with the best of foreign make, and for sharpness of definition, power of penetration, and large angle of aperture, are not excelled by any in the world. As has been already stated, much of the excellence of an object-glass depends on its power of penetration : this, again, depends in a great measure on the angle of aperture by which the rays of light from the object enter the glass. It must be evident that the greater the angle, the larger must be the pencil of rays. Mr. Spencer has made some valuable experiments on this subject, and has been enabled to obtain a curve for his object-glasses, by which in the yjthinch, he can give an angle of aperture of 160°. This is believed to be the largest angle ever given to an object-glass : the greatest obtained by Mr. Ross, was, for a T y;h> an angle of 135°, and the one usually given to object-glasses of the same focus by the best foreign makers, not greater than 120°. In Mr. Spencer's ith-inch object-glass, the angle of aperture is 85° ; in the -i-th-inch, 135° ; in the objectives of foreign make, according to Mr. Quekett, the angles are for the ^th-inch, 63 s , and the |th-inch, 80°.

To Mr. Spencer is due the credit of having first resolved, with lenses of his own construction, the fine markings on the Navicula Spencerii and Grammatophera Subtillissima : these minute shells have since been adopted by microscopists as test-objects for the highest powers. The Navicula Spencerii, will exhibit one set of lines with Mr. Spencer's ith-inch objectglass : both sets with the |th-inch. The Grammatophera Subtillissima is a good test for a T \ih or T Vth.

Of several microscopes made by Mr. Spencer, two or three only will be here noticed. His first-class or best instrument is mounted on trunnions, and embraces all the acknowledged improvements, in form and stage, whereby the greatest steadiness and freedom from tremour are secured. The price of this instrument, with all the accessories and full sets of objectglasses, will approach $350.

The second-class instruments, complete as to object-glasses and accessories, but mounted less expensively, cost from $200 to $250.

A very efficient microscope, is one known as the "Pritchard form:" this instrument has been somewhat modified by Mr. Spencer, and where a less expensive instrument than either of the others is desired, this one will be found a good working instrument, and available for all purposes of anatomical study. The cost of this form, with object-glasses as high as the ith with the usual accessories, is from $125 to $150.

Mr. Spencer also makes some simpler forms of instruments, and yet very efficient working ones, with objectives as high as ith, the price of which does not exceed $75.

Mr. Spencer has experienced some delay in the completion of his establishment, owing to the difficulty of obtaining efficient workmen, the business


ACCESSORY INSTRUMENTS. 33

being in this country comparatively a new one, and for which it was necessary to educate men and invent tools. These difficulties are now overcome, and his establishment is in active operation.

Mr. J. B. Allen, of Springfield, Mass., has constructed several microscopes which are said to have been very good instruments, both as to model and object-glasses. The form is somewhat after the Pritchard model, in which the body inclines to any angle : the object-glasses yet made have been chiefly of low and medium powers, and have performed very satisfactorily.

Messrs. Pike and Sons, opticians, of New York, construct a microscopestand of great steadiness and convenience for use, the supports and general appearance of which much resemble the large instrument of Mr. Ross. The stage is large, being nearly four inches square, and moveable either by adjusting-screws, and revolving after the plan described by Mr. Legg, or is made moveable by a lever, as sometimes employed by both Powell and Lealand, and Smith and Beck. This latter stage movement is very exact, and allows of quick or slow motion in any direction.

The mirror is large, being about three inches in diameter, and admirably arranged for oblique light; the quick motion is effected by rack-work, and the slow motion by means of a conical-pointed steel screw, pressing against the top of a slit in an inner tube, furnished with a spring : at the end of this tube, the object-glasses are adapted.

The instrument is of considerable weight, which adds to its steadiness, being at the same time well proportioned. Its price, with eye-pieces, all the accessories, and without object-glasses, is about $100.

ACCESSORY INSTRUMENTS.

There are several instruments accessory to the microscope, and most useful in dissection, in addition to those usually furnished with the instrument.

1. Scalpels. — The scalpels of the dissecting-case of the Medical Schools will be necessary in making the ordinary sections, but for very minute dissection, much smaller-sized instruments will be found useful. The blades of these may be either straight, curved, lancet-shaped, or probe-pointed. In default of any instruments for this especial purpose, the small knives furnished with the case for operations on the eye, may be employed.

2. Dissecting Forceps. — Small-sized forceps, both straight and curved, are among the instruments most often required in minute dissections. Those with exceedingly fine points, and at the same time made true, are especially useful. The more serviceable forms are here represented :


34


INTRODUCTION,



Fig. 1.


A very convenient form of forceps, is one known as the cutting-forceps, and is represented by figure 2 :



Fig. 2.

The sides of this instrument are riveted at the end, as those of the ordinary forceps, but the cutting part consists of two scissor-shaped blades, which overlap each other, and are prevented from crossing over too far by a small steel pin ; the blades are bent at an angle with the sides, and by this means the instrument can be very conveniently employed for dissecting under a lens of half an inch focus. An instrument somewhat resembling this, and called the microtome, is represented at figure 3 :



"It consists of two sides, like a pair of dissecting-forceps, but each terminated by a scissor-shaped blade, arranged so that its cutting-edge is perpendicular to the broad surface of the sides, in order to prevent the blades from opening too wide; a screw


ACCESSORY INSTRUMENTS. 35

with a fly-nut is attached to one blade, and the other moves freely upon it; the screw is also provided with another nut, situated between the blades; the latter may be adjusted so as to prevent the blades from being closed beyond a certain point, while the former serves to regulate the space, that the blades may be kept open by the spring." *

This instrument is a very useful one, on account of the great precision with which any tissue or filament may be cut, independent of any tremour of the hand, and without deranging the preparation.

3. Dissecting Needles. — These instruments are necessary in carrying on dissection of delicate tissues under the microscope. They may be either curved or straight, and of different sizes. Messrs. Pike and Sons, opticians, of New York, furnish, at a very small cost, needle-holders, in which the needles may be changed as often as the points become broken, or otherwise unfit for use. Straight needles may be curved by heating them in a spiritlamp to a red heat, and then giving them the desired curve : they should be then again heated, and dipped in cold water to harden them.

4. Valentin's Knife. — This instrument, used in making thin sections of soft animal tissues — like the liver, spleen, &c. — is a double-bladed knife, the flat parts of the blades being placed against each other, and adjusted by a screw, placed below the cutting portion of the blades. The form of this knife is given at figure 4, and is thus described by Mr. Quekett :

JiiiiK


Fig. 4.

"This consists of two double-edged blades, one of which is prolonged by a flat piece of steel to form a handle, and has two pieces of wood riveted to it for the purpose of its being held more steadily; to this blade another one is attached by a screw; this last is also lengthened by a shorter piece of steel, and both it and the preceding have slits cut out in them exactly opposite to each other, up and down which a rivet, a, with two heads, is made to slide, for the purpose either of allowing the blades to be widely separated or brought so closely together as to touch ; one head of this rivet is smaller than the hole in the end of the slit, and can be drawn through it, so that the blade seen in the front of the figure may be turned away from the other, in order to be sharpened or to allow of the section made by it being taken away from between the blades. The blades are constructed after the plan of a double-edged scalpel, but their opposed surfaces are either flat or very slightly concave, so that they may fit accurately to each other, which is effected more completely by a steady pin seen at the base of the front blade. When this instrument is required to be used, the thickness of the section about to be made will depend upon the distance the blades are apart; this is regulated by sliding up or down the rivet, a, as the

  • Quekett's " Treatise on the Microscope."


36 INTRODUCTION.

blades, by their own elasticity, will always spring open, and keep the rivet in place; a cut is then to be made by it, as with an ordinary knife, and the part cut will be found between the blades, from which it may be separated, either by opening tliem as wide as possible by the rivet, or turning them apart in the manner before described, and floating the section out in water."

Mr. Hernstein, cutler, of New York, has made a modification of this instrument, by making the handle curved instead of straight: this form has the advantage of enabling the operator to hold it more firmly while making the section ; it has the disadvantage of not allowing him to use the cuttingedges on the concave side of the curved handle, without bringing the tissue to be cut to the edge of the table, so that the handle has room to play below it. Those who have not at hand one of these instruments, and cannot procure one, may make the thin section with a sharp scalpel or a thin razor.

5. Troughs. — Many delicate dissections are carried on underwater; for this purpose, troughs are necessary on which to place the tissue to be dissected. The most convenient are those made of a metal frame, about three inches Ions:, two wide, and one inch deep, with a glass bottom, so as to transmit the light when necessary. If desired, the under surface of the glass in one of the troughs may be blackened with sealing-wax-varnish, or a piece of black silk or common court-plaster pasted on.

In default of this form of trough, any small vessel of glass, porcelain, or metal may be employed ; a small evaporating-dish answers extremely well. If it is necessary to observe the object by means of transmitted light, of course only a glass trough will answer the purpose. One larger trough, four or six inches square, having a piece of flat cork half an inch thick, (covered with black cloth, if desired,) and secured to the bottom by means of the marine glue, or the compound cement, so that the tissue under dissection can be fastened with pins to the cork, will be found especially useful. In this form of trough, dissections of entire insects, such as beetles, common cockroaches, &c, can be carried on.

6. The Compressor. — This is an instrument by means of which pressure may be applied at will to an object under examination with the microscope ; various forms are in use, but the simplest and most effectual is the one represented in figure 5 :




Fig. 5.


PREPARATION OF OBJECTS. 37

" This instrument consists of a plate of brass, three or more inches long and one and a half broad, having in its middle a circular piece of plate-glass for an objectholder; this is slightly raised above the metal plate; at one end of the latter is a circular piece of brass, having attached to it another piece of brass, carrying an arm capable of being moved up and down, by means of a screw at one end, while at the other is a semi-circle, supporting by screws a ring of metal, to the under side of which, a piece of thin glass is cemented." *

The use of the instrument is to produce a pressure upon the object between the plates of glass while being examined with the microscope ; the compressor being placed upon the stage of the instrument. The object is placed upon the under plate of glass, the arm being made to turn away for that purpose.

7. Pipettes. — These are fine glass tubes, about eight or nine inches in length, either straight, and of the same calibre throughout, or curved or drawn to a fine point by means of heat from a spirit-lamp. They are useful in applying the different reagents to the objects under examination, and also for collecting any required portion of fluid — as urine, pus, &c. — and placing it in the desired position for examination. They are among the most useful of the minor accessory instruments, and can be fashioned in any shape by the student himself.

A few only of the accessory instruments that may be used in minute anatomy have been here described. There is much truth in the observation of Rudolph Wagner, that the more one observes with the microscope, the more he learns to rely on the simplest instruments; the complicated ones giving usually more trouble than assistance. Still, there are circumstances in which a timely use of the instruments just described will be found of great assistance.

II.— PREPARATION OF OBJECTS.

It is designed to give but few directions for the preparation of objects for the microscope in this place : particular directions in manipulation, for those objects requiring an especial method of treatment, will follow the articles in the text.

1. Fluids. — Fluids, such as blood, urine, &c, require but little preparation : a small portion of the fluid to be examined is placed on a plain glass slide by means of a pipette, and is then covered with a small piece of thin glass. This latter direction should be always followed, otherwise there will be the two-fold danger of soiling the object-glass, if a high one be used, by inadvertantly touching the fluid under examination, and also of allowing the

  • Quekett's "Practical Treatise."


38 INTRODUCTION.

vapour of the fluid to condense on the object-glass, and thereby occasion an indistinctness of vision and want of definition. Care must be taken not to place too great a quantity of the fluid on the slide at first; one small drop is usually sufficient. When dilution is necessary — and most of the fluids, blood, lymph, &c, are better examined when diluted — the serum of the blood or albumen, may be employed ; in most cases, water cannot be employed on account of its reacting properties.

Fluids generally require higher powers for examination than solid preparations. They may be first viewed with a ith-inch object-glass and then with a |th. Any of the reagents may be introduced, without removing the thin glass, by means of a pipette containing the reagent placed at one edge, and a little of the fluid allowed to escape. This will be found to insinuate itself under the glass by means of capillary attraction, and the effects should be observed with the microscope.

2. Solids. — These usually require more care in their preparation for examination than fluids. The hard solids, as bone, require to be cut in thin sections, and sometimes polished before their structure can be discovered. Particular directions for each preparation will be given at the close of the chapters treating of their anatomy. The soft solids may be examined either in their recent condition or be treated by various chemical agents, or be farther prepared by injection. The treatment best calculated to display the structure of each particular tissue will hereafter be given.

For making thin sections of the soft solids, the Valentin's knife or a sharp scalpel may be used. The compressor, the small scalpels, the dissecting needles, and the troughs for dissection will be constantly required.

Objects examined in this condition require for the most part very low powers. If the compound microscope be used, a one or two-inch objectglass will be power high enough. In many cases, the simple microscope will be most efficient. In some instances, the same parts of the object require to be examined with successive powers as high as the ith-inch object-glass. The most difficult, as well as the most beautiful method of exhibiting the structure of certain tissues, is by fine injection.

3. Injections. — The chief objects of minute injections are to determine the vascularity of a tissue ; the relative order, size, and arrangement of arteries, veins, and often-times lymphatics, and to trace the final distribution of the larger blood-vessels in the capillaries. It will be found that different structures will present different arrangements of these vessels, always coinciding with the differences of function.

To demonstrate these variations of structure, it is necessary that the injection should be perfect and complete. The operation is a delicate one, and


OF INJECTIONS. 39

to succeed perfectly, requires some practice ; a few attempts, however, will convince any one how much may be attained by perseverance. Experiments may first be made in comparative anatomy, and the different organs of sheep, &c, may be always easily obtained ; and these not only afford beautiful specimens of microscopic anatomy, but for the most part are as difficult to inject as the same organs in the human subject, and are on that account very good practice.

That an injection may succeed well, it is necessary, that some time should elapse after death before the operation be attempted. It is well known that immediately after death, a certain contractility of the vessels takes place, which would prevent the perfect penetration of the material injected : we must therefore wait for the relaxation of this contraction. The best time for injecting is in summer, about twenty-four to thirty-six hours after death, and in winter, about three days. These are general directions, which may be changed according to the especial circumstances of the case, and the condition of the organ to be injected. It would be a still greater error to wait too long a time ; for the softened vessels would certainly be ruptured, and extravasation of the injected material follow. This, if extensive, would not only spoil the beauty of the preparation, but completely defeat the object of the injection.

A serious obstacle to perfect injection is the presence of coagulated blood and other inatters in the vessels, more especially in the veins. This point has not been sufficiently regarded in minute anatomy, but it must be evident that if those obstacles which irregularly contract the calibre of the vessels could be removed, the chance of success would be much greater. A necessary step therefore, preliminary to injection, is to wash out the bloodvessels; this may be done by injecting tepid water or sulphuric ether, when this latter agent enters into the composition of the injecting material. It is also of great advantage to place the body or organ to be injected in a warm bath for six or seven hours previous to the operation. The temperature should be about 100° to 106° Fahrenheit. For small organs, when removed from the body, less time will be required.

As there are several points worthy of being noted in the injection of arteries and of veins, the two orders of vessels will be separately noticed.

Injection of Arteries. — As a general rule, the complete injection of the capillary vessels, by means of the arterial trunks, is more difficult than by the veins, for the reason that the arteries are less numerous and of less calibre than the veins. In the lungs, this disproportion does not exist; but here, according to the experience of Rossignol, mentioned at the end of the article on the lungs, the best injections are made by the pulmonary veins. The arteries have the advantage of requiring less preparation than the veins, and


40 INTRODUCTION.

of being always ready; they are also more empty of coagulated blood, and less liable to rupture, owing to the greater thickness of their walls.

Injections by the arteries should be made not by the aorta, because too many vessels would be divided in reaching it, but by the large arteries, which are accessible; as the carotid, brachial, crural, &c. If the injection be made by the aorta, the visceral trunks should be first ligatured.

Injection by the Veins. — On the other hand, the veins present an obstacle to perfect injection in their numerous valves ; it being almost impossible to fill the vessels by one operation, owing to the repellant valvular action. In this operation, it is sometimes necessary to inject a very liquid material first, and after this has somewhat set, as the term is, then to inject more of the same material, but thicker. The proportions for these divisions are about one-third of the solid material to be injected at first, and the remaining two-thirds in the second operation.

Another difficulty in injecting by the veins is their tendency to rupture; this can only be prevented by using a moderate degree of force. The existence of the coagulated blood in the veins has been already alluded to. Inferior animals, to be injected by the veins, should be bled to death, and the veins by which the injection is to be made, opened. The veins of the extremities are usually injected by the superficial lateral internal and external trunks ; when the chylo-poietic viscera are to be injected in situ, the vessels are to be filled from the vena portse just before it enters the transverse fissurb of the liver.

In either order of vessels, the opening for the canula of the syringe should be a mere slit corresponding to the long diameter of the vessel, and not transversely.

A young and lean subject will be found the best for perfect injection, where this can be a matter of choice.

SYRINGE.

The first minute injections were made by Swammerdam, who taught the art to his friend Ruysch, (born in 1638, died in 1731,) and who improved upon Swammerdam's method.

These injections led to many discoveries, and propagated many errors. The instrument employed by Swammerdam is still in general use in the medical schools, and known as Swammerdam's syringe.

For making extensive injections, this instrument will answer every purpose ; for injecting small organs and parts of the extremities, smaller instruments must be employed. Swammerdam's syringe consists of two main parts — the syringe proper and the canula or pipe. The canula is fastened in the nozzle of the syringe by means of a bayonet-catch, and is of course


SYRINGES. 41

removeable at will. A modern improvement is to add a flexible tube to the canula, so that, in the operation of forcing the injection, no injury will happen to the vessel in which the canula is fixed, and no derangement of the parts of the subject on the table. The canulas are of different sizes, to correspond with the calibres of the vessels into which they are to be inserted.

A syringe invented by Charriere, of Paris, which works with remarkable ease and exactness, owing to the arrangement of the discs of leather which form the piston, is advantageously used in making injections with smaller quantities; with this syringe also are canulas of different sizes.

These syringes, with other instruments of Charriere's manufacture, useful in microscopic manipulation, may be purchased at Mr. H. Balliere's foreign book-store, No. 219 Fulton-street, New York. Many other forms of syringe are in use, and all have their advocates ; but in general, any form in which the working of the piston is perfectly true, and at the same time easy, will, with proper care and attention to the exclusion of air, &c, answer very well. The writer has made some good injections of small organs with the ordinary ear-syringe, which is also capable of having canulas of different sizes attached to it. Some of the many forms of patent syringes sold at the druggists for making ordinary enemata, may be advantageously employed, especially when the material of the injection is very fluid, as in the method by double-decomposition, hereafter to be noticed. These instruments would all require certain adjustments in the arrangement of canulas which the student could himself make. One form of these enema-syringes, in which the jet is continuous, and not saltatim, as in the forcing-pump, is the best, and the syringe can be constantly supplied with the injecting material, if necessary, by an assistant, without suspending the operation. One objection to this instrument is, that any accident that may happen during the operation, such as rupture of a vessel, cannot be appreciated as readily as when the piston is guided by the hand. In ordinary injections, as already stated, the part to be injected should be placed some hours in warm water, before the operation be attempted. The syringe, canula, and injecting material, should be moderately heated. If the injection is to be by the veins, and by these we are usually more successful than by arteries, the canula, with the flexible tube, is to be secured in the vessel previously incised longitudinally, and the canula secured by a ligature: a second ligature should lie loose upon the canula to secure the vessel when the operation is finished. The vein may then be washed out by an injection of warm water; at least half an hour should elapse, to allow the vessels to empty themselves, before the injection be proceeded with. As it is important to exclude all air in the operation, the tube and canula should be first filled with the fluid material, the tube be tightly


42 INTRODUCTION.

corked, and the canula secured in the vessel. The next step is to fill the syringe, and secure the tube by the bayonet-catch. The injection may then be commenced, with a force, depending somewhat on the thickness of the material employed ; the thinner the fluid, the less force will be necessary. When it is recollected how slight is the muscular force of the heart, it will be easy to conceive how little force will be necessary to fill the vessels in favourable circumstances.

When a rupture of a large vessel occurs during the injection, and this can be known by the greater ease with which the material enters, the operation must be suspended and the vessel secured. If the vessel itself cannot be isolated, a ligature may be applied, including a portion of the tissue surrounding it. If rupture of the capillaries takes place, the operation need not be suspended, but pressure in the neighbourhood of the suspected rupture may be applied, and the injection must be continued rather longer than when no such accident has occurred.

The injection being finished, time must be allowed for it to set, when the dissection may be commenced. Many patches will be found more perfectly injected than others; and the proportionate success can only be known by inspection with the microscope.

When the minutest capillaries are not injected, the preparation may still be useful in displaying the second order of vessels.

Mucous membranes require to be soaked in water or washed with a syringe, to free them from epithelium and mucus.

The minute dissection of injected tissues is best conducted in water, by means of the trough and dissecting needles.

In conclusion, it may be observed that the operation of minute injection, when properly performed, occupies from one to five hours, according to the size of the specimen and the quantity of material required.

No haste should be used, for unless the material be properly prepared, and the vessels carefully filled, one may be certain of partial or complete failure.

MATERIALS. Many substances have been employed as the bases of fine injections, but as the result depends more on the medium by which the solid part of the injection is conveyed into the vessels, the most useful forms will be here noticed in turn.

1. Injections with 'Turpentine. — In this method, materials used as paints of various colours, are first finely ground in linseed oil, then largely diluted with oil of turpentine. The paints most used for imparting different colours are : Vermilion, Chrome Yellow, Prussian Blue, White-lead. In making injections with these paints, too much importance cannot be attached to their


INJECTING MATERIALS. 43

being ground to the utmost possible fineness; otherwise the colouring particles of the injection cannot penetrate the capillaries.

These paints, already finely ground, can be procured at the stores where "artist's materials" are sold, or they can be prepared in a "paint-mill" or on a house-painter's slab.

The proportion of the ground paint to the oil, varies with the intensity of of the colour; but the following scale will usually answer: For Vermilion, •jL-th part of whole mass by weight; Prussian Blue, ^i^th; Chrome Yellow, T i u th ; White-lead, y i ? th.

If it be found that the proportion of blue makes the injection too thin, the blue may be first well mixed with the white-lead, and then a larger proportion of the mixed paint employed. When too much blue is used, the colour produced is nearly black, and therefore too strongly absorbent of light.

These injections require to be but slightly warmed, and in summer this process may be entirely dispensed with.

When injections by this method are successful, the colours soon harden, and are well preserved for a long time. The plan is the only one recommended by M. Robin, and is much in vogue in Europe.

2. Injections with Ether.— To Dr. P. B. Goddard, of Philadelphia, is due the merit of having first employed ether in minute injections; his method is described by him in the Medical Examiner of Philadelphia for December, 1849, and is here quoted:

"For the purpose of making such an injection, the anatomist must provide himself with a small and good syringe; some vermilion, very finely ground in oil; a glassstoppered bottle, and some sulphuric ether. The prepared vermilion paint must be put into the ground-stoppered bottle, and about twenty or thirty times its bulk of sulphuric ether added; the stopper must then be put in its place, and the whole well shaken. This forms the material of the injection. Let the anatomist now procure the organ to be injected, (say a sheep's kidney, which is very difficult to inject in any other way, and forms an excellent criterion of success,) and fix his pipe in the artery, leaving the rem open. Having given his material a good shake, let him pour it into a cup, and fill the syringe. Now inject with a slow, gradual and moderate pressure. At first, the matter will return by the vein coloured, but in a few moments this will cease, and nothing will appear except the clear ether, which will distil freely from the patulous vein. This must be watched, and when it ceases, the injection is complete. The kidney is now to be placed in warm water of 120° Fahrenheit, for a quarter of an hour, to drive off the ether, when it may be sliced and dried, or preserved in alcohol, Goadby's solution, or any other anti-septic fluid. For glands, as the kidney, liver, &c, it is better to dry and mount the sections in Canada balsam : but for membranous preparations, stomach, intestine, &c, the plan of mounting in a cell, filled with an anti-septic solution, is preferable."


44 INTRODUCTION.

In this method, as in the preceding one, much depends on the fineness of the colour used. The writer has examined many of Dr. Goddard's injections with ether, and can bear witness to their perfect success.

When the ether injection is employed, the preliminary steps of heating the body and the injection must of course be dispensed with. If the veins are to be injected, they should be washed out by an injection of pure ether.

3. Injection by Double Decomposition. — This method consists in taking advantage of the known power of certain substances to decompose each other, and form an insoluble compound. Upon the original method of using these materials, Henry Goadby, Esq. (late dissector of Minute Anatomy to the Royal College of Surgeons, London,) has made some important improvements, an account of which he first published in the London Lancet, and which has been republished in the Philadelphia Examiner for March, 1850. Mr. Goadby thus describes the original process and his own experience:

"M. Gruby has published an account in the Comptes Rendus of some very successful injections which he had made by employing certain fluids, which he used separately, and which, when they met, mutually decomposed each other, and deposited the colouring matter in the vessels themselves.

"He used saturated solutions of the chromate or bi-chromate of potash, and of the acetate of lead: he directed that equal quantities of these fluids should be used, first injecting all the chromate of potash, to the extent of one-half the quantity of injection supposed to be necessary, into the vessels, and subsequently the same quantity of the acetate of lead.

"As soon as these fluids meet, they decompose each other; the acetic acid of the acetate of lead combining with the potash to form the acetate of potash, which is set free, and the chromic acid of the chromate of potash combining with the lead to form the beautiful chromate of lead, which is deposited in the vessels.

" The reports which had reached me were highly confirmatory of M. Gruby's success with these fluids, and having seen Mr. Bowman's preparations of the kidney injected on this principle, and with the like materials, I determined to employ them. My experiments, however, were most unsatisfactory; for, having injected a terrier puppy, a dissection of several hours was required to ascertain whether I had succeeded in injecting any part or not, and my best reward consisted in a patch of capillaries, slightly painted of a pale yellow colour, and entirely wanting that roundness and fullness, characteristic of a good injection.

"I next procured a human foetus, and injected it, with precisely the same results.

"On making inquiry of Mr. Bowman, touching the ordinary success which had attended his experiments, and the experiments of others, so far as he knew, he told me that I appeared to have met with fair average results ; for that the labour of dissecting, consequent on using these fluids, was always great, and that the operator must consider himself well rewarded for two or three days' work, by finding a microscopic bit well injected.

"From this narration of failures, it will be evident that the fluids rarely meet in the


INJECTING MATERIALS. 45

vessels, otherwise the colour would be necessarily precipitated. With a view to see exactly what took place, I determined to inject a piece of intestine, in which the whole process would be under my inspection. I placed pipes in the mesenteric veins, and secured all the cut vessels in the usual manner ; I then proceeded to throw in the chromate of potash, and found that the potash would not wait for the lead, but came out instantly through the parietes of the vessels as fast as it went in, and in one broad stream covered the table. I repeated this experiment a number of times, but with the same uniform result; on some occasions I threw in the lead also, and as the vessels were moist with the chromate, the slight painting I have mentioned took place; but as only equal quantities of the two fluids produce the best colour, the excess of the lead was useless.

"Having observed, at this stage of my experiments, that the precipitated chromate of lead is remarkably fine and soft, I determined to use it, in lieu of vermilion, with size; and although the success was far greater than when I used the fluids separately, the results were in no way superior to the old red injection.

"The principle involved in M. Gruby's use of these fluids — that, namely, of forming the colour within the vessels themselves — appeared to be undeniably good, notwithstanding it had so signally failed in my hands, and, as far as I could learn, in the hands of all those persons who had hitherto employed it ; and I had no doubt that if I could succeed in giving some consistence to the fluids, the results might prove more satisfactory. For this purpose, size would not do, as it is rarely, when bought, much too strong for use, and it would not bear further dilution. I therefore procured the highly concentrated preparation employed by pastry cooks, and sold by by grocers, under the name of gelatine. The following is my formula for the double injection with this material:

"Sat. solution of bi-chromate of potash, eight fluid ounces; water, eight ounces; gelatine, two ounces.

"Sat. solution of acetate of lead, eight fluid ounces; water, eight ounces ; gelatine, two ounces.

"Thus, gelatine, two ounces, are dissolved in sixteen ounces of fluid, and kept and used separately as before; but the success consequent on the addition of the gelatine was quite extraordinary; the vessels were all full and round, and there was no extravasation; and for reasons hereafter to be explained, the microscope revealed scenes so rich in depth, colour, and beauty, as to exceed the - best red injections I have ever seen.

"With this form of injection I have never failed; I have injected three foetal subjects so minutely, that the capillaries of the skin, and of every tissue, were perfectly injected. Among the best specimens I obtained, I may mention injections of the papilla? of the lips, gums, and tongue; of the pulps and capsules of the teeth; of the conjunctiva and other tissues of the eye; of the mucous membrane of the nose and cellular tissue; fascia; periosteum, &c; ceruminous glands, lymphatic glands, and thyroid glands; pericardium, auricles of the heart, vasa vasorum, particularly of the aorta and vena cava, and the vessels of all the nerve sheaths. In line, one foetus occupied me in dissecting, ten hours a day, for two months, and was scarcely half finished at the expiration of the time.

"Having described the success attending the use of these injecting fluids, I must


46 INTRODUCTION.

new say how they are to be mixed and used, as every thing depends on care in these respects.

"Each parcel of gelatine must be dissolved in the water only, (eight ounces,) and in a separate water-bath. The water-baths I employ consist of two earthern pans, such as are applied to a child's chair, and capable of containing about one quart each; these are fitted to two tin kettles, the broad flange of the earthern pan resting on the rim of the kettle, the pan covered with a common saucepan-lid. The kettles should be furnished with a bail of iron wire, like that of a glue-pot, or pitch-kettle.

"The gelatine is to be slowly dissolved in the eight ounces of water; when this is accomplished, the eight fluid ounces of bi-chromate are to be added to the gelatine in one pan, and the eight fluid ounces of acetate of lead to the gelatine in the other ; each should be we'l mixed by stirring with a glass rod, a separate rod being used for each solution, lest the chromate of lead should be precipitated.

"The fluids thus prepared, must then be strained through fine flannel (using a piece for each fluid) into other vessels, the earthen pans cleaned, and the fluids returned to them. The injections are now ready for use, and must be kept at a temperature of about 90° by the warm water contained in the kettles.

"Directions for using the Injection. — The best subject to inject is a foetus, as there are no cut vessels by which the injection can escape. A pipe, with a stop-cock attached, should be firmly tied in the umbilical vein, leaving the arteries open until the yellow injection makes its appearance, when they should be secured. It is most essential that, for this injection, the subject be warmed through by immersion in warm water, the temperature of which must not be higher than 90°, or corrugation of the tissues will take place ; it will require from one hour to two hours to accomplish this, and the temperature must be maintained until the injection be completed. The whole sixteen ounces of the potash preparation of gelatine must now be used, care being taken that its temperature never exceed 90°. Some manipulators deem care of little import in the early stage of injecting, and throw in the first few syringefulls rapidly, and only exhibit caution when the subject begins to fill. In my experience, this is an error; and he who would succeed, must be equally careful and patient throughout. It is my practice to let the piston descend so slowly, that it can scarcely be seen to move.

" Having used the whole of the first preparation, the acetate of lead must be used, when the colour will instantly be formed, and give the operator some idea of his progress.

"The temperature of the subject must be kept up, and a fresh batch of injection made and strained as before. In about half an hour the injection may be resumed, and the bi-chromate again claims precedence; but only half the quantity need be used now, followed by an equal quantity of the lead. At this point the stop-cock should be turned, and the subject again allowed to rest for half an hour; the remainder of the injections may then be used, and after this, in all probability, the subject will require another batch. The manipulator who employs, for the first time, as much injection for a foetus as I have already directed to be used, and who experiences the great resistance opposed to the transmission of the last several syringes-full, especially as the body will by this time be swollen and tense to an amazing degree, will feel somewhat surprised to learn, that if he suspend the operation for an hour, keeping up the temperature in the meanwhile, he will be able to throw into the subject twenty


INJECTING MATERIALS. 47

or thirty ounces more with comparative ease, and have the pleasure of seeing many isolated congeries of vessels of the skin gradually approaching each other, and finally anastomosing most perfectly, while the tension of the body will be so great, that if the piston be pressed completely down, and the hand withdrawn, it will gradually rise, and the same may, with care, be repeated several times, without causing extravasation.

"Towards the conclusion of the process, the injections should be thrown in alternately ; and this should be continued, notwithstanding the prodigious distortion of the body, as long as the injection is felt to flow in the vessels. To inject a foetus well, on this plan, will occupy from four to five hours. The operation finished, the body should be thrown into cold water, and should not be dissected until the next day.

" The Dissection, — Will soon reveal what has become of the injection, and is altogether a disagreeable and difficult task. It will be found that nearly all the gelatine and acetate of potash have transuded and separated the tissues widely from each other, and that the blood has been diluted, and intimately mixed with the gelatine, which is coloured by it.

"The majority of preparations thus injected, require to be dried, and mounted in Canada balsam. Each preparation, when placed on a slip of glass, will necessarily possess more or less of the coloured infiltrated gelatine, which, when dry, forms, together with the different shades of the chromate of lead, beautiful objects, possessing depth and richness of colour. The gelatine also separates and defines the different layers of vessels. By this injection, the arteries are always readily distinguishable, by the purity and brightness of the chromate of lead within them, while the veins are detected by the altered colour imparted by the blood.

"Those preparations which require to be kept wet, can be preserved perfectly in my B-fluid, specific gravity 1,100; the A-fluid destroys them.

"The bi-chromate of potash is greatly superior in colour to the chromate, which yields too pale a yellow; and subsequent experience has convinced me that the acetate of potash frequently effects its liberation by destruction of the capillaries, and this, even long after the preparations have been mounted in Canada balsam ; perhaps this may be owing to some chemical action of the acetate of potash upon them.

"Although highly desirable, as the demonstrator of the capillaries of 'normal tissues, I do not think this kind of injection fitted for morbid preparations, the infiltrated gelatine producing appearances of a puzzling kind, and calculated to mislead the pathologist.

"In preparing portions of dried, well-injected skin for examination by the microscope, I have tried the effect of dilute nitric acid, as a corroder, with very good results. But probably, liquor potassse would have answered this purpose better."

The writer has inspected many beautiful injections in the possession of Dr. Goadby, by his chemico-gelatinous method, and can confirm the foregoing account of his success and the excellence of his method.

Dr. Goadby, in the article referred to, recommended that the nitrate of lead be substituted for the acetate ; on experiment, however, this change has not been found to answer, as the colour after mounting has been observed to fade.

Other colours may also be obtained by the method of double decompo


48 INTRODUCTION.

sition ; thus, a red precipitate, by the iodide of potassium and the bi-chloride of mercury ; blue, by the ferro-cyanide of potassium and the peroxide of iron, &c.

Most of the preceding remarks apply — 1st, to cases in which the whole or large part of the subject is to be injected ; and, 2d, to cases in which both arteries and veins are to be injected by one material.

The perfect injection of only one set of vessels or the two sets by different materials, so as to fill the capillaries, and yet not exceed each one's proper limits, is one of the most difficult operations in minute anatomy : it is comparatively easy to fill both orders of vessels by one injection.

With regard to the amount of force, and quantity of fluid necessary for the injection of only one set of vessels, no directions can be given that would not require modification according to each particular case ; and success must depend more on repeated trials than upon any rules.

In cases where two or more materials are to be injected, the arteries, on account of their lesser volume, should be first filled. The colours may be used in the following order: Arteries, blue; Veins, yellow.

When red and yellow are used, the two colours meeting in the capillaries, form an orange tint, making it difficult to recognise each proper colour.

When the liver is to be injected, its four orders of vessels may be thus filled : Arteries, blue ; Vena Portse, yellow ; Hepatic vein, red ; Hepatic duct, white.

When the uriniferous tubes are to be filled, they may be injected with white.

A few other materials for fine injections may be here noticed, although the best have been already given :

Pure Gelatine. — In using this material, Tulk and Henfrey direct that seven parts in winter and twelve parts in summer of dried gelatine be dissolved to the consistence of jelly in one hundred' parts of water. The jelly is then to be made liquid, as flowing as water, by gentle heat, and the colouring matter added. The colouring particles must be suspended in water : a red colour may be produced by vermilion or carmine ; blue, by indigo or Prussian blue ; yellow, by gamboge, &c.

After the injection has been strained through a fine cloth, it is ready for use, and must be thrown in while warm. This gelatine is the same employed by Dr. Goad by in his method by double decomposition, and ma) r be procured at the druggist's or grocery stores.

Fresh milk, used before the cream has commenced to form, and coloured by a watery suspension of the finest particles of indigo, carmine, &c, may also be used. When the injection is completed, the preparation must be deposited in acetic acid, or dilute hydro-chloric acid, for twelve hours to coagulate the milk.


PRESERVATION OF OBJECTS. 49

This form of injection is said to be well adapted for organs that have been preserved for any time in weak alcohol. In this fluid, the vessels become so contracted, that any thing like minute injection is very uncertain.

The ingredients employed by Berres and Hyrtl, of Vienna, whose injections have become so famous, are finely levigated cinnabar, copal varnish, and gum mastich. For a full account of Berres' method, see his " Microscopic Anatomy," fob, published at Vienna, in Dutch and Latin, 1837.

In conclusion, the writer would state that, from personal experience and observation, any of the foregoing methods may prove perfectly efficient and satisfactory, if proper time be allowed to make the injection, due attention paid to the preliminaries, and sufficient perseverance exercised to obtain any useful experience.

The anatomist will therefore find it to his interest to persevere in any particular form of injection he may select, rather than make occasional trials with different materials.

In addition to these requisites, success, in any given case, will be found to depend much on the peculiar condition of the vessels, a certain willingness on their part (if it may be so expressed) to be injected. This condition will be more generally found in animals that have been bled to death.


III.— PRESERVATION OF OBJECTS.

To properly preserve objects that have cost much time and labour to prepare, will be at once acknowledged a most important part of microscopical manipulation. The different cements useful to the microscopist will be first described. Not to embarrass the beginner with too long a list, the most useful only are given.

CEMENTS.

1. Jaf annex's Gold-size. — This mixture may be obtained at almost all the varnish stores, and consists of boiled linseed oil, dry red-lead, litharge, copperas, gum-animi, and turpentine. Its cost is trifling, but it needs to be about three years old before it will dry rapidly. It should have the consistence of thick syrup, so as not to run too much when applied. If the goldsize be too thin, it may be thickened by being rubbed up with a little lampblack or litharge. This cement is the most useful of all for fastening the covers of cells, and may also be employed for cementing the cells themselves to the glass slides.

2. Asphaltum Cement. — This is made by dissolving asphaltum in boiling linseed oil or turpentine, and is of fine jet-black colour. It may be used for cementing cells to slides, or cementing down the covers of the cells. It is

4


50 INTRODUCTION.

not acted on by weak alcoholic solutions, and may therefore be used when alcohol is employed as the mounting fluid : as a cement for the covers of cells, it is by no means equal to the gold -size.

3. Sealing-wax Cement. — This is prepared by dissolving a quantity of any coloured sealing-wax in alcohol, sufficient to produce a cement of the consistence of thick syrup. Its uses are the same as the two preceding cements, but inferior to both.

4. Canada Balsam, dissolved in ether or turpentine, and evaporated to a consistence sufficient to allow its being laid on with a camel's-hair brush, has been recommended as a cement for fastening cells to the glass slides. Tt needs, however, the addition of a little heat, to render it sufficiently fluid to make the union firm, and free from air bubbles. This heat may be applied by means, of a spirit-lamp to the under side of the glass slide, after the balsam has been put on, and the cell placed in the desired position. When the balsam becomes fluid, the cell may be pressed down, and the air bubbles will escape. This cement is apt to become brittle by age.

5. Marine Glue. — This substance is in most use abroad for cementing cells to glass slides, and is composed of gum-shellac, caoutchouc, and naptha. The kind best adapted for microscopic purposes, is that known in commerce, as G. K. 4, and may be procured from Messrs. Pike and Sons, opticians, of New York, at a small expense.

The directions given by Mr. Quekett, and others, for its use, involve a long and tedious process, and are here omitted. A method equally good, and consuming much less time, has been adopted by the writer, and is in every way satisfactory : A small tin cup, with a cover, is used, capable of holding about six ounces ; into this is poured about two ounces of Canada balsam, and about the same quantity in bulk of the marine glue, cut in shavings. These are placed over a spirit-lamp, or in a sand bath, and stirred occasionally, until they begin to boil, when the cement is ready for use. It is then applied with a brush to the under side of the cell to be cemented on, and pressed on the glass slide, previously warmed. By this method, twenty-five or thirty cells may be cemented in a very few minutes, and the cement may be put aside, and will be again ready for use on being heated to fluidity.

6. Compound Cement. — This mixture, which the writer has found the most useful and least troublesome of all cements, is made — first, of gum-shellac dissolved in naptha, and of the consistence of syrup; this cement — as it dries very quickly and is quite hard and firm — would be very useful by




PRESERVATION OF OBJECTS. 51

itself, were it not for its brittleness; this is obviated by mixing it with equal parts of thick gold-size. This cement, which must be kept in a stoppered bottle, is always ready for use, and may be applied without heat, by means of a camel's-hair pencil, to the under side of the glass cell. This is pressed firmly on the glass slide, and the superfluous cement may be scraped off, when hardened. This cement dries rapidly, is not brittle, is not acted on by any of the fluids commonly used for mounting objects, and has the great advantage of being always ready. It may also be used for fastening the covers of cells where a thick cement is needed. But for this purpose nothing can be better than the gold-size, three or four years old.

7. Gum- Arabic Cement. — A very strong cement may be made by dissolving three parts gum-arabic and one part of fine sugar in distilled vinegar.

The cement sold in the shops as the diamond cement, which depends for its adhesiveness on the isinglass contained in it, and also the liquid glue, which contains a large portion of gum-shellac, may be made use of as occasion requires. The best cements, however, are the first, fifth, and sixth of those already mentioned.

Glass Slides and Cells for preserving Objects. — The glass slide, so useful in microscopic examinations, and so necessary in the preservation of objects, is a plain slip of thin plate or flattened crown-glass, three inches long and one inch wide. The size is of course arbitrary, but the one mentioned is that recommended by the London Microscopic Society, and is in general use by English and American microscopists : it is therefore desirable that in exchanges and purchases, a uniformity of size should exist. The plate or crown-glass is purchased in sheets; the former being much the best, but most expensive, and is first cut with a glazier's diamond in slips three inches wide; these are again cut in slips one inch in width, which gives the necessary size: the rough edges are made smooth by rubbing them on a cast-iron plate, with emery-powder wet with water. It is much better, however, to have this done at a lapidary's or glass-cutter's; Mr. Isaac Taylor, glass-cutter, corner of Hester and Elizabeth streets, New York, will smooth any number of slides at the rate of fifty cents per one hundred.

Thin Glass. — The thin glass used for covering certain objects, fluids, &c, while under examination with the microscope, and for forming the covers of cells that are destined to preserve objects, is manufactured by Messrs. Chance and Company, of Birmingham, solely for this purpose. It is of two varieties of thickness, and known as thick and thin glass : in each case it is sold by the ounce, the thin glass costing about twice as much as the other,


52


INTRODUCTION


but of course containing more in surface. Messrs. Chance and Company have a branch of their house in New York, at No. 42 Cliff-street, and are so obliging as to sell any quantity, however small, at much more moderate rates than were formerly demanded by opticians and others, who imported it themselves. The plate and crown-glass for slides may also be procured at the same house.

For use, the thin glass is cut in squares, about three-quarters of an inch in size, or in circles, a little less in size than the outer circumference of the cell to be covered. In either case, the cutting is performed by a writing diamond, the glazier's diamond being too heavy. To cut the thin glass in squares is very easy, care being taken that the sheet of glass to be cut is made to lie flat on a hard smooth table, or, still better, on a sheet of plate glass slightly wet. To cut circular covers from thin glass, is rather more difficult : it may be done by taking a thin section of glass tube, or a circular piece of stout gutta-percha, of the size desired for the covers, and laying it on the thin glass (this having been previously cut in strips), and then passing the diamond either inside or outside of the circle, according to the size desired.

For those who prefer this method of cutting circular covers, a most useful instrument has been devised by Mr. Wm. E. Johnson, of Utica, consisting of a stout piece of German silver or other hard metal, about eight inches long, one and a half wide, and one-eighth of an inch thick. In this plate are drilled circles of different sizes, from T 9 g to |f of an inch in diameter. The circular covers of thin glass can, by aid of this instrument, be cut of any required size, and the weight of the metal makes the instrument less liable to slip, than when a section of tube or gutta-percha is used. The form of the instrument is represented at Fig. 6 :



To cut glass satisfactorily by this method, it is necessary to use a diamond having a true point, or one that will cut in any direction. Most of the writing diamonds sold, will cut but in one direction.

Mr. Quekett has described an instrument devised for the purpose of cutting thin circular covers. A much simpler instrument, however, is represented in Fig. 7 :


PRESERVATION OF OBJECTS.


53



Fig. 7.

It usually forms one of the instruments furnished in a mathematical instrument case, and can be readily procured at any store where such instruments are sold : It consists of two arms united by a cradle joint ; one arm pointed, like the arm of a pair of ordinary dividers. The other arm is about onehalf the length, having a circular opening, divided perpendicularly in the centre. The two sides of this circle are made to approach and separate by means of a small adjusting-screw. The original design of the instrument, is to draw circles on paper, by means of a lead pencil fastened in the circular opening by the screw. In cutting glass, the writing diamond is substituted for the lead pencil, and after the cutting-point of the diamond is turned in the proper direction, the diamond-holder is to be secured at the proper distance by means of the screw: as the steel arm of the instrument usually terminates in a sharp point, this must be removed, and a blunt point made. This may rest on a small circle of flat lead or box-wood, or gutta-percha. If it be found this rest is disposed to slip, a piece of chamois leather may be pasted on the under side of the rest ; if necessary, this may be moistened with a little water or a thin mucilage of gum-arabic.

The instrument having been adjusted so as to cut a circle of the required size, is firmly held upon the thin glass, this having previously been cut in slips a little larger than the required circles, and made to describe a circle


54 INTRODUCTION.

in the same manner as if the lead pencil and paper were used. Sometimes it will be found better to turn the slip of glass round, holding the diamond stationary. The pressure must be light, but steady, and the edges outside the circle are easily removed. ,

Glass Cells. — For the preservation of injected preparations and other thick animal structures, some kind of cell is necessary in which to deposit the object. This cell may be made of glass, of gutta-percha, or some thick cement, painted on the slide in the desired shape, and allowed to harden. Those of glass are the best, and are of different kinds.

1. The Thin-glass Cell. — This cell, useful in mounting thin and delicate structures, is made by taking a square inch of the thicker kind of thin glass, and drilling a hole in it of about half an inch in diameter. The glass so drilled is then to be cemented to a plain glass slide, by means of the marine glue, or the compound cement, in the manner already described. When the cement becomes dry and hard, the cell, after being properly cleaned, which may be done by scraping off the harder portions of the cement with a knife, and then washing the cell with a solution of borax, or some sulphuric ether, is ready for use.

2. The Drilled Cell, is made in the same way, but in this form, plate-glass of any desired thickness may be employed, according to the thickness of the object to be mounted. Hence, if this form of cell be used, it will be necessary to have them of different degrees of thickness, as well as of different sized calibres. They are to be cemented to the glass slides in the same manner as thin glass cells. When these cells are well made, they are the best in use; but, as will readily be seen, it is a difficult matter to drill the holes without fracturing the glass.

3. Tube Cells. — These are sections of stout glass tube, of different calibres, from ith to |ths of an inch, cut of any desired thickness, and cemented to the glass slide in the same manner. These sections are readily made by means of a lapidary's wheel, charged with diamond-dust; afterwards the cut surfaces must be ground perfectly flat, but not polished. These cells are exceedingly neat in appearance, and can be obtained at much less cost than the drilled cells. Mr. Mason, lapidary, No. 156 Fulton-street, has made many of these cells for different microscopists in this city, and at much less price than it would cost to import them. Where only one size can be obtained, a cell of about f ths of an inch in calibre, and ith of an inch in thickness and height when cemented, will be more generally useful than any


PRESERVATION OF OBJECTS. 55

other one size. It is better to have them of different sizes, where this is possible.

4. Built-up Cells. — When neither of the preceding forms of cells can be obtained, the built-up cells will be found a good substitute, and can be easily made by the student himself. These consist of four pieces of glass of proper thickness and width, cemented to a glass slide, so as to form an oblong or square cell. Take, for instance, a piece of plate-glass, |th of an inch in thickness, one inch in length, and f ths of an inch in breadth ; then with a glazier's diamond and rule, cut off strips from each side, ith of an inch in width, and cement these to the plain glass slide, in the precise order in which they were cut off. This latter step in the process may be insured by marking the different corners with ink or the point of a diamond. These cells may be made of any size and thickness, and in these, as well as in the other forms of cells, the marine glue or the compound cement may be used.

5. Gutfa-Percha Cells. — Another very serviceable kind of cell, which may be employed when the drilled or tube cells cannot be obtained, is made from gutta-percha. Dr. Goddard, of Philadelphia, was the first to adopt this form, which is readily made in the following manner : Take a flat piece of gutta-percha of about |th of an inch in thickness, and with a saddler's-punch, f ths of an inch in diameter, cut several circles from the gutta-percha : then with a punch one size smaller, or about fths of an inch in diameter, cut from these circles a centre piece. This is to be thrown aside, and there remains a cell, resembling a glass tube cell, ith of an inch in depth, and with the sides -i-th of an inch thick : this is then cemented with the marine glue and Canada balsam to the plain glass slide, in the same manner as the other forms. Other cells may be made of white lead, melted marine glue, or gold-size thickened with lamp-black. These substances are all to be traced on the glass slide when in a fluid state, so as to form the necessary sized cells, and allowed to harden before fit for use. The superfluous material may be cut away before mounting the object.

Gutta-percha dissolved in chloroform, on account of its quickly-drying properties, has been recommended for this variety of cell. The writer has used it, but does not find it possesses any advantages over the other substances already named, and indeed is not equal to the cell made with gold-size and lamp-black.

In constructing cells of either of these materials, it has always been found difficult to draw the cell so true in form, as to have a neat appearance. The writer has adopted a method by which circular cells may always be described exactly true, and made of any desired depth. For this purpose,


56 INTRODUCTION.

the little instrument with the writing diamond used in cutting circles of thin glass, is employed.

In the present operation, a camel's-hair pencil, fine or coarse, according to the desired thickness of the cell, is substituted for the writing diamond : the pencil, having been dipped either in the asphaltum, gold-size, or anyother cement, is made to describe a circle in the same manner as the diamond in cutting the thin glass. Smaller cells, constructed in this way, will be found very useful in mounting minute portions of muscular fibre and other delicate structures that require to be viewed with high powers.

FLUIDS FOE MOUNTING OBJECTS,

These require to be varied according to the nature of the structure to be mounted : among many that may be used for this purpose, the following are the most useful :

It may be here remarked that all the fluids that may be employed in mounting objects, should be prepared sometime before required for use; otherwise many of them will be found to contain an infinite number of airbubbles, which will require the object to be remounted before it can be studied with the microscope.

1. Alcohol and Water. — As in the preservation of large specimens of general anatomy, alcohol and water is more generally useful than any other fluid, so by the microscopist, this mixture is more to be relied on than any other. The proportions used in ordinary preparations (equal parts of water and alcohol) will be found too strong for most of the cements used in microscopic manipulation ; and it has been ascertained that a weaker solution than the above will answer perfectly well as a preservative, and not act on the cement. The proportion best adapted for this purpose, is one part alcohol, about 60° above proof, to five of distilled water : with this fluid, the gold-size, or asphaltum, may be safely used in cementing down the covers of cells.

2. Goadoy's Solution. — The following formulse are those in use by Dr. Goadby, for the second of which he was rewarded by the " Society of Arts," with a gold medal.

A-l Solution. — Rock salt, 4 ounces; alum, 2 ounces; corrosive sublimate, 2 grains ; water, 1 quart. Mix. Very astringent.

A-2 Solution. — Rock salt, 4 ounces; alum, 2 ounces; corrosive sublimate, 4 grains ; water, 2 quarts. Mix. Generally useful, except where the carbonate of lime is present.

B Solution. — Rock salt, 8 ounces ; corrosive sublimate, 2 grains ; water,


FLUIDS FOR MOUNTING OBJECTS. 57

1 quart. Mix. Specific gravity, 1.100. — Two ounces of salt in addition to each quart of water will make the specific gravity 1.148.

This solution preserves the transparency of all tissues, and is used for terrestrial and fresh-water animals. Marine animals require the specific gravity to be increased to 1.148 or even higher.

3. Acetate of Alumina. — The famous Gannal process, formerly so much in vogue in Europe, consists in using one part of acetate of alumina, with four of distilled water, either as an injection, when it is said it will prevent decomposition, or as a fluid for mounting objects. Its destruction of bone is an objection to its employment under certain circumstances.

4. Creosote. — This is an excellent preservative, but requires some care in its preparation with water. One of the best methods is to mix it with water, and then distil the mixture. The water will come highly charged with the creosote. The only objection to the employment of this fluid, is its tendency to turn the preparation brown. An excellent fluid, known as Mr. Thwaite's fluid, contains creosote as an ingredient, and is thus prepared : To sixteen parts of distilled water add one part of pure alcohol and a few drops of creosote : stir in a small quantity of prepared chalk, and then filter: with this fluid mix an equal quantity of camphor-water, and strain through a piece of fine linen.

5. Glycerine. — This fluid, now to be obtained at most o the drug-stores, forms with equal parts of water a valuable preservative for delicate tissues, in which it is important to preserve the bright colours. Hence, for the delicate colours of living infusoria, it will answer better than any other fluid. If the glycerine be used pure, its highly refracting properties will sometimes prevent the object from being well shown. To the glycerine, salt, corrosive sublimate, spirit of wine, or creosote, may be added, if desirable.

6. Canada Balsam. — This very useful material is employed when it is desired to increase the transparency of an object, as in sections of teeth, bone, &c, or in some instances, to mount injectings that have become dried. It may be used with heat or without, and directions will be subsequently given for its use in both methods.

7. Salt and Water. — A solution, containing five grains of common salt to one ounce of distilled water, will preserve many animal and vegetable preparations. Mr. Quekett mentions that the common objection to all saline preservatives, viz: the growth of conferval in them, may be obviated by


58 INTRODUCTION.

the addition of a few drops of creosote or camphor mixture. This, however, is inferior to Goadby's B-solution.

8. Naptha. — In the proportion of one part of naptha to seven or eight of water, a good preservative is obtained for ordinary objects. It is stated that this mixture is now generally used abroad by Messrs. Hett, Topping, and others, as the best preservative of injected preparations. If this be true, it is a strong recommendation in favour of its employment.

Dr. Hannover, in Muller's "Archives," 1840, recommends the employment of a solution of chromic acid as a preservative fluid, and also, as a fluid in which soft tissues may be hardened for future dissection. In a weak state, as one part to twenty of water, pus, mucus, epithelium, blood corpuscles, and other delicate structures, are well preserved : when the solution is too strong, the tissues acquire a yellow or even red colour.

The writer has not used this solution as a preservative sufficiently long to test its merits, but can speak well of its hardening properties : brain, liver, and other soft tissues, after being deposited in this solution a short time, acquire a degree of hardness sufficient to allow of very thin sections.

The following excellent general directions for mounting objects, are given by Mr. Quekett, in his work already so often quoted : " For all large specimens, such as injections, the spirit and water, or Goadby's first solution, may be used; and for others, either the creosote or glycerine solutions, as those containing saline matter, when placed either between glasses simply, or in the thin glass cells, are apt to crystallize slowly, and interfere with the objects that are mounted in them. Goadby's solution, containing both salt, alum, and corrosive sublimate, will keep animal structures that have been injected with size and vermilion, exceedingly well ; but those in which the vessels are filled with flake-white will have that substance destroyed in a few hours; in these cases, either the arsenical or the spirit and water only should be employed. The glycerine fluid, when kept for some time, is apt to become mouldy, it should, therefore, be mixed in small quantities, and then only a few hours before it is required. When objects are to be mounted in either of the above fluids, it must be laid down as a rule, that they should have been soaking for some hours in the same fluid, or in a fluid of a similar kind ; this should be more particularly attended to, when the preparation has to undergo dissection in water, previous to its being mounted. It has often happened to the author to find a preparation that had been dissected in water, and mounted in a cell in spirit and water immediately after, completely covered over with small air-bubbles in a few hours, from the slow admixture of the two fluids. With Goadby's solution, it does not so often happen ; but with this, a white sediment will be sometimes deposited in the bottom of the


FLUIDS FOR MOUNTING OBJECTS. 59

cell when the preparation has been soaking in spirit for some time previously."

Objects are usually mounted in one of four ways. These are — 1, the dry way; 2, in Canada balsam with heat; 3, in fluid; 4, as opaque objects.

l.-THE DRY WAY.

This method is adopted in mounting objects which show best their peculiar structure without the addition of fluid or Canada balsam. Such objects are some thin sections of bone and teeth, some kinds of hairs, some urinary deposits, &c. It may be stated here, however, that unless a particular method is known, from repeated trials, to be superior to all others, the different methods should be adopted with a view of trial, where the specimens are large enough to divide in this way. Now, although some sections of bone and teeth show better for being mounted in the dry way, yet some others show better in Canada balsam ; the choice depending in some degree on the thickness of the section, and the density of the structure. If the specimen to be mounted be a rare one, and the quantity small, it should be examined with the microscope before being permanently mounted. This may be easily done, both in the dry way and in fluid. Having determined to mount an object in the dry way, the first step is, to properly cleanse the specimen, as it will be always found, on examination, that, no matter how clean an object may appear to the eye, or even with a low power of the microscope, numerous particles of dust will be found on it.

These, if not removed, may not only prevent the true structure of the object from being determined, but by the beginner may be mistaken for part of the structure itself. Indeed, M. Robin recommends the microscopic study of dust-particles as a preliminary to the proper study of animal preparations.

Ordinary preparations may be cleansed by soaking them for a few hours, previous to mounting, in distilled water, or by washing them with a small syringe and water. Specimens that contain grease, as sections of bone, &c, may be cleansed by soaking them in sulphuric ether or spirits of turpentine. After being properly cleansed, the specimen must then be allowed to dry. If the object be a thin one, it is to be placed upon a plain glass slide, and covered with a square or circular piece of thin glass, a little larger than the object. The cover is then pressed firmly down, and fastened with thick gold-size, or with the compound cement, or the diamond cement, always being careful to paint on a thin coat of cement, at first, and a thicker one afterwards.

If the object be too thick to allow the cover to approach the slide, the intervening space may be filled up by small pieces of paper, card-board, or thin gutta-percha, having a hole punched out in the centre, a little larger


60 INTRODUCTION.

than the object. These are first to be cemented to the slide ; the object is then deposited in its place, and the cover cemented down as before.

If the specimen to be mounted be a section of lung, gland, intestine, &c, and some of these show their structure very well when mounted in the dry way, one of the different forms of cells before described, may be used. The depth of the cell being always proportioned to the thickness of the object, it being desirable to have the surface of the object as near the cover as possible, the more readily to receive the light. The cover is then to be applied and cemented with the gold-size.

2. -CANADA BALSAM WITH HEAT.

This method is adopted in mounting thin objects that require to be made more transparent than they are in the dry state, and at the same time such as will not be injured by heat. Sections of bone and teeth are often mounted in this way. The Canada balsam, or, as it is sometimes called, balsam of fir, used in this manipulation, should be rather old and thick, as it then requires less heat to harden it than when new and thin.

The best way of keeping it for use, is a tall vial with a narrow mouth. From this vial the balsam may be dropped on the plain slide or object, and will be found a better plan of proceeding than that usually recommended, viz: of keeping the balsam in a wide-rnouthed jar, and taking the desired quantity by means of a glass rod. In this latter method, it will not only be found difficult to obtain the sufficiently small quantity required, but the portion taken will contain a much greater quantity of air-bubbles than when the balsam is dropped from the vial. The vial should be only about halffull, and allowed to stand uncorked for a day or so, in order that the airbubbles, may rise to the surface, and burst. ,

The object having been properly cleansed and dried, as directed in mounting objects in the dry way, it is to be deposited in the centre of the glass slide, and a sufficient quantity of balsam to be dropped on it to completely cover it. For most objects, one small drop will answer. The slide is then to be seized by means of an ordinary wire forceps with flat blades (covered with leather, if desired), and held over the flame of a spirit-lamp; care being taken to approach the flame gradually; otherwise the slide, if not broken, will have an infinite number of fine cracks in it, which will effectually spoil its further use. The slide is to be held over the flame at short intervals until all traces of air-bubbles are removed, care at the same time being taken to prevent the boiling of the balsam.

When there is no longer any appearance of air-bubbles, the slide is to be removed from the flame, and a square or circular piece of thin glass, previously cleansed and ready, is to be gently warmed, not heated, and pressed upon the object. The superfluous balsam will escape beyond the thin glass,


CANADA BALSAM. 61

and when cold may be removed with a knife, and subsequently perfectly cleansed by means of a rag dipped in ether. A modification of this plan of mounting is, to place the slide containing the balsam upon a piece of tin kept for the purpose, about four inches square, with the edges bent up, to prevent the glass from slipping off (a cover to the ordinary seidlitz-powder box will answer very well), and to hold this over the flame of the lamp by means of the wire forceps. In this plan, there is less danger of cracking the glass, but no other advantage.

Still another method is, to have a small table made of tin, supported by wire legs, sufficiently high to admit the spirit-lamp under it. The slide is then placed on the table, and heated to the necessary point as before. A little experience will enable one to judge how much heat is necessary to sufficiently harden the balsam and dispel the air-bubbles.

Objects may be mounted in Canada Balsam without heat, by dropping the balsam on the preparation, as before, and allowing it to remain uncovered for a day or two. In this time, the air-bubbles will usually burst, or will rise to the surface, where they may be broken by means of a needle-point. When there are no longer traces of air in the balsam, which may at any time be discovered by placing the slide under the microscope, and examining it with a low power, the thin glass is to be warmed, and pressed upon the object, when the superfluous balsam will escape. The preparation is to be set aside, and allowed to harden by drying before the escaped balsam can be removed. This method of course requires a much longer time, before the object can be properly finished, than when heat is employed, and is only adapted to cases where heat would injure the object.

When injected specimens are to be mounted in balsam, they should be placed in cells ; one of these of proportionate size and depth having been selected, and cleaned by means of ether, or a solution of borax and water, the object is to be deposited in the cell, and the unoccupied space filled with the balsam dropped from the vial. The balsam should not overrun the cell, but rise a little above the level of its edge. The slide is to be set aside for a day, where it will be free from dust, in order that the air-bubbles may rise to the surface, and burst. When there is no longer any trace of air in the balsam, a square or circular cover of thin glass, properly cleaned, and a little smaller than the outer circumference of the cell, is to be slightly warmed in the flame of a spirit-lamp, and placed over the cell. If the cover does not touch the cell at every point, gentle pressure is to be employed until the superfluous balsam is pressed out.

A sharp-pointed knife may then be used to remove the balsam outside the cell, when a thin coat of the gold-size is to be applied around the edges of the thin glass, so as to cement it to the cell. In a few hours or a day,


62 INTRODUCTION.

another and thicker coat of the size is to be applied, or a coat of the asphaltum or sealing-wax cement.

Should a bubble of air enter the cell during the operation of adjusting the cover or removing the balsam around its edges, the cover must be slipped half way off the cell, and another drop of the balsam added.

When the last coat of cement is quite dry, any trace of balsam may be removed from the slide or cover by means of a linen rag or old cambric handkerchief, dipped in ether, care being taken not to touch the cement, as all these are acted on more or less by the ether.

3.-0 EJECTS MOUNTED IN FLUID.

Objects mounted in fluid are usually preserved in some of the different forms of cells already described ; but some very delicate structures — such as muscular fibre, fibres of the crystalline lens, &c. — requiring high powers for examination, should be mounted as fiat (as it is termed) as possible. With preparations of this order, the following method may be adopted : A clean plain glass slide having been selected, the object is to be deposited in the centre: if there are several specimens of the same objects, as several fibres of muscle, they should be slightly separated by means of a needlepoint. A drop or two of the mounting-fluid is then to be added by means of a pipette, when the thin glass cover, square or round, is to be placed gently on the fluid. If the object has escaped to the edge of the thin glass, it will be much easier to remove the cover, and begin again, than attempt to push back the specimen with a needle. A very good method to secure the object in any desired position, is to moisten it with a little water, or spirit and water, and allow this to evaporate, when the object will adhere to the surface of the glass. The fluid that escapes beyond the edges of the thin glass may be removed by means of a camel's-hair pencil, when a very thin coating of the gold-size is to he applied around the edges of the cover. When this is dry, another, and sometimes a third coat, must be added in the same way. When quite dry and hard, the whole slide may be cleaned with a solution of borax and water. This solution is at once cheap, very cleansing, and should be always at hand.

The thin glass cell, or the cell made with any of the cements, or the white-lead, &c, as previously described, may be also used for mounting this description of objects. When the thjn glass cell can be obtained, this will be found preferable to all others.

Portions of injected preparations — such as sections of kidneys, liver, intestines, &c. — of different degrees of thickness, require mounting in cells of proportionate depth. The method is nearly the same as in mounting in cells with Canada balsam. The object being placed in the cell, the fluid is to be added either from a vial or by means of a dropping-tube, so as to fill


OPAQUE OBJECTS. 63

the cell completely full without overrunning it. The cover is then to be gently dropped upon the cell, and the escaped fluid must be carefully absorbed by means of thin bibulous paper, or, still better, by a camePs-hair pencil. If a bubble of air has entered the cell, the cover is to be half drawn off, and more fluid added ; a thin coat of cement is then to be applied, and the object finished, as already directed.

4. -OPAQUE OBJECTS. It has been found that some objects, although sufficiently transparent to allow the light to pass through them, yet show their structure better when viewed upon a dark ground, or, as it is termed, viewed as opaque objects. Any transparent object may be made opaque, by turning away the mirror from the stage of the microscope, or by interposing a dark stop between the object and the mirror. Both these methods, however, may be troublesome at times, and objects that require a permanent dark ground may be mounted opaque by placing a small circle of black paper or blackened silk (court plaster will answer very well) beneath the object, if it be mounted dry ; or, if mounted in balsam or fluid, either the paper or silk may be pasted on the under side of the slide. The object should be covered with thin glass, as in other methods of mounting, to prevent injury from dust.

Labelling Slides. — The best method of labelling slides, is to write the name of the object, and the particular point it is intended to exhibit, on the right-hand side of the slide, with a writing diamond, such as is used in cutting the thin glass. On the left-hand side of the object may be written the date of the mounting, the style of the mounting, whether dry or in balsam, or the name of the fluid used. This will be readily seen to be desirable information, as when several hundred objects are collected together, it is impossible to remember the peculiarities of each without some memorandum. The advantages of each different mounting may be thus compared when several specimens of the same object are mounted in different styles, and this experience may be a guide in future preparations.

Some prefer to cover the slides with paper, either plain or ornamented, and write the contents of the slide with ink. In pursuing this method, a circle is cut from the centre of the paper by means of a saddler's-punch a little larger than the object; the paper is then pasted on by means of the gum-arabic cement, and the edges turned down over the edge of the slide; another similar piece of paper is pasted on the opposite side of the slide, and neatly trimmed off. In this method, there is usually less danger of breaking the thin glass cover in subsequent handling, but it will be found to consume considerable time, and, unless very well done, does not make so


64 INTRODUCTION.

neat an appearance as the first method : farther, it cannot be well employed when any form of deep cell is used.

Cabinets. — For the purpose of preserving microscopical objects free from dust and from danger of breakage, cabinets of different construction are employed. Where economy in room is not consulted, those made with shallow drawers, having a depth of about half an inch, will be found the most convenient. In these the slides all lie on their flat surfaces, where any particular one may be more readily reached than when they are placed on their edges. There is also in the former method less danger of the cells leaking or their covers being broken.

A favourite method with some, and one occupying much less room, is the employment of drawers one inch deep, in which racks are placed at proper distances to receive the slides on their edges. This is the most compact sort of cabinet, and two or three thousand slides may be thus preserved in a very small space. The objections to the plan are, the difficulty of readily finding any desired slide, as you only can see the edges of the glass, and not the object, and also the danger of breakage to the cells containing fluid. A method, combining safety and compactness, is the employment of boxes fitted with racks, and each box capable of containing two dozen slides placed on their edges. The boxes are then placed on their ends between permanent partitions in the cabinet; and when arranged and labelled according to subjects, any particular box or object may be readily reached, and all the slides while in the cabinet rest on the flat surfaces.

Still another method is, to have boxes made in the shape of books, and filled with racks, so as to contain two dozen objects. The cover of the box may be fastened by means of a clasp, and the boxes, when arranged in a book-case or on the mantel-piece, have a neat appearance. The objects are kept in the horizontal position, and being arranged in subjects, are very accessible.

In the preparation of the foregoing Introduction, valuable assistance has been derived from the following works, to which the student is referred for more complete accounts of some methods of Manipulation: "Quekett's Practical Treatise on the Microscope," "Anatomical Manipulation, by Tulk and Henfrey," and "Du Microscope and et des Injections, par Ch. Robin."


Part I. Fluids Of The Human Body

The constituents which enter into the formation of the body, and by the combination of which the human frame is built up, naturally resolve themselves into two orders, Fluids and Solids, the latter proceeding from the former.

In accordance with this natural division of the elements which enter into the composition of the body, it is intended to divide this work into two parts : the first of which will treat of those components of our frame-work which are first formed — the Fluids ; and the second will be devoted to the consideration of those constituents which proceed from the fluid elements, viz : the Solids.

Of the fluids themselves, it is difficult to determine upon any subdivision which shall be altogether without objection ; perhaps the most practicable and useful division of them which can be made is, into organized and unorganized.

To the above arrangement of the fluids the following exception might be taken : all the fluids in the animal economy, it may be said, are to be considered as organized, inasmuch as their elaboration is invariably the result of organization. But it is intended that the words organized and unorganized, when applied to the fluids in this work, should have a very different, as well as a more precise signification, and that those fluids only should be called organized which contain in them, as essential, or, at all events, as constant constituents, certain solid and organized particles ; while those liquids which are compounded of no such solid matters, as essential portions of them, should be termed unorganized.

In the first category, the lymph, chyle, blood, mucus, as normal, and pus, as an abnormal fluid, would find their places together with the milk and semen. The fluids of this class, it will be seen, belong especially to nutrition and reproduction, and admit also, naturally, of arrangement into two series: in the first, those fluids which are concerned in the nutrition and growth of the species itself would be comprised — as lymph, chyle, and blood ; and in the second, those liquids which appertain to the reproduction, nutrition and growth of the new species, as the milk and semen, would be admitted.

In the second category, viz : that of unorganized fluids, the perspirable Jluid. the saliva, the bile, and the urine, as well as probably the fluid of the pancreas, and of certain other glandular organs, would be found.

This arrangement of the fluids of the human body might be represented tabularly, thus :



FLUIDS.



ORGANIZED.




UNORGANIZED.


FIRST SERIES.




Perspirable fluid.


Normal :




Saliva.


Lymph.




Bile.


Chyle.




Urine.


Blood.




Pancreatic fluid (?)


Mucus.


&.C., &c, &c.


Abnormal :


Pus.


SECOND SERIES.


Milk.



Semen.


If the terms organized and unorganized be objected to, the words compound and simple might take their places, and would well express the distinction which characterizes the two series of fluids ; the former appellation being applied to those fluids which are compounded of both a solid and a fluid element, and the latter to those which do not possess this double constitution.


ORGANIZED FLUIDS.


ORGANIZED FLUIDS.

Article I. — The Lymph and the Chyle

It will perhaps render the description of the lymph and the chyle more intelligible, if the observations which we shall have to make on these fluids are preceded by a short sketch of the lymphatic system itself. This system consists of vessels and of glands, which are of the kind, which has been denominated conglobate. The vessels have many of the characters of veins, commencing as mere radicles, which unite with each other to form larger trunks, and their interior surface is provided with valves : they arise from all parts of the system, even the most remote ; those of the lower extremities and abdominal viscera form by their union the thoracic duct, which, running along the left side of the spinal column, unites with the left sub-clavian vein, near its junction with the internal carotid, its contents becoming mingled with the torrent of blood in that vein. The lymphatics of the left side of the head and neck, as well as those of the arm of the corresponding side, unite with the same thoracic duct, in the superior part of its course. On the right side, however, a smaller separate duct, formed by the union of the lymphatics of the upper part of that side of the body, is frequently met with, and this empties itself into the right sub-clavian vein. All these lymphatic vessels, in their course, pass through the glands above referred to, and in which the fluid or lymph contained by them doubtless undergoes further elaboration. The lymphatics are remarkable for their equal and small diameter, which allows of the passage of the lymph through them by mere capillary attraction; they are also to be regarded as the chief, though not the exclusive, agents of absorption in the system, the veins likewise taking part in this process.

The lymphatics of the upper and lower portions of the body imbibe and carry along with them the various effete matters and particles which are continually being given off by the older solid constituents of our frame, and which are as constantly undergoing a process of regeneration ; these they redigest and reassimilate, into a fluid endowed with nutritive properties, denominated lymph, and which is poured into the thoracic duct.

Those lymphatics, however, which arise on the surface of the small intestines, and which, passing through the mesentery, join the thoracic duct, have received a special appellation, being called lacteals: this name has been bestowed upon them on account of the milk-like appearance of the fluid which they contain, viz : the chyle, a fluid derived from the digestion of the various articles of food introduced into the stomach, and which also is emptied into the thoracic duct.

But the lacteals are not always filled with chyle; they are only to be found so when digestion has been fully accomplished; when an animal is fasting, they, like other lymphatics, contain merely lymph.

The contents of the thoracic duct likewise vary : it never contains pure chyle, but during digestion a fluid composed of both chyle and lymph, the former predominating, and digestion being completed, it is filled with lymph only.

It follows therefore that, if we are desirous of ascertaining the proper characters of chyle, our observations should not be conducted on the fluid of the thoracic duct, but on that of the lacteals themselves. It is a common error to regard and to describe the contents of that duct, at all times and under all circumstances, as chyle, and it is one which has led to the formation of some false conclusions.

We will describe first the lymph, next the chyle, and lastly the mingled fluid presented to us in the thoracic duct.

The lymph is a transparent colourless liquid, exhibiting a slightly alkaline reaction, and containing, according to the analysis of Dr. G. O. Rees, 0' 120 of fibrin, with merely a trace of fatty matter.

When collected in any quantity, and left to itself, the lymph, like the chyle, separates into a solid and a fluid portion : the solid matter consists of fibrin, and contains mixed up with its substance numerous granular and spherical corpuscles, identical with the white globules of the blood ; the serum is transparent, and contains but few of the corpuscles referred to.

The chyle is a whitish, opaque, oleaginous, and thick fluid, also manifesting an alkaline reaction, and containing, according to the analysis of the gentleman above mentioned, ' 370 of fibrin, and 3 ' 601 of fatty matter.*

  • See article "Lymphatic System," by Mr. Lane, in Cyclopedia of Anatomy and

Physiology, April, 1841.


There are present in it solid matters of several kinds.

1st, Minute particles, described by Mr. Gulliver,* and which constitute the "molecular base" of the chyle, imparting to it colour and opacity : their size is estimated from the 3 @ fo o to the 24^00 0I " an inch in diameter; they are "remarkable" not only for their minuteness, but also for "their equal size, their ready solubility in aether, and their unchangeableness when subjected to the action of numerous other reagents which quickly affect the chyle globules."

Mr. Gulliver has ascertained the interesting fact, that the milky appearance occasionally presented by the blood is due to the presence of the molecules of the chyle. This peculiar appearance of the blood, which so many observers have observed and commented upon, but of which none save Mr. Gulliver have offered any satisfactory explanation, is noticed to occur especially in young and well-fed animals during digestion ; as also in the human subject, in certain pathological conditions, and sometimes in connexion with a gouty diathesis.

2d, Granular Corpuscles, similar to those contained in the lymph, and identical with the white globules of the blood, but rather smaller than those, and which will be fully and minutely described in the chapter on the Blood. Mr. Gulliver, in his excellent article on the chyle, makes the remark that the magnitude of the globules hardly differs, from whatever part of the lacteal system they may have been obtained.

The granular corpuscles are found but sparingly in the chyle of the inferent lacteals, abundantly in that of the mesenteric glands themselves, and in medium quantity in the efferent lacteals, and in the fluid of the thoracic duct.

3d, Oil Globules, which vary exceedingly in dimensions.

4th, Minute Spherules, probably albuminous, the exact size or form of which it is difficult to estimate, and which are not soluble in aether, as are those which constitute the molecular base.

Chyle, when left to itself, like the lymph, separates into a solid and fluid portion : the coagulum, however, is larger and firmer than that of lymph, in consequence of the greater quantity of fibrin which it contains; it is also more opaque, from the presence, not merely of the white granular corpuscles, but principally of the molecules of the chyle; the serum is likewise opaque, the opacity arising from the same cause, the peculiar characteristic molecules of the chyle.

  • See Appendix to the translation of Gerber's General Anatomy, p. 89.


The lymph and the chyle may now be contrasted together. Both are nutritive fluids, the nutritious ingredients contained in the one being derived from the redigestion of the various matters which are constantly thrown off from the older solids, those of the other being acquired from the food digested in the stomach: the one is a transparent fluid, containing but little fibrin, a trace only of oil, and but few white corpuscles; the other is an opaque, white, thick, and oily fluid, more rich in fibrin, and laden with molecules, white corpuscles, oil globules, and minute spherules; the one, therefore, is less nutritive than the other.

It has been asserted that chyle, until after its passage through the mesenteric glands, would not coagulate; the fallacy of this assertion has been demonstrated by Mr. Lane*, who collected the chyle previous to its entrance into those glands, and found that it did coagulate, although with but little firmness, less indeed than it exhibited subsequent to its passage through the glands.

We now come to consider the nature of the contents of the thoracic duct.

These, as already stated, vary according to the condition of the animal; thus, if it be fasting, the duct contains only lymph; if, however, the contents be examined soon after a full meal, they will be found to present nearly all the characters, physical and vital, of the chyle, and in addition, especially in the fluid obtained from the upper part of the duct, a pink hue, said to be deepened by exposure to the air.

This red colour has been noticed by many observers, and it is now generally agreed that it arises from the presence in the fluid of the thoracic duct of numerous red blood corpuscles.

The question is not as to the existence of blood discs in that fluid, but as to the manner in which their presence therein should be accounted for, whether it is to be regarded as primary and essential, or as secondary and accidental.

Most observers agree in considering the presence of blood discs in the chyle of the thoracic duct as accidental, although they account for their existence in it in different ways.

The distinguished Hewsonf detected blood corpuscles in the efferent lymphatics of the spleen, which empty their contents into the thoracic duct, and in this way he conceived that the fluid of that vessel acquired its colour.

  • See Art. " Lymphatic System," loc. cit.
  • Experimental Inquiries, part iii. Edited by Magnus Falkoner. London, 1777,

pp. 122. 112. 135.


The accuracy of Hewson's observation, as to the lymphatics of the spleen containing blood corpuscles, is confirmed by Mr. Gulliver, of the fidelity, originality, and number of whose remarks on the microscopic anatomy of the animal fluids, it is impossible to speak in terms of too high praise. Mr. Gulliver detected blood corpuscles in the efferent lymphatics of the spleen of the ox and of the horse.

Muller, and MM. Gruby and Delafont, attribute the presence of blood discs in the chyle to the regurgitation of a small quantity of blood from the sub-clavian vein: if they are really foreign to the chyle, this is the most probable channel of their ingress.

Mr. Lane thinks that the division of the capillaries, which necessarily takes place in the opening of the duct, allows of the admission into its contents of the blood discs, which are there found. Such are the several ways in which it has been suggested that the blood corpuscles find entrance into the thoracic duct.

Mr. Gulliver has noticed that the blood corpuscles contained in the chyle are usually much smaller than those taken from the heart of the same animal, and also, that not more than one-fourth of the entire number present their ordinary disc-like figure, the remainder being irregularly indented on the edges, or granulated. The first of these observations, viz: that which refers to the smaller size of the blood corpuscles found in the chyle, might be explained by supposing that those corpuscles were in progress of formation, and that they had not as yet attained their full development; the other remark, as to the deformed and granulated character of the corpuscles, might be reconciled with the former explanation, by supposing that some time had elapsed between the death of the animal and the examination of the fluid of the thoracic duct. If this manner of accounting for the condition presented by the blood corpuscles of the chyle should be proved to be insufficient, which I myself scarcely think it will, then the only other mode of explaining their appearances is by supposing that their presence in the chyle is really foreign, and that, soon after their entrance into that fluid, the blood corpuscles begin to pass through those changes, indicative of commencing decomposition, of which they are so readily susceptible.

Leaving, however, for the present the question of the origin of the red corpuscles of the blood, which will have to be more fully discussed hereafter, we will in the next place bestow a few reflections upon the origin of the white corpuscles: into this subject, however, it is not intended to enter at any length at present, but merely to make such observations as seem more appropriately to find their place in the chapter on the Chyle and Lymph.

It has been noticed that the white corpuscles occur in very great numbers in the chyle obtained from the mesenteric and lymphatic glands; this observation has led to the supposition that the white corpuscles are formed in those glands.

Upon this question, as upon so many others, Comparative Anatomy throws much light. It has been ascertained that the glands referred to have no existence in the amphibia and in fishes ; in birds, too, they are only found in the neck. Thus it is evident, that the lymphatic glands, however much they may contribute to the formation of the white corpuscles, are not essential to their production.

Corpuscles, very analogous to those of the chyle and the lymph,

are found in vast quantities in the fluid of the thymus gland in early life : these corpuscles Hewson considered to be identical with the globules of those fluids, and therefore he regarded the thymus gland as an organ of nutrition, and as an appendage to the lymphatic system. In this opinion he has been followed by Mr. Gulliver. That it is an organ of nutrition, adapted to the special exigencies of early life, there can be no doubt ; but that it is an appendage of the lymphatic system, and that the globules with which it so abounds are the same as those of the lymph and chyle, admits of much diversity of opinion.

The globules of the thymus have undoubtedly striking points of resemblance with the corpuscles so frequently alluded to; they have the same granular structure; they are, like them, colourless, and to some extent they comport themselves similarly under the influence of certain reagents.

There are points, however, of dissimilarity as well as of resemblance; thus they are usually very much smaller than the lymph corpuscles, they do not undergo any increase of size when immersed in water, and acetic acid does not disclose the presence of nuclei.

But, above all, the corpuscles of the thymus differ from those of the lymph and chyle in their situation; those of the latter fluids are always enclosed in vessels in lymphatics, or lacteal lymphatics ; while those of the former fluid, that of the thymus gland, are extravascular, lying loosely in the meshes of the cellular tissue which forms the foundation of the substance of the gland itself.

Now, it is impossible to conceive that solid organisms of such a size as the corpuscles of the thymus can enter the lymphatics bodily ; if they are received into the circulation at all, they must first undergo a disintegration and dissolution of their structure.

Both Mr. Gulliver and Mr. Simon* regard the corpuscles of the thymus as cytoblasts; the former, however, believes that before their development as cytoblasts they enter the circulation, while the latter conceives that they are developed in the gland itself into true nucleated cells.

It is difficult to suppose, with Mr. Simon, that the small and uniform granular corpuscles of the thymus are developed into the large, complex and curiously constituted true secreting cells of that gland.

Whether this be the case or not, however, it would appear that Mr. Simon has fallen into a certain amount of error in his account of the structure of the thymus gland, and also of other analogous glands, as well as in the generalizations deduced by him therefrom.

Thus, Mr. Simon states, that in early life there exists in the thymus gland " no trace whatever of complete cells ;" that it is only in later life that nucleated cells are formed, and that these are developed out of the granular corpuscles already referred to, and which are alone present in the gland in the first years of its existence. The same statements are applied to the thyroid body.

But Mr. Simon does not rest here : he regards the long persistence of the corpuscles, which he states are to be found in all those glands which secrete into closed cavities, in the condition of cytoblasts, as constituting a remarkable and important distinction between the glands in question and the true secreting glands which are furnished with excretory ducts.

These observations are to a considerable extent erroneous, as is proved by the fact that true nucleated cells are to be met with abundantly in the thymus gland of still-born children, and also in the thyroid body and supra-renal capsule ; in the last, indeed, almost every cell is nucleated.

On this supposed essential structural distinction between the true glands which are furnished with excretory ducts, and those anomalous ones which are destitute of such ducts, Mr. Simon founds some general deductions.

It is known that the functions performed by the glands without ducts are of a periodic and temporary character, while those discharged by the true glands are of a permanent and constant nature.

  • Prize Essay on the Thymus Gland. London, 4to., 1846.


It is also considered by some physiologists that the nucleus of every nucleated cell is the only true and necessary secreting structure.

These views of the nature of the functions performed by the anomalous glands, and of the importance of the nucleus, being adopted by Mr. Simon, he thence draws the inference that the cytoblastic condition of the cells of the thyroid, thymus, and other analogous glands, is precisely that which is required by organs which are called only into action periodically, and in which great activity prevails at certain periods.

This theory is ingenious, but it has been seen that the main fact upon which it rests is for the most part erroneous ; and, the basis of the theory being removed, the theory itself must fall.

In order that it may be seen that the opinions entertained by Mr. Simon, in his Essay on the Thymus, have not been over-stated, I will introduce a few passages therefrom :

"Thus, while the completion of cells, within the cavities of the thyroid gland, is assuredly a departure from the habitual state of that organ, and probably the evidence of protracted activity therein ; it is yet just such a direction as may serve even better than uniformity to illustrate the meaning of the structures which present it; for it shows, beyond dispute, that the dotted corpuscles are homologous with the cytoblasts of true glands." (p. 79.)

"In the thymus one would at first believe a similar low stage of cell development to be universal ; for in examining the contents of the gland in early life, one finds no trace whatever of complete cells. The dotted corpuscles are undoubtedly quite similar to those which we have recognised as becoming the nuclei of cells in the thyroid body, and in other organs ; there is abundant room for conjecturing them to be of a correspondent function — to be, in fact, true cytoblasts; ■but the arguments for this point cannot be considered quite conclusive, without some additional evidence."

" The completion of a cell, from the isolation of so much of the secreted product as is collected round each cytoblast, is a very frequent secondary process. In the true glands it is very frequent, in those without ducts exceptional." (p. 84.)

With one other remark on the corpuscles of the thymus, we will conclude this short chapter; mixed up with those corpuscles are frequently to be noticed many nucleated globules, in every way similar to the white corpuscles of the blood, but very distinct from the true cell corpuscles of the gland; the nucleus of these white globules is of nearly the same size as the dotted corpuscles themselves. Is there any relation between this coincidence in size ?

We now pass to the consideration of the most important fluid in the animal economy, viz: the blood.


[The lacteals have their origin in the villi of the intestines, while the lymphatics originate throughout the body in the various tissues and organs of which it is composed.

These latter vessels are arranged in a superficial and deep set ; the superficial running underneath the skin, or under the membranous coats, immediately enveloping the organs in which they are found, while the deep lymphatics usually accompany the deep-seated blood vessels. They usually exceed the veins in number, but are less in size, and anastomose more frequently than the accompanying veins. The origin of the lymphatics may be either superficial or deep : in the first mode, they usually arise in the form of net-works, or plexuses, out of which single vessels emerge at various points, and proceed directly to the lymphatic glands, or to join larger lymphatic vessels.

These plexuses consist of several strata, becoming finer as they approach the surface, both in the calibre of the vessels and closeness of reticulation. When the lymphatics have a deep origin, their precise mode is not so easily made out : it is probably the same as when they arise superficially.

STRUCTURE.

The lymphatic vessels, in their structure much resembling veins, have thinner and more delicate coats ; some are quite transparent.*

For an account of structure of lacteals, see page 492.

The medium-sized and larger lymphatic vessels, according to Mr. Lane,f have three coats ; viz : an internal, a middle or fibrous, and an external, one, analogous to the external or cellular coat of the blood-vessels.

The inner tunic is thin, transparent, and elastic, but less elastic than the others, being the first to give way when the vessel is unduly distended : like the blood-vessels, it is lined with a layer of scaly or tesselated epithelium, as in the blood-vessels. The middle or fibrous coat is very elastic, and consists of longitudinal fibres having the characters of the plain involuntary muscular fibres, freely mixed with fibres of cellular tissue. Herbst, Henleij: and others, describe, with these longitudinal fibres, others of transverse and oblique direction : these are very few in number, the great majority being longitudinal. The external or cellular coat is elastic, and composed of interlaced fasciculi, of areolar tissue, mixed with some elastic fibres.

The lymphatics receive vasa vasorum, which ramify in their middle and outer coats; nerves distributed to them have not yet been discovered, al though their existence has been inferred on physiological grounds. The} are also endowed with vital contractility.

  • Quain's "Anatomy," 5th edition, by Sharpey and Quain.
  • "Cyclop, of Anatomy and Physiology," art. "Lym. System."
  • Henle, " Algemeine Anatomie," Leipzig, 1841.


The lymphatics and lacteals are supplied with valves in the same manner as the veins, and for like purposes. They usually consist of two semi-lunar folds, but variations occasionally occur. They are altogether wanting in the reticularly arranged vessels, which compose the plexuses of origin before spoken of; but where they exist, they follow one another at shorter intervals than in the veins.

Mr. T. Wilkinson King (Guy's Hospital Reports, April, 1840,) has calculated the entire number of valves in the lymphatic system at 30,000, while the veins only contain about 5,000.

The lymphatics of fish and amphibia are usually destitute of valves, and may be injected from the trunks : in birds, valves are less numerous than in the lymphatics of the mammiferous animals.

" No lymphatics have yet been traced in the substance of the brain or spinal cord, though they exist in the membranous envelopes of these parts, nor have they been detected within the eye-ball, or in the placenta or foetal envelopes. Although no absorbent or open orifices have been discovered in the lacteals or lymphatics, yet it is probable, that both the lymph and chyle corpuscles are developed as cells within the vessels; according to one view, these corpuscles of lymph, may be developed from the liquid part of the lymph, which serves as a blastema. In this case, the nuclei may be formed by aggregation of matter round nucleoli, which again may be derived as germs from other cells; or, as Henle is disposed to think, two or more fat particles may unite to form a nucleus ; upon another view, it may be conceived that these corpuscles are formed on the inner surface of the walls of their containing vessels, as epithelium or mucous corpuscles are produced on their supporting membrane, and that this process may be connected with the absorption of lymph or chyle with the vessels, in the same manner as secretion into a gland-duct, or other receptacle, is accompanied by the formation and detachment of cells."*

MANIPULATION

To procure lymph and chyle quite pure, it is necessary to take the first from the lymphatic glands, and the second from the lacteals themselves. Wagner has found dogs the best subjects for such experiments in comparative anatomy, and on the surface of the liver and spleen, are commonly found turgid lymphatic vessels, from which pure lymph may be obtained. It may also be obtained quite pure by opening the thoracic duct of an animal that has fasted for some time before being killed.

The chemical analysis of chyle usually quoted, is that of the ass, made by Dr. Rees, and of the cat, made by Nasse.

Dr. Rees has examined the fluid contained in the thoracic duct of a human subject, a criminal, an hour and a half after execution. From the small quantity of food taken for some hours before death, the fluid must have consisted principally of lymph. It had a milky hue, with a slight tinge of buff. Its analysis, compared with that of the chyle of the ass, given in the text, shows less water, more albumen, and much less fat.


  • Quain's "Anatomy," by Sharpey and Quain, 5th edition.


The chyle-corpuscles are most numerous in the chyle taken from the mesenteric glands.

The lymph corpuscles, though closely resembling the colourless corpuscles of the blood, hereafter described, are rather less in size, and not so uniformly round.

The globules of chyle and lymph, also, differ in structure from the pale globules of blood : in the last, two, three or four nuclei are easily seen when the envelope is made more or less transparent, by acetic, sulphureous, citric, or tartaric acid. But globules of lymph and chyle, like the nuclei of red corpuscles of blood, are only rendered more distinct, and slightly smaller by any of these acids ; so that the central parts present no regular nuclei, or divided nucleus, such as are contained in pale globules of blood. In the larger lymphatics and thoracic duct, are found corpuscles identical in size and structure to the pale corpuscles of blood. When fresh, the corpuscles of lymph and chyle swell on being mingled with pure water, as does the nucleus of blood corpuscle. Mixed with a strong alkali, or neutral salt, the globule becomes partially dissolved, mis-shapen, or fainter, forming a ropy and tenacious compound with the fluid. According to Gulliver, the average measurements of the corpuscles of lymph and chyle are the same, viz : -rJW of an English inch. Mr. Gulliver measures the colourless corpuscles of the blood 3 ^V o °f an mc ^' or about 1 larger than the lymph and chyle corpuscles.*

For the purposes of examination and study of the corpuscles of lymph or chyle, it is necessary to place a very small drop obtained from either of the sources already mentioned, on a plain glass slide, wiped perfectly clean and dry, and cover it immediately with a piece of thin glass. It is then ready for examination with a ith or ith-inch object glass. Sometimes the corpuscles will be better observed after the lymph is diluted with serum. After examination in this way, the different reagents may be applied, by introducing any one of them by means of a pipette upon the edge of the thin covering glass ; by means of capillary attraction, the reagent will gradually insinuate itself under the glass, and its effects must be constantly observed with the microscope.

Plate LXX., fig. 1, exhibits corpuscles of lymph. Fig. 2, exhibits corpuscles of chyle. Plate LXXIII., fig. 1, exhibits a lymphatic gland, and lymphatic vessels.]

  • Hewson's Worn uied by Gulliver, published for Sydenham Society, page 253.


Article II. — The Blood

Of all the fluids in the animal economy, the most interesting and the most important is the Blood : and it is an appreciation of this fact which has led to the concentration upon its study, in times past as well as present, of the powers of a host of able and gifted observers, whose labours have not been without their reward.

The knowledge of this fluid acquired by the early physician was of a very limited character, it being confined to the observance of a certain number of external and obvious appearances, such as the colour, consistence, and form of the effused blood. Limited as this knowledge was, however, compared with that which, in our favoured day, we enjoy, it was not without its practical utility.

More recently, the chemist, who is in these times extending in all directions so rapidly the boundaries of his domain, has cast upon this peculiar portion of it a flood of light. Who, to look upon a dark and discoloured mass of blood, could imagine that the magic power of chemistry could reveal in it the existence of not less than forty distinct and essential substances ?

Lastly, the micrographer, with zeal unweariable, has even outstripped the progress of his rival the chemist, and brought to light results of the highest importance. It is these results that in this work we have more especially to consider.

In the following pages we shall have to treat of the blood under various aspects and conditions ; we shall have to regard it alive and dead, circulating within its vessels, and motionless without them ; as a fluid and as a solid; healthy and diseased; or, in other words, we shall have to consider the blood physiologically, pathologically, and anatomically.

  • Those who wish to learn the comparative size of the hlood corpuscles in the

different vertebrate animals, may find a very complete table of their measurements in the "Proceedings of the Zoological Society, No. 152," carefully prepared by Mr. Gulliver; or " He wson's Works," published for the Sydenham Society, and edited by Mr. George Gulliver, pp. 237 — 243: or "Gerber's General Anatomy," edited by Gulliver — Appendix, pp. 31 — 84.


The blood may be defined as an elaborated fluid, having usually a specific gravity of about 1055, that is, heavier than water; in mammalia and most vertebrate animals, being of a red colour, but colourless in the invertebrata;* circulating in distinct sets of vessels, arteries, and veins; holding in solution, all the elements of the animal fabric — fibrin, albumen, and serum, together with various salts and bases, and in suspension, myriads of solid particles, termed globules. f

The blood would thus appear to be the grand supporter and regenerator of the system; in early life, supplying the materials necessary for the development of the frame, and, in adult existence, furnishing those required for its maintainance : hence "the blood" has been figuratively called "the life."

COAGULATION OF THE BLOOD, WITHOUT THE BODY.

The first change which the blood undergoes subsequent to its removal from the body consists in its coagulation. This phenomenon has been denominated emphatically, "the death of the blood," because, when it has once occurred, the blood is thereby rendered unfit to maintain the vital functions, and there is no known power which can restore to it that faculty.

Although the word coagulation is usually applied generally to the blood, yet it not to be understood that the whole of the mass of that fluid undergoes the change of condition implied by the term coagulation, which affects but a single element of the blood, viz : the fibrin.

The precise circumstances to which the coagulation of the blood is due, have never as yet been satisfactorily explained and determined. Some have conceived that it resulted from the escape of a vital air or essence. Much has been said and written upon this "vital principle," and, it seems to me, with very little profit. It would be more philosophical, I think, to regard animal life not as an essence, or aether, but as the complex operation of nicely-adjusted scientific adaptations and principles. According to this view, the human frame in health would be comparable (and yet, withal, how incomparable is it!) to a finelybalanced machine, in which action and reaction are proportionate, and in disease disproportionate, the injury to the machine being equivalent to the disproportion between the two forces.*


  • Miiller states that the quantity of blood in the system varies from eight to

thirty pounds, and Valentin found that the mean quantity of Wood in the male adult, at the time when the weight of the body is greatest, viz : at thirty years, is about thirty-four and a half pounds, and in the adult female, at fifty years, when the weight of the body in that sex is at its maximum, about twenty-six pounds. According also to Miiller, the specific gravity of the blood varies from 1-527 to 1 *057 ; arterial blood is lighter than venous.

  • In one vertebrate animal, a fish, Branchiostoma lubricum Costa, the blood is

colourless, and in the most of Annelida it is red ; the red colour, however, exists in the liquor sanguinis, and not in the blood corpuscles.



The coagulation of the blood, in some degree, doubtless depends upon the operation of the following causes, each contributing in a greater or lesser degree to the result ; namely, the cessation of nervous influence, the abstraction of caloric, the exercise of chemical affinity between the particles of fibrin, and, lastly, a state of rest: between motion and life a very close connexion appears to exist.f

Formation of the Clot.

A portion of blood having been abstracted from the system, and allowed to remain for a few minutes in a state of quiesence, in a basin or other suitable vessel, soon manifests a change of condition. This consists in the separation of the fibrin and globules of the blood, which go to form the clot, from the serum, which holds in solution the various salts of the blood. In this way a rude and natural analysis is brought about; the fibrin, being heavier than the serum, falls to the bottom, and, by reason of its coherence and contractility, forms a compact mass or clot, the diameter of which is less than that of the vessel in which it is contained ; while the lighter serum floats on the top and in the space around the clot.

Now, the only active agent in this change in the arrangement of the different constituents of the blood, is the fibrin; and although the globules of the blood constitute a portion of the clot, yet they take no direct part in its formation, and their presence in it is thus accounted for; the fibrin, in coagulating, assumes a filamentous and reticular structure, in the meshes of which the globules become entangled, and thus are made to contribute to the composition of the clot, the bulk of which they increase, and to which they impart the red colour.


  • It is hoped that the preceding brief remarks will not expose the writer to the

charge of being a Materialist ; between animal life and mind an essential distinction exists.

f " Fresh blood, if exposed to a very low temperature, freezes, and may in that state be preserved, so as to be still susceptible of coagulation when thawed." — Mullek.

It was an ancient theory that the clot was formed solely by the union of the globules with each other. The fallacy of this opinion is easily demonstrated by the two following decisive experiments:

The first is that of Muller, on the blood of the frog, who separated, by means of a filter, the globules from the fibrin, the latter still forming a clot, although deprived of the globules. This experiment is not, however, applicable to the blood of man, or of mammalia in general, the globules in these being too small to be retained by the filter. The second expedient is, however, perfectly suited to the human blood. It is well known that if blood, immediately after its removal from the body, be stirred with a stick, the fibrin will adhere to it in the form of shreds ; the blood being defibrinated by this means, the globules fall to the bottom of the basin in which the blood is contained, on account of their gravity; but they do not cohere so as to form a clot, remaining disconnected and loose.

It is difficult to determine the exact time which the blood takes to coagulate, because this coagulation is not the work of a moment; but, from its commencement to its completion, the process occupies usually several minutes. The first evidence of the formation of the clot, is the appearance of a thin and greenish serum on the surface of the blood, in which may be seen numerous delicate fibres, the arrangement of which may be compared to that of the needle-like crystals contained in the solution of a salt in which crystallization has commenced. Estimating, however, the coagulation neither from its commencement nor from the complete formation and consolidation of the clot, but from the mean time between these two points, it will generally be found that healthy blood coagulates in from fifteen to twenty minutes.

In diseased states of the system, however, the time occupied in the coagulation of the blood, or, in other words, in the formation of the crassamentum, or clot, varies very considerably; and it is of much practical importance that the principle which regulates this diversity should be clearly understood.

In disorders of an acute, active, or sthenic character, in which the vital energies may be regarded as in excess — as, for instance, in inflammatory affections, in pneumonia, pleurisy, acute rheumatism, and sanguineous apoplexy : in febrile states of the system, as in the commencement of some fevers, as in ague, plethora, and as in uterogestation — the blood takes a much longer time than ordinary to coagulate, no traces of this change in the passage of the blood from a fluid to a solid state being apparent until from sixteen to twenty minutes have elapsed. This length of time may be accounted for, by supposing that, in the affections named, the blood is endowed with a higher degree of vitality, and that therefore a longer period is required for its death to ensue ; or, in other words, if the expression may be allowed, that the blood in such cases dies hard. On the contrary, in disorders of a chronic, passive, or asthenic character, in all of which there is deficiency of the vital powers — as in typhus, anemia, chlorosis — the blood passes to a solid state in a much shorter period than ordinary, even in from five to ten minutes. In these cases the vitality of the blood is very feeble, and it may be said to die easily. A remarkable difference is likewise observable in the characters of the clot formed in the two classes of disorders named ; in the first it is firm, and well defined; in the second, soft, and diffluent.* To this subject we shall have occasion again to refer, more at length.

Fibrin, if left at rest for a time, undergoes a softening process, and breaks up into an extremely minute granular substance. This softening of the fibrin has been improperly confounded with suppuration; the softened mass, however, may be distinguished from true pus by the almost complete absence of pus globules. This peculiar change in the condition of the fibrin has been noticed to occur both in TDlood contained within and without the body, and large softened clots of it are not unfrequently encountered in the heart after death. The process always commences in the centre of these clots.

Formation of the Buffy Coat of the Blood.

Surmounting the coloured portion of the clot is observed, in blood taken from the system in inflammatory states, a yellowish-green stratum ; this constitutes the buffy or inflammatory crust, the presence of which was deemed of so much importance by the ancient physician, and which is indeed not without its pathological value. This crust consists of fibrin deprived of the red globules of the blood; and its mode of formation is thus easily and satisfactorily explained. Of the constituents of the blood, the red globules are the heaviest; now, supposing that no solidification of any one element were to take place, these, of course, would always be found occupying the lowest position in the containing vessel ; the fibrin would take the second rank, and the serum the third : but such, under ordinary circumstances, not being the case, and the fibrin coagulating so speedily, the globules become entangled in its meshes before they have had sufficient time given them to enable them to obey fully the impulse derived from their greater specific gravity ; and thus no crust is formed. In blood drawn in inflammations, however, this coagulation, as already stated, proceeds much more slowly; and thus time is allowed to the globules to follow this impulse of the law of gravity to such an extent, as that they fall a certain distance, about the sixteenth of an inch, usually, below the surface of the fibrin, before its complete coagulation averts their further progress; and a portion of which is thus left colourless, which constitutes the buffy and so-called inflammatory crust of the blood. But there are other considerations to which it is necessary to attend, and which contribute to the formation of the buffy coat.


  • It is to be remarked, that the clot is not of equal density throughout, but that

its lower portion is invariably softer than the upper, and this is accounted for by the fact of its containing less fibrin.



One of these is the greater relative amount of fibrin which inflammatory blood contains.

A second is the increased disposition, first pointed out by Professor Nasse, which the red corpuscles have in inflammatory blood to adhere together and to form rolls, and the consequence of which is that they occupy less space in the clot.

A third additional consideration, to which it is necessary to attend, in reference to the formation of the inflammatory crust, is the density of the blood, which bears no exact relation to the amount of fibrin, but depends rather upon the quantity of albumen which it contains.* The greater the density of the blood, the longer would the globules take to subside in that fluid ; and the less its density, the shorter would that period be. Now, inflammatory blood is usually of high density, while with that of feeble vitality, the reverse obtains. Thus, were it not for the fact, that in blood in the first state, coagulation is slow, and in the second quick, the blood of weak vital power would be that in which, a priori, we should expect to see the buffy coat most frequently formed ; but the much greater rapidity in the coagulation of the blood more than counterbalances the effect of density.

The blood, then, may be so dense, that although at the same time it coagulates very slowly, yet no inflammatory crust be formed, the patient from whom the blood is extracted labouring all the while under severe inflammation. An ignorance of this fact has been the source of many great and perhaps fatal errors, on the part of those physicians who have been used to regard the presence of the buffy coat as an undoubted evidence of the existence of inflammation, and its absence as indicating immunity therefrom. It has been remarked that, in the first bleedings of pnemonic patients, the blood often wants the buffy coat; this is attributed to its greater density, and which is found, to diminish with each succeeding abstraction of blood; so that if inflammation be present, the characteristic coat is usually apparent also after the second bleeding.

  • It has been remarked, that in albuminuria, in which a considerable portion of

the albumen of the system passes off with the urine, the blood possesses a very feeble density.


The conditions, then, favourable to the formation of the buffy coat, are a mean density of the blood, slow coagulation, excess of fibrin, and increased disposition to adherence on the part of the red corpuscles.

Other circumstances doubtless exist, which in a minor degree affect the formation of the crust : such as the density of the globules, and the qualities of the fibrin itself. Into these it is unnecessary to enter, as they do not vitiate the accuracy of the general statements.

The Cupping of the Clot.

At the same time that the crassamentum exhibits the buffy coat, the upper surface of the clot is very generally also cupped. This cupping of the clot arises from the contraction of that portion of the fibrin which constitutes the buffy stratum, and which contraction operates with greater force on account of the absence in it of the red corpuscles of the blood. The degree to which the clot is cupped, therefore, probably is in direct relation with the thickness of the crust. Its presence was also regarded as an indication of the existence of inflammation, the amount of cupping denoting the extent of inflammation. This sign is not, however, any more than that afforded by the buffy coat, to be considered as an invariable criterion of the existence of inflammation.*

  • Professor Nasse has pointed out a mottled appearance which is frequently

observed to precede the formation of the buffy coat, and the existence of which he states to be quite characteristic of inflammatory blood. This appearance is produced in the following manner : after the lapse of a minute or two, a peculiar heaving motion of the threads or rolls formed by the union of the red corpuscles with each other is observed to take place ; this results in the breaking up of the rolls, the corpuscles of whieh now collect into masses, leaving, however, intervals between them, and which become filled with fibrin ; now, it is the contrast in colour between this fibrin and the masses of red corpuscles which occasions the blood in coagulating to assume the mottled aspect referred to.


COAGULATION OF THE BLOOD, IN THE VESSELS AFTER DEATH.

The coagulation, or death, which we have described as occurring in blood abstracted from the system by venesection, takes place likewise — the vital influence which maintains the circulation being removed — in that which is still contained within the vessels of the body, although in a manner less marked and appreciable.

As also in the case of the blood withdrawn from the system, the time occupied in the coagulation of that which is still enclosed in its own proper vessels, varies very considerably. This difference depends partly upon the circumstances under which the patient has died, whether he has been exhausted or not by a previous long and wasting illness, and partly upon temperature and, perhaps, certain electric states of the atmosphere. In all instances, however, a much longer period is required for the production of coagulation in blood not removed from the body, than in that which has been withdrawn by bleeding; this change in its condition being seldom effected, in the former instance, in a shorter period than from twelve to twenty-four hours subsequent to decease ; although occasionally, but rarely, it may occur at periods either earlier or later than those named.

Signs of Death. — It has already been stated, that blood once coagulated is rendered unfit for the purposes of life, and that no known means exist capable of restoring to coagulated blood its fluid state, so as to render it once again suited to play its part in the maintenance of the vital functions. The accuracy of these statements is attested by physiology, which demonstrates to us that a fluid condition is necessary to the blood, for the correct performance of its allotted functions. It follows, then, from the foregoing, that a coagulated state of the blood, not in a single vessel indeed, but in the vessels of the system generally, affords a certain indication that death has occurred, and that therefore a return to life has become impossible.

It has ever been an object of the highest importance to distinguish real from apparent death; and anxious searches have been instituted in the hope of discovering some certain sign whereby the occurrence of death is at once signalized. Hitherto this inquiry has been unsuccessful; and it could hardly have been otherwise; for before the physiologist will be able to determine the precise moment when life ceases, and death begins, he must know in what the life consists, for death is but the negation of life. It is probable that the mystery of life will never be revealed to man ; if, indeed, it be any thing more than, as already hinted, the result of the combined operation of various chemical and physical laws appertaining to matter.

Although no one single sign has hitherto been discovered indicative of death at the moment of its occurrence, yet several appearances have been remarked some time after death, all of which are of more or less value in determining so important a point. Independently of the cessation of respiration and circulation, the presence of muscular rigidity, some other changes have been noticed to occur in different parts of the human body soon after the extinction of life; as, for instance, in the eye, and in the skin: these are mostly, however, symptomatic of incipient decomposition, and the time of their accession is very uncertain: they likewise affect parts, the integrity of which is not essential to life. A fluid state of the blood, on the contrary, has been shown to be indispensable to life; so that the change which it undergoes in the vessels of the body so quickly after death, may be employed with much advantage and certainty in determining, in doubtful cases, whether life has become extinct or not.

It is by no means difficult to establish the fact of the coagulation of the blood in the vessels after death. If a vein be opened, as in the ordinary operation of bleeding, in a person who has just died, the blood will issue in a fluid state, as in life ; but it will not leap forth in a stream. If a little of the blood, thus procured, be preserved in a small glass, we shall soon remark the occurrence of coagulation in it, from which we shall know that the fibrin within the vessels has not as yet assumed a solid form. If we repeat this operation at the end of about eighteen hours, we shall obtain only a small quantity of reddish serum, in which, on being set aside for a time, no crassamentum will be found, the only change occurring in this serum consisting in the subsidence of the few red globules which were previously suspended in it, and which now form, at the bottom of the glass, a loose and powdery mass. By this experiment, which may be repeated on several veins, and even on an artery, we have clearly established the fact of the coagulation of the blood within the vessels of the body, and therefore have ascertained, in a manner the most satisfactory, that life is extinct.

In some instances, the blood is said to remain fluid after death: this statement is not strictly correct, as a careful examination of such blood will always lead to the detection of some traces of coagulation. To the subject of the fluid condition of the blood after death, we shall have hereafter to return, in treating of the pathology of the blood.


When it is recollected that the heat of some climates, and the laws and usages of other countries, compel the interment of the dead a very few hours after decease, the importance of this inquiry will become apparent ; and the value of any sign which more certainly indicates death than those usually relied upon in determining this question, will be more fully appreciated.

It cannot be doubted but that, from the insufficient nature of the signs of death usually regarded as decisive, premature interment does occasionally take place ; and it is probable that this occurrence is far less unfrequent than is generally supposed, and that for each discovered case, a hundred occur in which the fatal mistake is never brought to light, it being buried with the victim of either ignorance or carelessness.*

We have now to proceed to the anatomical consideration of the blood ; we have to pass to the description of the solid constituents of that fluid, the globules ; to describe their different kinds, their form, their dimensions and their structure ; their origin, their development, and their destination, their properties, and their uses.

THE GLOBULES OF THE BLOOD.

The blood is not an homogeneous fluid, but holds in suspension throughout its substance a number of solid particles, termed globules. These serve to indicate to the eye the motion of the blood ; and were it not for their presence, we should be unable to establish, microscopically, the fact of the existence of a circulation, to mark its course, and to estimate the relative speed of the current in arteries and veins under different circumstances.

These globules are so abundant in the blood, that a single drop contains very many thousands of them, and yet they are not so minute but that their form, size, and structure, with good microscopes, can be clearly ascertained and defined. They are not all of one kind, but three different descriptions have been detected — the red globules, the white, and certain smaller particles, termed molecules. We shall take each of them in order; and notice, in the first place, the red globules, f

  • The coagulation of the blood may he retarded or altogether prevented by its

admixture with various saline matters : to this point we shall have occasion to refer more fully hereafter.

  • Malpighi first signalized the existence of the red globules in the blood, so far

back as 1665: he regarded them as of an oily nature. The words in which this discovery was recorded were as follow: "Sanguineum nempe vas in omento hystricis . . . in quo globuli pinguedinis propria figura terminati rubescentes et corallorum rubrorum vulgo coronam Eemulantes . . ." — De Omento et adiposis Ductibus. Opera omnia. Lond. 1686.


THE RED GLOBULES.


The number of red globules existing in the blood surpasses by manytimes that of the white. To the sight, when seen circulating in this fluid, they appear to constitute almost the entire of its bulk. We shall now have to consider their form, the size, the structure, and the properties by which they are characterized.

Form. — In man, and in most mammalia, the red blood corpuscles are of a circular, but flattened, form, with rounded edges, and a central depression on each surface, the depth of which varies according to the amount of the contents of each globule.* Such is the normal form of the blood discs, or the shape proper to them while circulating in the blood of an adult. (See Plate I. fig. 1.) In that of the embryo, the depression is wanting, and the globules are simply lenticular. f

The blood globules, however, like all minute vesicles, possess the properties of endosmosis and exosmosis. These principles depend for their operation upon the different relative density of two fluids, the one external to the vesicle, the other internal. When these two fluids are of equal density, then no change in the normal form of the vesicles occurs : when, however, the internal fluid is of greater density than the external, then an alteration of shape does take place ; endosmosis ensues, in which phenomenon a portion of the liquid without the vesicle passes through its investing membrane, and thus distends and modifies its form. Lastly, when a reverse disposition of the fluids exists, a contrary effect becomes manifested; exosmosis is the result; this implies the escape of a portion of the contents of the vesicle into the medium which surrounds and envelopes it. The operation of these principles is beautifully seen, not merely in the blood globules, but more especially in those exquisitely delicate formations, the pollen granules.


Leeuwenhoek was, however, the first observer who distinctly described the blood globules in the different classes of animals: this he did in 1673. These historical reminiscences are not without their interest, and further references of this kind will be introduced in the course of the work.

  • The central depression was first noticed by Dr. Young. The flattened form with

the central depression on each surface, and of which a bi-concave lens would form an apt illustration, is that which any vesicle partially emptied of its contents would assume.

f Hewson figured the difference in the form of the blood globule in the embryo, and in the adult, in the common domestic fowl, and in the viper.


Between the density of the liquid contained within the red globules, and that of the liquor sanguinis, in states of health, a nice adaptation or harmony exists, whereby these globules are enabled to retain their peculiar form. There is, however, scarcely any other fluid which can be applied to the globules which does not, more or less, affect their shape, most of the reagents employed in their examination rendering them spherical. (See plate I. fig. 3.)

From the preceding observations, therefore, it follows that the red globules, to be seen in their normal condition, should be examined while still floating in the serum : they are best obtained by pricking the finger with a needle or lancet.

Usually, when the microscope is brought to bear upon the objectglass, the globules are seen to be scattered irregularly over its surface, the majority of them presenting their entire disc to view, others lying obliquely, so as to render apparent the central depression, and others again exhibiting their thin edges, (See Plate I. fig. 1.) Not unfrequently, however, a number of corpuscles unite together by their flat surfaces, so as to form little threads, comparable to strings of beads, or of coins, which are more or less curved, and in which the lines of junction between the corpulscles are plainly visible. These strings of compressed globules bear also a close resemblance to an Oscillatoria, and a still closer likeness to the plant described in the history of the British Fresh- water Algae, under the name of Hcematococcus Hookeriana. (See Plate I. fig. 4.) The cause which determines this union of the cells still requires to be explained, and would seem to be referable to a mutual attraction exerted by the globules on each other. Andral asserts that when the fibrin of the blood is abstracted, they do not thus cohere. Professor Nasse, as already remarked, states that this disposition on the part of the red corpuscles to unite together and form rolls (as of miniature money in appearance), is increased in inflammatory blood. The union does not, however, last long; a heaving to and fro of the strings of corpuscles soon taking place, and which terminates in their disruption.*

  • In reptiles, birds, and fishes, the red globules are elliptical, a form possessed also

by some few mammalia, chiefly of the family CamelidcE. This fact was discovered by Mandl, in the dromedary and paco ; and subsequently by Gulliver, in the vicugna and llama. The oval globules of these animals, however, could not be confounded with those of reptiles, buds, and fishes, than the corpuscles of which they are so much smaller, and, further, are destitute of the central nucleus, which characterizes the blood globules of all the vertebrata,the mammalia alone excepted. The long diameter of the blood corpuscles of the dromedary, Mr. Gulliver states to be the s^sx of an inch, and its short the j^y ; the first of these measurements exceeds but little the diameter of the human blood corpuscles.


Size. — The size of the red corpuscles of the blood, although more uniform than that of the white, is nevertheless subject to considerable variation. Thus, the globules contained in a single drop of blood are not all of the same dimensions, but vary much. These variations are, however, confined within certain limits: the usual measurement in the human subject is estimated at about the 3 5V0 °f an d inch; but, occasionally globules are met with not exceeding the TI j T ; and, again, others are encountered of the magnitude of the 32V 9 °f an mcn > tnese are, however, the extreme sizes which present themselves.* The difference in the size of the red corpuscles, which has been indicated, is a character common to them in the blood of all persons, and at every age. Another variation as to size exists, which is, that the corpuscles are larger in the embryonic and fetal than they are in adult existence. f This observation is important, inasmuch as it seems to pi'ove that the blood does not pass directly from the maternal system into the fetal circulation, but that the corpuscles are formed independently in the fetus. In states of disease, also, it has been remarked by Mr. Gulliver that there is even a still greater want of uniformity in the measurements presented by the red corpuscles.


Among fishes, one exception to the usual oval form of the blood corpuscle has been met with: this occurs in the lamprey, the blood disc of which Professor Rudolph Wagner observed to be circular ; in form then the blood corpuscles of the lamprey agrees with that of the mammalia, but in the presence of a nucleus, the existence of which has been recently ascertained by Mr. T. W. Jones, it corresponds with the structure of the blood discs of other fishes.

  • The first measurement given is that which is usually adopted by writers ; the

last two are those made by Mr. Bowerbank for Mr. Owen, and which are to be found in the latter gentleman's paper on the Comparative Anatomy of the Blood Discs, inserted in the Lond. Med. Gazette for 1839. The measurements which I have made of the human blood corpuscle do not accord with those which are generally regarded as correct : thus I find the average diameter of the blood globule of man to be, when examined in the serum of the blood, about the -g-gVn °f an i nc h> an( i m water in which the corpuscles are smaller, as a necessary consequence of the change of form, the 3^. The micrometer employed by me is a glass one, precisely similar to that made use of by Mr. Gulliver, being furnished to me by the same eminent optician, Mr. Ross, from whom his own was obtained.

f This is the opinion of Hewson, Provost, and Gulliver, and I have myself to some extent confirmed its accuracy.


A careful examination of the elaborate tables of Mr. Gulliver on the measurements of the blood corpuscles, appended to the translation of Gerber's Minute Anatomy tends to show that a general though not a very close or uniform relation, exists between the size of the blood corpuscles among the mammalia, and that of the animal from which they proceed. These tables furnish more evidence in favour of this co-relation than they do in support of the assertion that has been made, that the dimensions of the corpuscle depend upon the nature of the food. It would appear, however, nevertheless, that the corpuscles of omnivora are usually larger than those of carnivora, and these, again, larger than those of herbivora* In a perfectly natural family of mammalia, as the rodents or the ruminants, there is also an obvious relation between the size of the corpusucle and that of the animal. Gerber states that there is an exact relation between the size of the blood globules and that of the smallest capillaries. This observation is doubtless strictly correct.

Structure. — Much diversity of opinion has, until recently, prevailed, and does still obtain, although to a less extent, in reference to the intimate structure of the red globule. This diversity has arisen partly from the imperfections of the earlier microscopic instruments employed in the investigation, and in part is due to the different circumstances in which observers have examined the blood corpuscle. Thus, one micrographer would make his observations upon it in one fluid, and another in some other medium, opposite results and conclusions not unfrequently being the results of such uncertain proceedings. These discrepancies it will be the writer's endeavour, as far as possible, to reconcile with each other, as well as to point out those observations which are entitled to our implicit belief, and those which yet require confirmation. This being done, we shall be in a position to form some certain conclusions. The earlier microscopic observers believed, almost without exception, in the existence of a nucleus in the centre of each blood corpuscle. Into this belief they were no doubt led more from analogy than from actual observation. Now, analogy, although frequently useful in the elucidation of obscure points, affords in the present instance but negative and uncertain evidence. In the elliptical blood discs of reptiles, birds, and fishes, a solid granular nucleus does undoubtedly exist; but the best optical instruments, in the hands of the most skilful recent micrographers, aided by the application of a variety of reagents, have failed, utterly, in detecting the presence of a similar structure in the blood globule of the human subject in particular, and of mammalia in general. I therefore do not hesitate to join my opinion to that of those observers who deny the existence of a nucleus in the blood discs of man and mammalia.*



  • The largest globules which have as yet been discovered, are those of the

elephant; the next in size, those of the capybara and rhinoceros; the smallest, according to the observations of Mr. Gulliver, are those of the napu musk-deer. The corpuscles of the blood of the goat were formerly considered to be the smallest. The following are the dimensions given by Mr. Gulliver of some of the animals above named. Diameter of corpuscle of the elephant, the -^ -$ of an inch ; of capybara the 32Y3 5 of goat, the -5^; and of napu musk-deer j^^rs- The white corpuscles of the musk-deer are as large as those of a man; a proof that the red corpuscles are not formed, as many suppose, out of the colourless blood globules. (See the figs.)



The appearance of a nucleus is, indeed, occasionally presented; but this appearance has been wrongly interpreted. An internal small ring, under favourable circumstances, may be seen in the centre of each blood corpuscle : this ring is occasioned by the central depression, the outer margin of which it describes; and it was the observance of it that gave to Delia Torre the erroneous impression, that each globule had a central perforation, and therefore was of an annular form ; and further, probably induced Dr. Martin Barry to describe it as a fibre.

The very existence, on both surfaces of the blood disc, of a deep central depression, together with its little thickness, almost preclude the possibility of the presence of a nucleus.

An endeavour to account for the absence of a nucleus in the blood corpuscle of the human adult has been made by supposing that it does really exist in the blood of the embryo. The answer to this supposition is, that no nucleus is to be found in embryonic blood, and that if it were, it would be no reason why the nucleus should not also be met with in the blood of the adult, seeing that the blood disc is not a permanent structure, as an eye or a limb, but one which is perpetually subject to destruction and renewal.

Having then arrived at the conclusion that no nucleus exists in the blood corpuscle of man, we have now to ask ourselves the question, what, then, is really the constitution of the red blood globule?

Some observers have compared it to a vesicle. This definition does not seem to be altogether satisfactory; for although each corpuscle possesses the endosmotic properties common to a vesicle, no membrane, apart from the general substance of the globule, (I speak more particularly of the human blood disc,) has been demonstrated as belonsinar to it.


  • Among those who have asserted their belief in the presence of a nucleus, maybe mentioned Hewson, Miiller, Gerber, Mandl, Barry, Wagner, Rees, Lane, and

Addison ; and of those who have held a contrary opinion, Magendie, Hodgkin, Liston, Young, Quekett, Gulliver, Lambotte, Owen, and Donne.



Each globule in man may therefore be defined to be an organism of a definite form and homogeneous structure, composed chiefly of the proteine compound globuline, which resembles albumen very closely in its properties ; its substance externally being more dense than internally, it being endowed with great plastic properties, and, finally, being the seat of the colouring matter of the blood.

The extent to which the red globule is capable of altering its form, is truly remarkable. If it be observed during circulation, it will be seen to undergo an endless variety of shapes, by which it accommodates itself to the space through which it has to traverse, and to the pressure of the surrounding globules. The form thus impressed upon it is not, however, permanent; for as soon as the pressure is removed, it again instantaneously resumes its normal proportions. On the field of the microscope, however, the corpuscles may be so far put out of form, as to be incapable of restoration to their original shape.

Some observers have assigned to the red globule a compound cellular structure, comparing it to a mulberry. It need scarcely be said that such a structure does not really belong to it. A puckered or irregular outline is not unfrequently presented by many globules; this is due sometimes to evaporation, and then arises from the presence around the margin of the disc, and occasionally over the whole surface, of minute bubbles of air;* and at other times it is the result of commencing decomposition, or the application of some special reagent, as a solution of salt, in which cases a true change in the form, but not in the structure of the globule, does really occur; its outline becomes irregular, and the surface presents numerous short and obtuse points or spines.f Globules in this state bear some resemblance to the pollen granules of the order Compositce.X (See Plate I- fig. 5.)

  • This vesiculated appearance of the blood corpuscles may be produced at once

by pressure.

f Mr. Wharton Jones says, " the granulated appearance " seems to be owing to a contraction of the inner and a wrinkling of the outer of the two layers of wnich he conceives the wall of the corpuscle to be formed.

I The opinions promulgated by some observers in reference to the intimate structure of the blood corpuscles are singular, and are rendered interesting mainly by reason of the ingenuity of the views expressed. Mr. Addison remarks: 1 "Blood

1 Experimental Researches, pp. 236, 237. Transactions of Prov. Med. and Surg. Association.


Colour. — The hcematine, or colouring matter of the blood, seems in the red corpuscle of the mammalia to be diffused generally throughout its substance; in the oviparous vertebrata, however, it is confined to that portion of each corpuscle which corresponds with

corpuscles, therefore, appear to consist of two elastic vesicles, one within the other, and to possess the following structure: 1st, an external and highly-elastic tunic, forming the outer vesicle; 2d, an inner elastic tunic, forming the interior vesicle; 3d, a coloured matter, occupying the space between the two tunics; and 4th, a peculiar matter, forming the central portion of the corpuscle." Mr. Wharton Jones l ascribes a somewhat similar constitution to the blood corpuscle : " The thick wall of red corpuscle," he says, "consists of two layers. The outer is transparent, colourless, structureless, and resisting, and constitutes about one-half of the whole thickness of the wall. The inner layer is softer and less resisting; and is that which is the seat of the colouring matter." Dr. G. O. Rees and Mr. Lane 2 describe the blood corpules as containing a fluid, and provided with a nucleus composed of a thin and colourless substance. The views of Dr. Martin Barry are, however, the most peculiar of any ever yet published in reference to the blood corpuscle; when first they were announced in the pages of the Philosophical Transactions, the scientific world were taken by surprise and wonderment. Microscopes, which had long been suffered to remain undisturbed on their shelves, were immediately had recourse to, and many scientific men, who previously had never employed the instrument in their investigations, were induced to procure it, in order that they might themselves bear ocular witness of the astonishing facts related by Dr. Barry in reference to blood corpuscles. A short abstract of Dr. Barry's views will be read by some with interest. Dr. Barry considers that the molecules, the red corpuscles, and the white globules, are different states of the development of the same structure, the true blood globule. (This is also the opinion of Addison and Donne.) The first he denominates a "disc," and the last a "parent cell." These different stages in the development of the blood globule, Dr. Barry compares with similar conditions of the germinal vesicle of the ovum. "The disc," he says, "is the most primitive object we are acquainted with;" that it is synonymous with the "nucleus" of most authors, and the "basinshaped granules" of Vogel ; that it " contains a cavity, or depression," " the nucleolus," which " is the situation of the future orifice," which he says the blood corpuscle in certain states exhibits, and "by means of which there is a communication between the exterior of the corpuscle and the cavity in its nucleus ;" lastly, the disc is regenerated by fissiparous divisions. These discs are also denominated, " primitive discs," "foundations of future cells." The "parent cells" he conceives to be made up of an assemblage of these discs. Again, Dr. Barry states, " The nuclei of the blood corpuscles furnish themselves with cilia, revolve, and perform locomotion;" "the primitive discs exhibit an inherent contractile power." And of the corpuscles themselves, he remarks, " Molecular motions are discernible within the corpuscles of the blood," — " changes of form are observed under peculiar circumstances in the corpuscles of the blood." These are, however, only the beginning of wonders related. Dr. Barry elsewhere goes on to observe : " In the mature blood corpuscle (red blood the blood disc of the mammiferous vertebrata, viz: the outer or capsular portion of it — the nucleus which alone exists in the blood corpuscles of birds, fishes, and reptiles, being entirely destitute of colouring matter.

1 See British and Foreign Medical Review, No. xxvni. 2 Guy's Hospital Reports, 1840.



The colour of the blood, it has long been believed, is intimately disc), there is often to be seen a flat filament or band already formed within the corpuscle. In Mammalia, including man, this filament is frequently annular; sometimes the ring is divided at a certain part, and sometimes one extremity over-laps the other. In birds and amphibia the filament is of such length as to be coiled. This filament is formed of the discs contained within the blood corpuscle. . . "The filament thus formed within the blood corpuscle has a structure which is very remarkable. It is not only flat, but deeply grooved on both surfaces," in an oblique manner. "It is deserving of notice," continues Dr. Barry, "that in the first place, portions of coagulum of blood sometimes consist of filaments having a structure identical with that of the filaments formed within the blood corpuscle; secondly, that in the coagulum I have noticed the ring formed in the blood corpuscle of man, and the coil formed in that of birds and reptiles, unwinding themselves into the straight and often parallel filaments of the coagulum, changes which may be seen also taking place in blood placed under the microscope before coagulation; thirdly, that I have noticed similar coils strewn through the field of view when examining various tissues, the coils here also appearing to be altered blood corpuscles and unwinding; lastly, that filaments having the same structure as the foregoing, are to be met with apparently in every tissue of the body." These filaments Dr. Barry conceives finally to constitute "fibre," whenever this elementary structure is encountered.

These multiplied and extraordinary observations of Dr. Barry, it is now necessary to observe, remain unconfirmed in all the most essential particulars up to the present time. Shortly after their promulgation, Dr. Griffiths, 1 and Mr. Wharton Jones, 2 objected to the statement of Dr. Barry, that there exists in the blood corpuscle a primordial fibre, observing that the appearances relied upon were due to decomposition. In connexion with the subject of fibre in the blood globules, the analogy referred to by Dr. Willshire, 3 between a dark line observed in the starch vesicle, and Dr. Barry's alleged fibre, may be noticed, as well as the affirmations of Dr. Carpenter, 4 that Dr. Barry had shown him, among corpuscles of the blood of the newt, preserved in its own serum, many of a flask-like figure, and which might be compared to a pair of bellows, and the projecting portion of which appeared to Dr. Carpenter to be a filament having a much higher refracting power than the general substance of the corpuscle. Dr. Barry also showed Dr. Carpenter, in blood preserved in corrosive sublimate, a corpuscle which was evidently destitute of the ordinary nucleus, and which contained what appeared to be a filament, presenting transverse oblique markings which resembled those of the fibrillfe of a muscle. The observations of Dr. Barry, and the confirmatory statements of Dr. Carpenter, will at least be possessed of historical interest, if any real and intrinsic importance be denied to them. The views of Dr. Barry are given at length in the Philosophical Transactions for 1840 — 1843.

l Annals of Natural History February, 1843. 2 Transactions of the Royal Society, December, 1842. 3 Annals of Natural History, 1843. 4 Annals of Natural History, 1842.



connected with the presence of iron in the blood corpuscles : from the fact, however, that iron exists in the chyle,* and in the colourless blood of certain animals,f it is clear that the mere presence of iron is not in itself sufficient to account for the colour of the blood ; this depends most probably upon the state of combination of the iron in the blood. Liebig states, as will be shown immediately, that the iron in the blood exists in the varying conditions of peroxide, protoxide, and corbonate of the protoxide of iron.

USES OF THE RED CORPUSCLES.

In connexion with Respiration. — Observation has taught us the fact that the colour of the blood changes considerably, according as it is exposed to the influence of oxygen and carbonic acid gases ; it becoming bright red under the influence of the former, and dark red, almost black, under that of the latter gas.

Now, the microscope has revealed to us the additional fact that the colouring matter of the blood resides within the red corpuscles ; and hence we are led to infer that the changes of colour alluded to are accompanied by alterations in the condition of the colouring matter contained in those corpuscles.

Further, the alterations of colour which have been mentioned take place not only in blood withdrawn from the system, but also in that which still circulates in the living body, the vital fluid being exposed in the lungs to the influence of the oxygen contained in the atmosphere, and to carbonic acid in the capillary system of vessels.

But it is not merely a change of colour which the blood undergoes, or rather the coloured blood corpuscles undergo, on exposure to either of the gases particularized, but they also experience at the same time, as might easily be inferred, a positive change of condition, a portion of one or other of the gases to which the blood corpuscles are exposed being imbibed by them.

That it is really the red corpuscles which absorb the oxygen, or the carbonic acid, as the case may be, admits of demonstration, and is proved by the fact that these gases lose but little volume when placed in contact with the liquor sanguinis, or serum of the blood.

  • See article " Lymphatic System," by Mr. Lane. Encyclopardia of Anatomy and

Physiology, April, 1841.

f "The Blood Corpuscle considered in its different Phases of Development in the Animal Series," by J. W. Jones, F. R. S. Transactions of the Royal Society, part ii. for 1846.


It is clear, then, that the coloured corpuscles are the seat in which these changes occur. Again, from the fact that the blood becomes bright red or arterial on exposure to oxygen, as in the lungs, and dark red or venous on being submitted to the action of carbonic acid, as in the capillaries, it has been inferred that they are, first, carriers of oxygen from the lungs to all parts of the system, and, second, vehicles for the conveyance of carbon back again to the lungs.

This inference is correct as far as it goes, but it fails to explain why the imbibition of oxygen or carbonic acid gases should be accompanied by changes in the colour of the blood ; and it also fails to show why those gases themselves should be imbibed.

From the constant presence of iron in the coloured blood corpuscles, it has been inferred that this is the base with which the oxygen and the carbonic acid gases combine, but the exact nature of the combinations thus formed it was reserved for the illustrious Liebig to make known.

Liebig declares that, in arterial blood, the iron is in the state of a peroxide, and in venous blood in the condition of a carbonate of the protoxide.

To this conclusion Liebig has arrived by observing the manner in which the above-mentioned compounds of iron comport themselves when not in connexion with the blood, but when exposed to the same influences as the blood itself is subjected to.

Thus, he says, " The compounds of the protoxide of iron possess the property of depriving other oxydised compounds of oxygen, while the compounds of peroxide of iron under other circumstances give up oxygen with the greatest facility."

Again, " Hydrated peroxide of iron, in contact with organic matters destitute of sulphur, is converted into carbonate of the protoxide."

Lastly, "Carbonate of protoxide of iron in contact with water and oxygen is decomposed, all the carbonic acid is given off, and by absorption of oxygen it passes into the hydrated peroxide, and which may again be converted into a compound of the protoxide."

Now, the above-described changes, which the compounds of iron when exposed to the same influences as the blood corpuscles are themselves submitted to, precisely correspond with those alterations which it is known and ascertained that the blood corpuscles do themselves experience, and therefore there is every probability in favour of the strict accuracy of Liebig's explanation of the chemical changes which the blood corpuscles pass through during respiration and circulation.

Thus, it has been long known, that in the lungs the coloured blood corpuscles give off carbonic acid, and imbibe oxygen: and it has also been ascertained that during their circulation they lose a portion of their oxygen, and acquire carbon.

Venous blood, then, exposed to the air, gives out carbonic acid, and absorbs oxygen; but arterial blood, submitted to the same influence, gives out oxygen, and acquires carbonic acid; the seat of these changes being the red corpuscles.

It will be seen, on reflection, that, according to the views just propounded, the surplus amount of oxygen which exists in the peroxide, becomes disengaged in the reduction of that oxide to the state of protoxide: during circulation in the capillaries, this surplus is chiefly expended in the elaboration of the different secretions which are continually being formed in the various organs of the body.

Such is the corpuscular theory of respiration. Hereafter we shall have to speak of a corpuscular theory of nutrition, growth, and secretion.

In connexion with Secretion. — It is very probable that the use of the red corpuscles is not limited to the mere office of carrying oxygen from the lungs to be distributed to all parts of the system, and of carbon back again to the lungs to be eliminated, but that they have an ulterior and additional function to discharge. Thus, some observers suppose that they exert some influence over the constitution of the blood itself, elaborating, from the materials continually thrown into it by the tho^ racic duct, a further quantity of fibrin. There is more reason to believe, however, that it is the white corpuscles which are principally concerned in this process of elaboration, seeing that their structure agrees with that which is generally possessed by true secreting cells. I therefore myself would be inclined to attribute to the red corpuscles but little influence over the constitution of the blood.

It may be stated that both Wagner* and Henle are of opinion that the red corpuscles are connected with secretion, and the latter, in his "General Anatomy," calls them " swimming glandular cells."

Effects of Reagents.

The blood globules are much modified by tne application of numerous reagents, and which, therefore, may be employed with advantage in their investigation.

  • Physiology, by Willis, part ii. p. 448.

Serum. — It has already been observed that, in the serum of the blood, their natural element, the globules preserve unaltered, for a time, their normal form.

Water. — The application of water causes the globules almost immediately to lose their flattened and discoidal character, the depressions on their surface are effaced, and they become spherical. This change in the form of the corpuscles is necessarily accompanied by a diminution of their size. (See Plate I. jig. 3.)

Spirits of Wine, JEther, Creosote. — The same results follow the use of a variety of liquids, as spirits of wine, aether and creosote. These agents, however, in addition, render the globules exceedingly diaphanous, so much so indeed as that they are often with difficulty to be discovered. In the globules rendered thus transparent, no traces of granular contents can be detected.

Acetic acid. — This preparation first deprives the globules of their colouring matter, thus rendering them exceedingly transparent, and subsequently dissolves the human blood corpuscle, without residue, but not that of a frog, &c, the nucleus of which remains entire. (See Plate II. fig. 5.)

Ammonia. — This alkali acts in a similar manner.

Nitric Acid, Muriate of Soda. — These reagents contract the globules, and render their outline more distinct.

Iodine. — This likewise renders the outlines more distinct, without at the same time deforming and otherwise altering the globules.

Corrosive Sublimate. — In a strong solution of this liquid, the outlines of the globules are more defined, and the globules may be preserved for examination for a considerable length of time.

We shall next pass to the consideration of the white globules, and show in what particulars of form and structure they differ from the red.

WHITE GLOBULES.

The white globules of the blood are by far less numerous than the red; they nevertheless are more abundant than a superficial observer would suppose : this arises from the fact that many of them are concealed from view on the field of the microscope by the red globules, which so greatly outnumber them. The white corpuscles differ from the red in several particulars : in size, in colour, in form, in structure, in their properties, and doubtless also in their uses.*

  • Spallanzani was the first to notice the existence of two forms of globules in the

blood of salamanders; Miiller verified their presence in that of the frog, and M. Mandl detected them in man and mammalia.

Size. — In man and the mammalia the white globules are generally larger than the red : like those, also, their dimensions vary very considerably in the blood of the same individual abstracted at any given time, and even to an extent still greater. Their average size, when contained in the serum of the blood, may, however, be estimated at about the ^jVo °f an inch* (see Plate I. fig. 1) : when immersed in water, however, they swell up, and increase very considerably in size, in this liquid sometimes measuring the T J~ of an inch. (See Plate I. fig. 6.) In the blood of reptiles, especially in that of the frog, a contrary relation between the size of the red and white globules exists ; the latter in these, instead of being larger than the red corpuscles, are two or even three times smaller. This fact it is important to bear in mind, in considering the question of the transformation of the white globules into red.

Form. — Instead of being of a flattened and disc-like form, as are the red globules, the shape of the white corpuscle, when free, is in all classes of the animal kingdom globular. This particular likewise throws much light upon the disputed point as to whether the white globules become ultimately converted into red corpuscles, and which we shall have to treat of more fully hereafter.

Like the red corpuscles, however, although to a less remarkable extent, the white globules, when subject to pressure, undergo a change of form : this change is frequently well seen when viewing the circulation of the blood in the capillaries, the white corpuscles often becoming compressed between the walls of the vessels and the current of red blood discs, and by which compression they are made to assume elongated and oval forms ; like the red corpuscles, also, they immediately regain their normal form, the pressure being removed.


  • Mr. Gulliver gives the 2T0 „- °f an i nen as the average measurement of the human

colourless blood corpuscle.


Structure. — In almost every relation which can be named, the white globules would appear to be the antagonists of the red; for, instead of being of a homogeneous texture, they are of a granular structure throughout, each full-sized white globule being constituted of not less than from twenty to thirty distinct granules, the presence of which imparts to it a somewhat broken outline: these granules are often seen, especially after the addition of water, and some other reagents, to be in a state of the greatest activity in the interior of the corpuscles. It is only in the blood globule of mammalia, however, that we find this antagonism to prevail. The blood corpuscle of the

frog, and doubtless of other reptiles, as well as birds and fishes, is 

assuredly a compound structure, the investing or transparent part of each being in no way, as regards structure, distinguishable from the substance of the human blood disc, and the nucleus also being identical in composition, though not in origin, with the white globules of the blood, not merely of mammalia, but likewise of reptiles, birds, and fishes. (See Plate II. fig. 5.) The form of the nucleus, in the frog, &c, corresponds with that of the globule; that is, it is elliptical (see Plate II. fig. 2) : water, however, affects the nucleus, as first observed by Mandl, in the same way as it acts upon the corpuscle itself, rendering both perfectly spherical. (See Plate W.figs. 3 and 4.) If to globules in this condition acetic acid be added, the capsule will be dissolved, leaving intact the nucleus, between which and a white globule I have not been able to detect, although using an instrument of the very best description, the slghtest structural difference: a difference does certainly exist, but it is one of size, and not of structure, the nucleus being three or four times smaller than a white globule of ordinary dimensions. (See Plate 11. fig. 5, and Plate II. fig. 1.) This identity of organization between the white globule and the nucleus of the blood disc of the frog, furnishes the strongest evidence with which I am acquainted of the convertibility of the white globules into red, evidence which, nevertheless, I regard as wholly inadequate to demonstrate the reality of the conversion.

Nucleus. — The white corpuscles, under some circumstances, would appear to be nucleated ; thus nuclei are evident in corpuscles which have been immersed in water, or even in serum, for any length of time, although they are not usually seen in those of that fluid immediately after its abstraction from the system. I am inclined to regard their formation as resulting partly from the operation of endosmosis, whereby a portion of the contents of each corpuscle becomes condensed in the centre.

The nucleus occupies sometimes the entire of the interior of the corpuscle, a narrow and colourless border destitute of granules, alone indicating the extent of the corpuscle; generally, however, it is about the one-third of its size, and is more frequently eccentric than centric. It is usually darker than the rest of the corpuscle, and would appear to contain a greater number of molecules. (See Plate I. fig. 6.) Sometimes it presents to the eye of the observer the appearance of an aperture; this appearance, although very striking, is most probably fallacious.


Mr. Addison regards the nucleus presented by the white corpuscles as primary, an opinion in which I concur.

Properties. — The white corpuscles of the blood differ not less in their properties from the red than they do in form and structure: thus, acetic acid, which dissolves the latter, contracts somewhat the former, and renders the contained granules more distinct; in water, the red globules become globular and smaller in size, while the white increase considerably in dimensions in the same liquid (see Plate I. fig. 6), and finally burst in it, their molecular contents escaping. In liquor potasses, both the red and white corpuscles are destroyed and dissolved ; previous to which, however, in the white globules, some interesting changes are seen to take place ; immediately on the application of the alkali, the molecules contained in their interior are observed to be in active motion, and in a short time the corpuscles burst open, or explode, discharging numerous granules, amounting sometimes to thirty or forty; and which, together with the transparent matter of the corpuscles, finally becomes dissolved. — "Frequently, when the liquor potassee is acting with diminished energy, the cor-» puscles give a sudden jerk, and in a moment enlarge to double or three times their former size, without losing their circular outline: the molecules and granules within them are more widely separated from each other, but not dispersed; and they are seen held together, or attached to the tunic of the corpuscle, by delicate connecting filaments. This singular and instructive change does not, of course, last long; the alkali, continuing its action, ruptures the tunic of the corpuscle, dispersing and dissolving its contents." — Addison.

When examined in the living capillary vessels, they are seen to manifest different properties to the red, and also to have a very different distribution in those vessels. Thus, the white corpuscles frequently adhere to the inner wall of the capillaries, which the red rarely do ; and while the red globules, in circulating, occupy the centre of each vessel, the white corpuscles are placed between this and the walls of the vessel.

A difference may also be observed in the relative speed with which the two kinds of corpuscles circulate, the red flowing onwards with greater rapidity than the white. The forces which determine the circulation in the vessels would appear to act only on the red corpuscles, the motion of the white globules being entirely of a secondary and indirect character, it being communicated to them by the edge of the current in the axis of which the red corpuscles move, in the same way as the stones at the bottom of a stream are rolled over and borne onwards by the superincumbent water.

The cause of the slower motion of the white corpuscles in the capillaries may be thus explained. A greatly retarded motion of the fluid circulating in any vessel or channel is always observed towards the periphral border of the current. This retardation would appear to arise from the resistance which the circulating fluid encounters by coming in contact with the walls of the vessel or sides of the channel through which it flows.

In what way, however, is the difference in the position in the vessels occupied by the red and white corpuscles to be explained? whv do the former always circulate in the axis of the vessel, while the latter are constantly placed outside this ? and what is the inference to be deduced from this difference in their situation ?

The red corpuscles, as we know, are flattened discs, constituted of an elastic and yielding material; and the white, on the contrary, are globular bodies of a more dense composition and of but little elasticity.

  • Now, it is very probable that the peculiar form and properties possessed by the coloured corpuscles of the blood may result in such an

adaptation and arrangement of them, the one with the other, that a physical impossibility is presented to their indiscriminate admixture and circulation in the same vessel with the white corpuscles.

But there are other facts which will serve to explain the difference of position: Thus, the red corpuscles have an attraction for each other, as is manifested on the field of the microscope by the formation of the strings of corpuscles already referred to, where also it is seen that they have no such affinity for the white corpuscles, which usually lie detached and isolated from the red. On the other hand, however, the white, as before stated, have an attraction for the walls of the vessels through which they pass, and which is declared by their frequent adhesion thereto.

The question may be asked, have these attractions any thing to do with electric conditions? All the inquiries which have been undertaken, with the view of proving that the blood is possessed of electric properties, have hitherto signally failed to demonstrate the existence of any.

Lastly, what inference is to be deduced from the different positions occupied by the two kinds of blood corpuscles, and from the different rates of their circulation in the capillaries ?

The rapid passage of the red corpuscles through the capillaries, together with their central situation, would lead the observer to infer that they had but little direct relation with the parts outside those capillaries; that the office discharged by them was one of distribution ; whereas the slow progress of the white corpuscles through the capillary vessels, as well as their peripheral position, would lead to the conclusion that a close relation existed between them and the parts adjacent and external to the vessels. Now, these deductions are precisely those which other facts and observations tend to confirm and establish, as we have already seen in reference to the red corpuscles, and as we shall immediately proceed to show in relation to the white globules.

While viewing the capillary circulation, it is easy to convince oneself that no contraction of the parietes of the capillaries occurs, and that, therefore, the motion of the blood is independent of any action of those vessels themselves, on their contents.

USES OF THE WHITE CORPUSCLES.

The uses of the white corpuscles have not as yet oeen fully determined; enough, however, of their nature has been ascertained to show that they are closely connected with the functions of Nutrition and Secretion. We shall here invert the natural order in which the description of these subjects should be entered upon, and speak first of secretion.

Uses in connexion with Secretion. — It would appear that, for the most part, secretions are formed in cells : the correctness of this statement is, in some degree, proved by the fact that the lower classes of the vegetable kingdom are entirely constituted of cellular tissue.

It is also further supported by the fact, that the essential structure of all glands in the animal frame is that of cells.

It would appear, also, that the cells, entering into the composition of a single organ, have the power of producing more than one kind of secretion. This is witnessed in the petals of many flowers, the cells of which frequently elaborate fluids of several distinct colours.

There is much reason to believe, that the granules, which are so constantly associated with the cells, are the active agents engaged in the production of the secretion, the exact constitution of these granules determining the character of the secreted product.

Now, in the white corpuscles of the blood we have precisely the same granular constitution which is seen to belong to cells which are indisputably engaged in the process of secretion.


From the observation of these and other facts, Mr. Addison has been led to entertain the opinion, that the white corpuscles of the blood "are very highly organized cells, from which the special tissues and the secretions are elaborated."* In continuation of this subject, Mr. Addison goes on to remark : "And it appears that the renovation of these tissues and secretions from the blood does not take place by the cells discharging their contents into the general mass of the circulating current, to be separated therefrom by some peculiar transcendental and purely hypothetical selective process of exudation, through a structureless and transparent tissue, but by being themselves attached to, incorporated with, and performing their special function in the structure."

Thus, Mr. Addison conceives that the fibrillating liquor sanguinis is formed and elaborated in the white corpuscles of the blood, and that it never exists in that fluid in a free state, and that its presence in the crassamentum, and especially in that part of it which constitutes the buffy coat, arises from the rupture and destruction of the white corpuscles, and the escape of their contents. This opinion he supports by a series of ingenious experiments, one of which may here be referred to. The tenacious property belonging to mucus is well known, in which respect, as well as in the smaller number of globules, similar to the white corpuscles of the blood contained in it, it differs mainly from pus. Now, by the addition of a drop of liquor potasses to a little pus, which was previously white and opaque, and in which the presence of a considerable number of white corpuscles was ascertained by means of the microscope, its appearance underwent a complete change, the pus became transparent and tenacious, presenting precisely the characters of mucus. The fluid being again examined microscopically, it was found that most of the globules were ruptured and dissolved, and that the liquid portion of it fibrillated in the same way as that of mucus, and that of the liquor sanguinis ; from this and other analogous experiments Mr. Addison formed the conclusion, that the fibrillating liquor sanguinis was derived from the white corpuscles, and that it does not exist in the blood in a free condition.

According to Mr. Addison, the secretions, "milk, mucus, and bile, are the visible fluid results of the final dissolution of the cells." Hence, therefore, a secretion is the result of the last stage of the process of nutrition. And, again, "If, therefore, the colourless blood corpuscles be termed "parent cells," they must be considered as pregnant with the embryo materials of the tissues and secretions, and not with "young blood cells."

  • "Experimental Researches," Transactions of Prox. Med. and Surg. Association,

vol. xii. p. 260

It is scarcely necessary to observe that these highly ingenious views of Mr. Addison are by no means established. That the cells of glands and their contained granules are intimately connected with secretion, there are many facts to prove ; but that the white corpuscles of the blood are, in the animal economy, the special organs of secretion, and also that the secretions said to be elaborated by them, escape from them, not by transudation through their membranes, but are set free by the entire and final dissolution of the corpuscles, are views which cannot be safely adopted until much additional evidence is adduced in support of them.

The opinion entertained by Dr. Barry, that the colourless corpuscles are "parent cells," seems to me to be purely hypothetical.

Let us now bestow a few reflections upon Nutrition :

Uses in connexion with Nutrition. — That the white corpuscles are concerned in the process of nutrition, there is more evidence to show than there is in favour of their connexion with that of secretion. The question to be solved, however, is, in what way do these corpuscles administer to nutrition ? do they contribute to nutrition and growth, by their direct apposition to and incorporation with the different tissues of organs? This is the opinion of Mr. Addison, who says of them, that they are the "foundations of the tissues and the special secreting cells, the link between the blood and the more solid structures, the unity from which the pluralities arise."

Dr. Martin Barry also adopts the notion that tissues are formed by the direct apposition of the blood corpuscles. Dr. Barry makes no exact distinction between the red and the colourless globules; but from the fact of his calling the latter "parent cells" filled with "young blood discs," it would appear that he considered that the red corpuscles gave origin to the different structures of the body by their direct union and incorporation with each other. This view is far less tenable than that of Mr. Addison, and neither is supported by a sufficient number of facts to render its accuracy any thing but exceedingly problematical.

That the white corpuscles of the blood are engaged in the process of nutrition is proved by the fact, that they are found in increased quantities in vessels which are actively administering to that function. This accumulation is witnessed also in the capillary vessels of any parts which are subjected to irritation of any sort, and in which, as a consequence of that irritation, there is augmented action.

The gradual collection of the white corpuscles of the blood in the capillary vascular net-work, may be seen to the greatest possible advantage in the tongue of the frog, as also in the web of the foot of that coveniently-formed creature, as the result of continued exposure of the parts to the action of air.*

But it is not alone the aggregation of the colourless corpuscles that may be seen in the minute vessels ; their escape from those vessels may likewise be determined by a prolonged examination of them. If, after the continuance of this congested condition of the vessels for twenty-four or thirty-six hours, they are again examined, it will be obvious that certain of the corpuscles have become entangled in the fibres which form the walls of the vessels, and that certain others have altogether passed the boundaries of the vessels, and now lie external to them.

Again, it is asserted, that the epithelial cells are derived from the white corpuscles of the blood. If this be correct, it would appear that the escape of these corpuscles is a perfectly normal and natural occurrence.

Thus far, then, the endeavour to prove the transformation of the colourless corpuscles of the blood into tissue cells, would appear to be successful; but it is here the chain of evidence breaks; and beyond the fact, which is by no means established, of their constituting epithelial cells, we have no further proof to adduce of their structural incorporation with the living tissues. Of this occurrence it would, of course, be difficult to procure satisfactory demonstration, on account of the opacity of the parts on which our examination would have to be conducted. It may be remarked, however, that, if founded in fact, we should expect to find a greater correspondence in the size and form, &c, of the elementary tissues, with that of the corpuscles from which, according to some observers, those tissues are derived. f

The corpuscular theory of nutrition, then, proposed by Mr. Addison,

  • Mr. Addison states that, in order to insure a satisfactory exhibition of this

important and curious phenomenon, the parts should be irritated in some manner, as by immersion for a minute or two in warm water at a temperature of 95° Fahrenheit, or by permitting a few. crystals of common salt to dissolve upon it. These methods I have tried, and have found that they have usually resulted in the entire cessation of the circulation in the capillaries, and this has been also the case even when a weak solution of salt in water has been applied.

f The cells of the liver and spleen resemble closely in appearance the white corpuscles of the blood ; between them, however, well-marked differences exist, so that it is by no means to be inferred that the former are derived directly from the latter.


in the present state of our knowledge, can only be sustained by having recourse to a certain amount of theoretical reasoning or to particular assumptions.

The fact, however, still remains to us, that the white corpuscles are concerned in nutrition, although the precise manner in which they are so is still open to investigation, and this fact is strengthened and confirmed by the phenomena of disease. Thus, there is much evidence to show that, wherever nutrition is impeded, the colourless corpuscles accumulate in increased quantities in the vessels; and it is by this accumulation, also, that we are enabled to account for the critical abscesses and discharges which characterize some affections, and to recognise the importance which ought to be attached to their occurrence.

That the colourless corpuscles are really present in increased numbers in the blood, in disease, is attested by the evidence of numerous observers: thus, Gulliver,* Davy,f and Ancell,J have observed them in unusual quantities in inflammatory affections, and especially in such as are attended with suppuration. Mr. Siddall and Mr. Gulliver have repeatedly observed them in vast numbers in the horse, especially when the animal has been suffering from influenza. Donne has likewise recognised their presence in increased quantities in disease; and Mr. Addison finds them to abound in the hard and red bases of boils and pimples, and in the skin in scarlatina and in most cutaneous affections.

Several processes may have been pointed out by which the white globules may be separated from the red, and thus be brought in a manner more satisfactory under view. 1st. Acetic acid dissolves the red corpuscles, leaving the white almost unchanged. 2d. A drop of water, floated gently across a piecs of glass, on which a small quantity of blood has been placed, will remove the red corpuscles, the white remaining adherent to the surface of the glass. This ingenious method was, I believe, first indicated by Mandl. 3d. The third process depends for its success upon the defibrination of the blood by whipping, and which has already been alluded to. If blood thus defibrinated be set aside for a time, the red globules will subside to the bottom of the containing vessel, forming one stratum, and the serum will float upon the top, constituting a second layer ; but between these two layers a third exists; this is very thin, and is formed by the white globules, which may be reached after the removal of the serum by means of a siphon.* Donne points out this method in his excellent "Cours de Microscopic" 4th. A fourth means of procuring the white globules is described by Mr. Addison. If a portion of fluid fibrin be removed from beneath the pellicle which is first formed over the clot, it will be found to contain numerous white globules.

  • Appendix to Gerber's General Anatomy, p. 20.

f Researches, Phys. and Anal., vol. ii. p. 212.

I Lectures in the Lancet, 1839-40, vol. ii. p. 777.



The observer, having satisfied himself of the accuracy of the various facts brought under his notice, in the next place will be prepared to enter into the important questions as to the origin and destination of the globules of the blood. We will consider first the origin of the white globules.

ORIGIN OF THE GLOBULES OF THE BLOOD.

The origin and end of the blood globules ! Whence do they come, and whither do they go ? These are questions of the highest importance ; and it could be wished that the replies to them were of a more satisfactory and definite nature than those which we are about to make will, it is feared, be considered.

Origin of the White Globules. — Various opinions have been entertained in reference to the nature and origin of the white corpuscles of the blood, the principal of which we will now proceed to notice.

One of the earliest notions formed respecting the white corpuscles was that of Hewson, who believed that they were to be considered as the nuclei of the red blood corpuscles, and hence he denominated them "central particles:" to this conclusion Hewson was doubtless led by observing the great and remarkable resemblance which exists between the nuclei of the blood globules of certain animals and the white corpuscles themselves.

Two facts, however, are known, which satisfactorily prove that the denomination of central particles is not applicable to the white corpuscles, and that they do not form the nuclei of the red blood discs; the first of these is, that no nuclei exist in the true blood globules of the entire class of mammalia in which white corpuscles are abundantly encountered, and the second is the great difference in size observed between the nuclei and the white corpuscles in those animals in which the two organisms exist together in the blood.

  • The position occupied in this case by the white corpuscles shows that they are

of lighter specific gravity than the red, a reference to which fact will also account for their presence, in such quantities, in the bufiy coat of the blood, and will likewise explain the reason why they first come into focus when mixed with the red globules in a drop of water.



An opinion somewhat similar to the above has been held by some observers, viz: that the white corpuscles are to be regarded as the "escaped nuclei" of the red blood corpuscles. The facts adduced to disprove the former notion respecting them, are likewise sufficient to show the fallacy of that just referred to.

By Dr. Martin Barry the white corpuscles are considered to be the last stage of the development of the red blood disc, and he has assigned to them the designation of "parent cells," under the impression that the granules, of which many are contained in each corpuscle, become developed into new blood discs; this idea of Dr. Barry is purely hypothetical, and its accuracy is but little probable.

Mr. Addison also believes that the white corpuscles represent an advanced condition of the growth of the red blood disc, but he differs from Dr. Barry, however, in not considering them to be parent cells, filled with young embryos, designating the white corpuscles "tissue cells," under the belief that they become incorporated with, and constitute an integral portion of the solid structures of our frame- work. The value of this theory has already been discussed.

Mandl denominates the white corpuscles "fibrinous globules," and he conceives that the nuclei, which he states belong to all red corpuscles of the blood, as well as the white globules, are not primary formations, but secondary; that these structures do not exist in the blood while circulating within the body, but that they are formed after its abstraction therefrom; and M. Mandl further states, that the steps of the formation of the white globules may be witnessed on the port object of the microscope. That this view is incorrect, not the shadow of doubt can be entertained. The regular form and size of the white globules, their presence in the blood the moment after their abstraction from the system, but especially the fact that they may be seen in vast quantities in that fluid while still circulating in the capillaries, all negative the idea of the formation of the white globules out of the system, in obedience to a mere physical law.

Mr. Wharton Jones, in a recent communication made to the Royal Society, has bestowed upon the white corpuscles the appellation of "granule cells," and that gentleman considers them to represent an early stage in the development of the red blood globule. The peculiar views entertained by Mr. Jones will, however, be referred to more fully under the head of the origin of the red blood disc.


The white corpuscles are also synonymous with the "exudation corpuscles" of many writers, and especially of Gerber, who has under this denomination assigned to them a false value ; the presence of the white corpuscles in the plastic fluid of exudations being rather accidental than essential.

We come now to refer to the opinion entertained respecting the white corpuscles by Muller, who denominated them " lymph corpuscles," conceiving them to be identical with the granular corpuscles encountered in the lymphatic fluid. Of all the opinions and theories of the nature of the white corpuscles alluded to, that of Muller is probably the only correct one ; Muller, however, was not acquainted with their existence in the blood of mammalia, but merely in that of frogs and other analogous animals.

The opinion that the white corpuscles are red blood globules in process of formation, is one which is maintained by many observers, and nevertheless I regard it as erroneous. In the truth of this view, Wagner, Baly, Gulliver, Professor H. Nasse, and, above all, Donne, are believers. From the excellent work of the latter writer I introduce the following remarks in relation to this point :

"About two hours after injection (with milk), rabbits, dogs, and birds have been opened. I have collected the blood in the different organs, in the lungs, the liver, and the spleen ; every where I have found the blood in the state in which I have described it above, containing a certain number of white globules in all stages of formation, and of red globules more or less perfect : invariably the spleen has presented to me special circumstances so established and so constant that it behooves me to mention them, and especially since they may throw light, at length, upon the true functions of this organ, so long and so vainly sought. I do not dare flatter myself with having completely resolved this problem, and it is but with reserve that I express myself in this particular.

"The blood contained in the large vessels of the spleen offers nothing very remarkable ; but, in expressing that which is enclosed and, as it were, combined with the tissue of this organ, one finds in it a composition well worthy of fixing the attention. In a word, this blood is so rich in white globules, that their number approaches nearly to that of the perfect blood globules ; but, further, the white globules which are there, present in as evident a manner all the degrees of formation an& development, and the examination of this blood does not appear to me to leave any doubt upon the transition which I have pointed out above of white globules to red corpuscles, and upon the successive phases through which the white globules pass to arrive at the state of perfect blood globules. This phenomenon is, above all, striking, after injections of milk, and during the work, which is accomplished in the space of four-and-twenty hours, of the transformation of the immense quantity of milk globules into blood globules. One cannot believe that this is not really the point — the laboratory, if one may so speak — in which this transmutation is effected, and that the spleen is not the true organ of this important function. But I know how like facts, and how the theory which results from them, have need to be confirmed by the researches of other observers, to be definitively adopted with confidence."*

In answer to these observations of M. Donne, I would remark, first, that I have never seen the different stages of formation of the white corpuscles, and of transformation of these into red, described by M. Donne ; and, second, that I believe that he has totally misinterpreted the appearances presented by blood pressed out of the spleen. The cells or corpuscles, of which that organ is itself constituted, so closely resemble the white globules of the blood, that I feel assured that M. Donne has failed to discriminate between the two, and that many of his progressive stages of development are to be referred to the splenic cells or corpuscles, numbers of which are always contained in every drop of blood procured from the spleen.

Having now noticed the various opinions held by different observers in reference to the nature of the white corpuscles, we will next pass to the consideration of their origin or mode of formation. The idea that the white corpuscles are elaborated by the lymphatic glands, has already been referred to ; and, from the absence of these glands in the lower oviparous vertebrata, it is evident that they cannot be regarded as essential to their formation.

It has been stated that, in addition to the white and red globules, numerous smaller particles, termed molecules, exist in the blood. The white globules, in all probability, derive their origin from these molecules, a number of them going to constitute a single white globule. This aggregation of the molecules into masses, or globules, would appear to result from the operation of a general law of the economy, under the influence of which the globules unite with each other, and become invested with a coating, or membrane, probably of an albuminous nature.

  • Cours de Microscopie, pp. 99, 100.


Donne" believes also that he has traced, by direct observation and experiment, the transformation of the minute oily and fatty particles, found in the milk, into white globules. He injected numerous animals, birds, reptiles, and mammalia, with various proportions of milk, and, strange to say, the creatures thus experimented upon experienced no injurious effect beyond a momentary shock, with, however, the single exception of the horse, to which the experiment proved fatal in seven different cases. If, almost immediately after the injection of the milk, a drop of blood be withdrawn from the system at a distance from the point where the milk was introduced, a number of the globules of the milk may be detected quite unaltered, and which may be recognised by their general appearance, their smaller size, and, lastly, by the action of acetic acid, which dissolves the red globules, renders apparent the granular texture of the white, but leaves untouched the molecules of the milk. If the blood be again examined at about the expiration of two hours, the smallest milk globules will be seen to have united themselves with each other by three's and four's, and to have become enveloped, by circulating in the blood, in an albuminous layer, which forms around them a vesicle, analogous to that which surrounds the w T hite globules. The largest remain single, but are equally enveloped in a like covering. These soon break up into granules, in which state the milk globules bear a close resemblance to the white globules of the blood, from which, finally, they are not to be distinguished. " The blood," Donne remarks, "then shows itself very rich in white globules ; but, little by little, these undergo modifications more and more profound; their internal molecules become effaced, and dissolve in the interior of the vesicle, the globule is depressed, and soon it presents a faint yellow colouration : they yet resist better the action of water and acetic acid than the fully-formed blood globules, and it is by this that they are still to be distinguished. At length, after twenty-four hours, or, at latest, after forty-eight, matters have returned to their normal state; no more milk globules are to be found in the blood, the proportion between the white globules and the blood globules, between the imperfect and the perfect globules, has returned to what it is ordinarily: in a word, the direct transformation of the milk globules into blood globules is completed."

In the opinion that the milk globules are convertible into the white globules of the blood, Donne 1 is probably correct, although it must be an inquiry of much delicacy and nicety to determine this point by direct observation. The evidence, however, in favour of his latter position, viz : that the white globules become ultimately converted into red corpuscles, is much more defective, and the facts upon which he relies to sustain this view are open to question, as we have already seen.

The view, then, of the transformation of white corpuscles into red, I consider to be erroneous, and that the white corpuscles, as they differ from the red, in form, structure, and chemical composition, so they also differ in origin; and that the two forms of corpuscles are in every respect distinct, as well in function as in origin.

From the fact of the white corpuscles of the blood being encountered in considerable quantities in the lymph and chyle, which is in truth blood in its primitive form, it is in those fluids, doubtless, that they take their origin, and it is in them that they are best studied.

Origin of the Red Globules. — It has already been shown that Donne and others consider that the red globules are formed out of the, white, which they view as true blood globules which have not reached the last degree of elaboration. Donne sustains this opinion by reference to the following particulars: First, that among the red globules contained in a single drop of blood, all are not affected to the same extent by the use of the same reagent; that some resist its influence for a much longer period than others ; Secondly, he states, that he has observed in some true blood globules traces of a slight punctuation, similar to that which is seen in the white corpuscles; and, Thirdly, in certain white globules he has noticed the compressed form common to the red corpuscles. From the observation of these facts, he draws the conclusion that the white globules are transformed into red blood discs. The first particular alluded to, viz: that the same reagent does not affect equally all the red globules of the same blood, is doubtless to some extent correct, and may be explained by supposing that the red corpuscles are not all of the same age, and therefore are of different degrees of consistence. The remarks as to the granular texture of true blood corpuscles, and the compressed form of certain white globules, it has never happened to me to be able to verify in a single instance; and, for my own part, therefore, I am inclined to allow to them but very little weight in determining the question of the origin of the red corpuscles of the blood. To the views of M. Donne on this point a high degree of plausibility and ingenuity must certainly be accorded ; but in considering this question, not merely the doubtful and even debateable nature of the evidence adduced by M. Donne must be taken into consideration, but also the following fact, viz: that no definite relation exists in the animal kingdom between the size of the red and white globules compared together. In man, and most mammalia, the white globules are larger than the red (see Plate I. fig. 1); in most reptiles, and particularly in the blood of the frog, they are very much smaller (see Plate 11. fig. 1) : from whence it would result that the process adopted by nature for the conversion of the white globules into red, would, in the two classes of the animal creation cited, be of a character wholly different the one from the other. In the first-mentioned, the transmutation would be a work of decrease ; in the second, of increase, or superaddition ; and this supposition, I conceive, would be tantamount to charging nature with the commission of a gross inconsistency.

There are other observers, again, who believe in the formation of the coloured blood corpuscles out of the colourless ones, in a manner totally different from that described by M. Donne.

Thus, Mr. Jones, in a communication recently made to the Royal Society, and entitled "the Blood Corpuscle considered in its different Phases of Development in the Animal Series," states that the blood corpuscle presents throughout the animal kingdom at least two phases of development : in the first of these, the corpuscle is granular, and in the second, nucleated : when in the former phase, it is denominated "granule blood cell," and in the latter, "nucleated blood cell;" the first condition, or that of granule blood cell, is synonymous with the colourless corpuscle of the blood.

But each of these two phases presents likewise two stages in their growth or formation; thus the granule blodd cell may be either coarsely granular, or it may be finely granular ; and the nucleated blood cell may be either uncoloured or coloured. The first three stages are encountered, according to Mr. Jones, in the whole animal series, but not the fourth stage, the coloured condition of the nucleated blood cell, which is wanting in most of the Invertebrata, and in one of the series of Vertebrate animals, a fish, the Br ancliio stoma lubricum Costa; in all the other divisions of the animal kingdom it is present, as in the Oviparous Vertebrata and the Mammalia.

In the latter class, the Mammalia, a third phase is super-added to the other two, that of a "free cellceform nucleus;" this appellation expresses the usual condition in which the blood disc in the mammalia is encountered, and in which no nucleus can be discovered.


This third phase Mr. Jones considers to be derived from the nucleated blood cell in its second stage; the "free cellaeform nucleus" being the escaped nucleus of the nucleated blood cell.

The facts by which this view is supported are, first, a relation in size between the nucleus of the nucleated blood cell and the ordinary blood disc, or "free cellaeform nucleus," and second, the occurrence, which is, however, very rare, of nucleated cells from which the nuclei themselves have escaped.

The "nucleated blood cell" Mr. Jones found abundantly in the blood of an embryo ox, an inch and a quarter long ; very sparingly in that of the elephant and horse, and not at all in the blood of the human subject; he encountered them, however, freely in the chyle of man.

Such is a brief statement of the views of Mr. Jones in reference to the blood corpuscle, and of the chief facts by which those views are supported. Without taking upon myself to pronounce upon them decidedly, I yet must confess that they carry with them but little conviction to my mind, and that the facts adduced to sustain them are open to considerable discussion.

If the blood corpuscles of animals in general, and of the mammalia in particular, pass through the successive phases and stages described by Mr. Jones, how happens it, I would ask, that in the blood of mammalia, and especially in that of man, while we meet with so abundantly the first stage of the first phase, that of granule blood corpuscle, viz : the coarsely granular stage, and also the last phase indicated by Mr. Jones, that of free cellaeform nucleus, we do not frequently encounter the intermediate stages and phase, through which, according to Mr. Jones, the blood corpuscles pass? To this question I do not think it easy to give a satisfactory reply, consistent with the opinions of Mr. Jones. The explanation which I would give of the absence of these transition forms is, that they have no real existence.

According to Mr. Jones, the nucleated blood cells of the Oviparous Vertebrata are of a nature totally distinct from the ordinary blood cells of the Mammalia, which have no nuclei, but that the nuclei of the blood cells of the former are the analogues of the latter; this opinion is scarcely consistent with the difference of structure and chemical composition observed between the two. Opinions very analogous to those of Mr. Jones in reference to the nature of the blood corpuscles of the mammalia, viz : that they are escaped nuclei, appear to have been entertained by Mr. Gulliver from observations made on the horse; this gentleman supposing that the red corpuscle was the escaped nucleus of the white granular corpuscle, while Mr. Jones conceives that the red blood disc is the liberated nucleus of the same body, only in an advanced condition of its development, in the stage of coloured nucleated blood cell.

To the appellations by which Mr. Jones designates two of his phases of the development of the blood corpuscle, an exception may fairly be taken. The "granule blood cell" is frequently nucleated, even while it still retains its granular structure, and therefore the term selected by Mr. Jones to indicate a condition of the blood corpuscle distinct from its granular state, viz : that of nucleated blood cell, is inappropriate, and calculated to lead to the inference that the granule blood cell is not a nucleated body.

I reiterate then the opinion, that the white and red globules of the blood are wholly distinct from each other — distinct in origin, in structure, and in function.

The strongest fact with which I am acquainted (but it is one which is not employed by M. Donne) in favour of the transmutation of white globules into red, is this, viz : that the nucleus which exists in the blood discs of the frog, and reptiles in general, is of a granular structure, in all respects similar to that of a white globule, with the differences only of size and form, the nucleus being four or five times smaller than the true white globule, and of an oval instead of a circular outline. (See Plate II. fig. 5.) One of these differences, as already stated — viz : that of form — is effaced by water, which renders the nucleus circular (see Plate II. fig. 4), in which state the only distinction between it and a white corpuscle, which can be detected, is the single one of size. (See Plate II. fig. 1.) This difference, however, is so great, and coupled with the fact that no white globules have ever been detected in the frog, putting on the characters of a true red blood corpuscle, that the opinion that the white globules are transformed into red blood discs, must again be abandoned. The existence of a granular nucleus in the blood discs of reptiles, &c, revives again the old notion, that the white globules are the escaped nuclei ; that they are not so, is proved by the fact that no such nuclei exist in the true blood globules of man and the mammalia, in the blood of which white corpuscles abound.* The blood discs, it has been observed, first make their appearance in the chyle: any inquiries, therefore, instituted with the view of determining their origin and development in man, would be more likely to prove successful if directed to the rigorous examination of that fluid.*'


  • The following interesting remarks of Mr. Gulliver tend to confirm somewhat the

views of M. Donne; they are by no means conclusive, however: — "White globules, about the same size as those in the blood of man, and probably identical with the proper globules of chyle and lymph, are common in the blood of birds, and particularly abundant after a full meal in the vultures and other rapacious families.



In the last place, it remains to treat of the end or final destination of the red globules of the blood.

THE END OR FINAL CONDITION OF THE RED GLOBULES.

Every where throughout the solid constituents of the animal organization, cellular tissue abounds ; it forms the basis of every texture and organ of the body. It is, therefore, scarcely to be wondered at that the opinion should have been adopted, that the globules which exist in such vast numbers in the blood were to be regarded as the primary and even parent cells, out of which all the solid structures of our frame took their origin. f This theory, to the mind of the earlier micrographer, must have appeared very rational and seductive; and so great, indeed, is the plausibility with which, even in the present day, it is frequently invested, -that it is still able' to claim a few adherents.

Some of the red discs, too, instead of the oval form, are often nearly or quite circular in figure. Hence the blood of these birds would appear especially favourable to observe any changes in the white globules ; and it seemed highly probable that these might be transformed into the blood discs in the manner mentioned by Dr. Baly; but although I made many observations with the view of determining this question, nothing but negative results were obtained." — (Appendix to Gerber's General Anatomy, p. 24.) This observation is satisfactory in one respect, viz : that it shows clearly the connexion, which has already been dwelt upon, of the white corpuscles with nutrition.

  • For further observations on the development of the red blood disc, see the

remarks on the circulation in the embryo of the fowl.

f Among those who regard the blood corpuscles as cells, may be named Schwann, Valentin, Addison, Remak, and Barry. Schwann describes the blood globule as a "nucleated cell," while Valentin considers it to be a nucleus, and that which is usually held to be a nucleus he regards as a nucleolus. Remak states, that he has witnessed the development of the globules as parent cells, not within the blood, but within the cells which line the walls of the blood vessels and lymphatics. The views of Addison are confined chiefly to the white globules, which he conceives to be the fully-developed nuclei of the red blood corpuscles, and which he believes to be transformed into epithelial cells, &c, &c. Dr. Barry goes further than this; for he states that every structure which he has examined arises out of the blood corpuscle, "the crystalline lens itself, and even the spermatozoon and the ovum." The opinions entertained by Gerber seem to be of a nature somewhat similar to the foregoing. It is difficult to understand, however, what his exact sentiments are: they, at all events, go to the extent of supposing that all the solid structures of the body are derived from preexisting germs, contained in the chyle and blood.



If we regard with the utmost patience and attention the beautiful spectacle of the capillary circulation in any of the more transparent parts of animals, but especially in the tongue of the frog, we shall in vain look for the escape from their containing vessels of even a single red blood corpuscle, independent of a rupture of those vessels. In a normal state, therefore, the blood globules are never free, but are always enclosed in their own proper receptacles.

A communication, however, between the fluid contents of the blood vessels and the tissues lying external and adjacent to them, is doubtless established, through the operation of the principle of exosmosis, whereby a slow exudation of the fluid fibrin of the blood is perpetually going forward. Now, it is the opinion of most of the German physiologists, and it is the view best supported by facts, that this fluid fibrin is to be regarded as the true blastema, out of which all the different elementary tissues and structures of the body proceed, and this not by any power inherent in itself, it being, as respects the final form which it is made to assume, totally inert and indifferent, and which form is impressed upon it by a vis insita, or peculiar power and faculty belonging to each organ and structure of the animal fabric.

While the fibrin circulates in the blood it retains its fluid form ; soon after the cessation of the circulation, and whether within or without the system, it passes from the fluid state to the condition of a solid. Now, on the principle of endosmosis, which has to be so often referred to in the explanation of numerous phenomena, in the solidifying power of the fibrin, and in the vis insita of the different tissues, we recognise the chief and fundamental causes which regulate nutrition, growth, and secretion.

It would thus appear that the globules of the blood (the red globules are more particularly alluded to) are not to be regarded as either cytoblasts or primary cells, forming by direct apposition the solids of the body, and that therefore they do not express the last degree of elaboration of which the fibrin of the blood is susceptible.

Again, then, we have to ask ourselves the question, what is the end, or final condition, of the red blood globules? Direct observation is wanting to aid us in the solution of this difficult inquiry, which, however, admits of an indirect reply being given : we have seen that no means of egress from the blood vessels is, under ordinary circumstances, permitted to the red blood globules, and therefore we are driven to the conclusion that, having performed the important function to which we have already alluded, viz: that of carriers of oxygen from the lungs throughout the system, and of carbon from the latter back again to the lungs, they become dissolved, increasing by their dissolution the amount of fluid fibrin circulating in the blood, and which is deemed to be the true blastema.

MOLECULES OF THE BLOOD.

In addition to the red and the white globules, there exists, as already mentioned, in the blood a third description of solid constituent, the "molecules:" these are synonymous with the "basin-shaped" granules of Vogel, the "globulines" of Donne, and the "primary discs" of Martin Barry.

The term molecule, or granule, is well suited to designate these particles; for either appellation will serve to convey some idea of their exceeding minuteness, and which is computed rarely to exceed the 30^00 °f an inch. They occur in great quantities in the blood, either scattered singly throughout it or agglomerated into small and irregularly shaped masses. (See Plate I- fig- 6.) The molecules are usually regarded as the elements out of which the blood corpuscles are formed : on this point, however, direct observations are still wanting. It is more probable that the white globules are developed out of them than the red, and this simply by their union or aggregation.*

PECULIAR CONCENTRIC CORPUSCLES.

Besides the red and the white globules and the molecules, which we have described as present in the blood, a fourth species of solid corpuscle has been observed to occur in its fibrinous constituent. These corpuscles have been repeatedly encountered by Mr. Gulliverf in clots of fibrin in man and other mammalia, and are alike to be found in them, whether the clots are formed in the body after death, or in blood abstracted from the system during life.

  • Since the above few lines were written on the "molecules" of the blood, I have

repeatedly remarked that in blood, on its first abstraction from the system, but few molecules were present, while in that which has been withdrawn from the body for some time, they have always abounded. This observation has led me strongly to suspect that the molecules do not exist in the blood in a free state, but that wherever and whenever they are encountered, save only in the chyle, they are to be considered as derived from the rupture and destruction of the white corpuscles.

f See translation of Gerber, p. 31, and Appendix, p. 16.

These corpuscles, of a very peculiar structure, as will be seen hereafter, Mr. Gulliver has described and figured with extreme accuracy ; and he has styled them "organic germs," "primary or nucleated cells," and as capable of further development if placed in circumstances favourable to their growth. Mr. Gulliver, however, would appear to have been quite undecided as to their real nature, and whether they were not to be regarded as identical with the "fibrinous globules " of Mandl.

These peculiar bodies I have myself met with in fibrinous clots which were found in the heart after death ; and I have no hesitation in asserting that they differ, in every essential particular, from the fibrinous globules of Mandl, which are identical with the colourless corpuscles of the blood.

The size of these corpuscles is subject to the greatest possible variation; they are frequently smaller than the white globules of the blood, but very generally three or four times larger; their form is also irregular, but inclining, in those I have examined, to the spherical. They consist of two parts, of nuclei and envelopes : the nucleus is of an irregular outline, and not usually well defined without the aid of reagents; its bulk is about the one-fourth or one-fifth of that of the entire corpuscle; the envelope, in all the globules which have fallen under my observation, has been compound, that is, made up of several vesicles concentrically disposed, the one within the other. (See Plate IV. fig. 3.)

The appearance presented by these objects bears a close resemblance to the vesicles of certain species of Algae, of the genus Microcystis or Hcematococcus, these being likewise each composed of several concentrically arranged membranes or vesicles.

Now, what is the opinion which ought to be entertained in reference to the nature of these corpuscles? Do they really constitute an integral portion of our organization? and do they circulate in the living blood? or are they formed in it after death? The opinion of Mr. Gulliver that they are primary, or nucleated cells, has already been referred to : my own impression as to them is, that they do not constitute an integral portion of our frame; and that, whether they exist in the living blood, and circulate in it, or are formed in the clot subsequent to decease, they are to be regarded as extraneous formations, probably of an entozoal character.

It does not appear that the envelopes of all the corpuscles met with by Mr. Gulliver exhibited concentric striae, although he describes some of them as possessing this striated structure : Mr. Gulliver speaks also of cells three or four times larger than the corpuscles, and capable of containing the latter as nuclei. These I have not myself encountered.

The corpuscles are not usually scattered equally throughout the fibrinous clot, but frequently occur in groups, parts of each clot being altogether free from the corpuscles.

Acid reagents, especially the sulphurous acid, will be found useful

in their examination.*


BLOOD GLOBULES OF REPTILES, FISHES, AND BLRDS.

The red globules of the blood of the reptile, the fish, and the bird, have all certain characters in common with each other, which serve to distinguish them from those of man and the mammalia in general. The chief of these characteristics are their form, their size, the presence of a nucleus, and, lastly, their greater consistence. The compressed form belongs to the red blood globules of all animals ; in the three classes of reptiles, fishes, and birds, however, although the globules possess this flattened figure, instead of being circular, as in man and the mammalia, they are in outline elliptical ; and, in place of having a central depression, this part of each globule is slightly protuberant. This prominence is due to the presence of a nucleus, which in the mammalia we have seen to be absent.

The size of the red globules is as distinctive as their form, it usually exceeding, in reptiles, three or four times that of the majority of the blood corpuscles of mammalia. The blood disc of the frog equals in length the ttV j of an inch, while its traverse measurement is not less than the tgVj °f an inch; now the corpuscle of the elephant, the largest known among mammalia, reaches only the stV s °f an mcn m diameter, f

It has already been remarked that most of the animals of the order Camelidce are possessed of blood globules of an elliptical form, constituting in this respect an exception in the class to which they belong. These oval corpuscles are, however, so small, that they could not be readily confounded with the elliptical globules of the frog, &c. ; they therefore agree in size, as well as in the absence of a nucleus, with the blood corpuscles of other mammalia, although not in form. While every possible care has failed in satisfactorily demonstrating the presence of a nucleus in the blood of mammalia, not the slightest difficulty is experienced in detecting it in that of the frog and most of the animals belonging to the classes just mentioned, and therefore its presence is generally recognised ; although one excellent observer, M. Mandl, is of opinion that its formation takes place subsequently to the removal of the blood from the system : this idea is doubtless erroneous, as we have seen to be the case with respect to the white corpuscles of the blood, regarding which M. Mandl entertained a similar notion. In blood corpuscles immersed in their own serum, and examined immediately after their abstraction, the nucleus may be seen with a sufficient degree of clearness to enable the observer to pronounce with confidence upon its presence. After the lapse of a few minutes, it becomes much more apparent, so that its composition is easily to be discerned: this arises, most probably, from the discharge of a portion of the colouring matter of each globule. The form of the nucleus is seen to correspond with that of the blood corpuscle itself, and to be oval, presenting a granular structure precisely resembling that of the white globules of the blood, from one of which it is only to be distinguished by its much smaller size and oval form. (See Plate 11. fig. 2.)

  • Since writing the above description, I have met with these concentric corpuscles

in connexion with the thymus gland which had been allowed to remain in water for a few hours.

f The largest blood corpuscles hitherto discovered in the animal kingdom are those of the Siren and Proteus. In the Siren, according to Mr. Gulliver, the long diameter of the blood discs is the 435th, and the short the 800th part of an inch, while in the Proteus they are stated at about the 350th part of an inch in length.



Owing to the firmer texture and greater size of the blood globules of the frog, their structure can be well studied, and the effects of reagents more easily determined.

In water, the red corpuscles lose their colour, and become circular, and indeed globular, a change of form which the nucleus is likewise seen to undergo. (See Plate II. figs. 3 and 4.) These alterations ensue almost immediately on the application of the water; its continued action produces an effect still more remarkable; the nucleus, which at first occupied a central position in the globule, is soon seen to become eccentric, and finally, rupturing the pseudo-membrane of the corpuscle, escapes into the surrounding medium; the nucleus and the outer portion of each globule are then observed as two distinct structures, lying side by side (see Plate II. fig. 4) ; the latter is at length absorbed, and then nought remains but the nucleus, which is, as already remarked, under the influence of water rendered of a globular form, and which is in no way distinguishable from a white corpuscle of the blood, save in the single particular of size, the nucleus being several times smaller than the globule.

Acetic acid dissolves (if strong, almost immediately) the outer tunic, without occasioning the prior extrusion of the nucleus, the form of which is not materially affected, the contained granules merely becoming more clearly defined. (See Plate II. fig. 5.)

The white globules in the blood of the frog are very numerous; they bear no similitude of form or size to the elliptical red blood corpuscles, being usually perfectly spherical, and scarcely more than a third of the dimensions of the oval corpuscles. Thus, between the white globules in man and the mammalia and those of reptiles, an opposite relation of size in reference to the red blood discs exists; for while, in the former, the white corpuscles are larger than the red globules, in the latter they are generally much smaller. (See Plate I. fig. 1, Plate II. fig. 1.)

The plastic property possessed by the blood globules of all animals belongs especially to that of the frog. The globules, if trailed or drawn along the surface of a piece of glass, may be elongated to thrice their original length, and made to assume such forms as are altogether inconsistent with the existence of a thin and distinct investing membrane.* (See Plate II. fig. 6.)

CAPILLARY CIRCULATION.

We have now considered the blood, both physiologically and anatomically, out of the system, at rest and dead. We have, in the next place, to treat of it within the body, living and circulating.


  • The extraordinary elongation of which the blood globules of the frog are

susceptible, may be seen to very great advantage by adopting the following littleexpedient: — A drop of blood being placed upon the object-glass previous to its coagulation, and allowed to remain there for a few seconds, until symptoms of consolidation have manifested themselves, it is then to be extended gently with two pins in opposite directions; if now the microscope be brought to bear upon it, elongated corpuscles will be seen in it in vast quantities. In the production of this change, it is the fibrin which is mainly concerned; for it is through it that the extension is communicated to the corpuscles.

The beautiful phenomenon of the capillary circulation may be witnessed in the more transparent parts of several animals; as, for example, in the extremities of young spiders, fins of fishes, in the gills of the tadpole and the newt, in the tail of the water newt, in the web of the frog's foot, and in the mesentery of the smaller mammalia. But it is seen to the greatest possible advantage in the tongue of the frog; an organ peculiarly adapted for the representation of the circulation of the blood, from its extraordinary elasticity and transparence. For a knowledge of this fact, science is indebted to a neighbour and friend of mine, Dr. A. Waller, and by whom it was communicated some years ago to M. Donne. For the exhibition of the circulation in the tongue of the frog, in a satisfactory manner, it is necessary that the animal should be secured in the following way : — A bandage having been passed several times around the body of the frog, so as to secure effectually the anterior extremities, it is next to be fastened to a piece of cork by additional turns of the bandage; this piece of cork should be very thin, six or seven inches in length, by about ten in width, and perforated at one extremity by a square aperture, the diameter of which should not be less than two-thirds of an inch. To the margin of this aperture, the mouth of the frog, in binding it to the piece of cork, should be brought. The frog having been thus effectually secured, the soft and pulp-like tongue should be drawn out of the mouth by means of a pair of forceps, and being spread over the surface of the aperture, should he retained in position by from four to six pins, the elasticity of the tissue of the tongue allowing of its extension into a thin and transparent membrane with but little risk of a rupture of the organ; lastly, the piece of cork should be fastened to the stage of the microscope, in such a position that the tongue rests over the opening in the stage. These preliminary arrangements being effected, and a low power of the microscope being brought to bear upon it, a spectacle of the highest interest and beauty is revealed to the sight of the beholder. We have displayed before us, in action, almost every tissue of the animal organization, in its simplest and clearest form and disposition — arteries, with their accompanying veins and nerves; muscular tissue; the blood, with its red and white globules; epithelial cells; glands of the smallest possible complication of structure ; and these several parts are not merely visible, but their form, disposition, construction, and normal mode of action, are all distinctly apparent ; the blood ever flowing, the muscles contracting, and the glands secreting.

The circulation in the tongue of the frog is best seen, in the first instance, by means of low powers, a larger surface of the organ being thus brought under view, and a more exact idea obtained of .the relative size and disposition of its numerous constituents. The arteries may be distinguished from the veins by their fewer number, smaller calibre, and by the fact that, while the veins increase in diameter, in the direction of the course which the blood contained in them pursues, the arteries decrease in the course which the current follows in them. The arteries, from their origin, diminish in size and multiply in number, by the constant giving off of secondary branches ; the veins, on the contrary, become enlarged during their progress, and lessen in number, by the continual addition of subsidiary veins. These differences, as well as the circumstance that the velocity of the blood in the arteries is greater than in the veins, are abundantly sufficient to distinguish the two orders of vessels from each other. If, now, a somewhat higher power be applied to the objects, we shall be able to dive still further into the mysteries of organization ; we shall not merely perceive the general motion of the blood, but also that nearly the entire mass of that fluid consists of red globules. We shall be able to recognise clearly their form, and to see the different modifications of shape which they undergo in passing by each other, and in escaping any impediment which presents itself to impede their progress. We shall perceive, likewise, that, in the smaller capillaries, the globules circulate in single series, and mingled with them will be noticed occasionally a colourless globule, which, in the blood of the frog, is not more than half the size of the elliptical corpuscle. (See Plate V. fig. 2.) Furthermore, it will be remarked that the circulation does not flow on in an uninterrupted stream of equal velocity, but that certain arrests of its motion occur. These are but momentary, and after each the current again quickly flows on with the same speed as before ; with each action of the heart, also, a slight impulsion of the blood in the capillaries may be clearly seen.

This instructive sight of the capillary circulation may be viewed thus for hours, during the whole of which time the blood will be seen flowing on with undiminished force. In certain vessels, however, after a very long exposure of the tongue to the action of the air, w r hereby its moisture is continually abstracted, and which acts, doubtless, as a source of irritation, a number of the colourless globules will be seen to have collected in the capillaries; these adhere principally to the sides of the vessels and to each other, thus leaving the channel still free for the passage of the red globules, which in their course sometimes rush against the white globules with such violence as to detach one or more of them from time to time from its adhesion to the walls of the vessel, and which, rolling over once or twice, joins the general current of the vessel, and is quickly carried out of view. It would appear that any irritation affecting the capillary vessels, even when applied to them outwardly — as, for example, weak chemical solutions — gives rise to the phenomenon in question. It is to be observed, however, that at all times considerable numbers of white corpuscles circulate in the larger capillaries : these do not occur mixed up with the red blood corpuscles ; but, as already remarked, are situated externally between them and the inner wall of the capillaries. (See Plate ^.fig- 1.)

In the plastic power with which the red corpuscles are endowed, we recognise a beautiful and important organic adaptation of matter to the fulfilment of a special purpose. Were it not for this plastic property, and were the red corpuscles of the blood, on the contrary, of a solid and unyielding texture, it would follow, as an inevitable consequence of the solidity of the globules, combined with their vast number, that frequent interruption and stoppage of the circulation in the capillaries would ensue, and which would, of course, result in the complete derangement of the functions of the entire economy.

I come now to record an observation which, so far as I am informed, is without parallel. On one occasion, in examining the tongue of a frog, a portion of it broke away from the remainder; this I placed between two plates of glass, and submitted to examination, when, extraordinary to say, it was perceived that the circulation was still vigorously maintained in the majority of the vessels. Anxious to know how long this circulation would be continued, but fully expecting to see it cease every moment, myself and a friend, John Coppin, Esq., of Lincoln's Inn, watched it for upwards of an hour, at the end of which time the blood still flowed onwards in many of the vessels, with scarcely abated vigour, though in others, often the larger ones, the motion had altogether ceased. The mutilated portion of the tongue was then placed in water, in which it remained during the whole of the night; the next morning it was again examined, when it was found that a tolerably active circulation still existed in several of the smaller vessels. After this observation, the further examination of the fragment was abandoned. The almost immediate cessation of the circulation, which occurred in some of the larger vessels, admits of explanation in the following way: — In some vessels, the blood globules were seen escaping from their open extremities; this effusion of the globules frequently continued for two or three minutes, until the entire contents of such vessels became poured out, when of course the circulation within them ceased, the circulating fluid being expended ; in other capillaries, the current was seen to stop long before their contents had been exhausted, in which case it was usually to be remarked that some of the blood corpuscles contained in the vessels had collected around their orifices, thus producing an impediment to the further maintenance of the current.

The foregoing observation is one of much interest and importance; for it seems to prove that the capillary circulation is in a great measure independent of vital influences, and that its persistence is mainly due to physical agencies.

With a few observations on the mucous follicles situated on the upper surface of the tongue of the frog, we shall conclude our relation of the capillary circulation, as witnessed in that organ. These follicles are glands reduced to the simplest possible amount of organization: they are of a regularly spherical form, and transparent texture ; they are situated in the mucous membrane of the tongue, to the thickness of which they are entirely confined, as proved by the fact that, when that membrane is dissected off, by means of a needle the glands are raised along with it. Into each of these glands may be seen entering it on one side, and quitting it usually on the opposite, one of the smallest of the capillary vessels, in which the blood corpuscles pass usually in single series; this vessel in its passage through the gland describes usually a tortuous course ; and within it the blood corpuscles are seen to be in a state of increased and incessant activity, appearing to move, as it were, in a vortex, this appearance resulting from the curvatures described by the vessel. (See Plate VII. jigs. 1, 2.)

It might be expected that, in a gland of such simple constitution, the exact process of secretion would be rendered apparent ; in this expectation, however, we are doomed to disappointment, no action beyond that which we have already related being visible within it. An endosmotic action does doubtless take place between the contents of the gland and those of the vessel which permeates it, whereby a peculiar product is obtained from the blood, to be fashioned and assimilated by certain powers inherent in the gland itself, and the precise nature of which powers is unknown to us, and it is probable that it never will be revealed. Pass we now to the description of. the circulation in the embryo of the chick, which possesses points of interest distinct from those observed in the tongue of the frog.

CIRCULATION IN THE EMBRYO OF THE CHICK.

The process by which the circulation in the embryo of the chick is displayed is one which requires considerable delicacy of manipulation ; the care, however, which it is necessary to bestow upon it, for its successful exhibition, is amply repaid by the surpassing beauty of the spectacle which presents itself to the beholder. It is best seen in the third, fourth, and fifth days of the incubation of the egg.

For the purpose of showing it satisfactorily, the egg should be broken at the side, and a portion of the shell cautiously removed, without at the same time raising with it the subjacent membrane (membrana testae) ; this should next be peeled off with the same degree of caution as that with which the shell itself was previously raised.

Immediately beneath this membrane, the tyolk itself will be seen floating in the midst of the colourless albumen, and sustained in position by the beautifully spiral chalazce, which, proceeding from the yolk, are fastened into that portion of the membrana testes which corresponds with the poles of the egg-shell.

Imbedded in the surface of the yolk of an egg, on the third, fourth, and fifth days of its incubation, the embryo will be visible, and issuing from its umbilicus will be seen the vessels which ramify in such graceful order through the membrane of the allantois.

The embryo is almost invariably placed uppermost in the yolk, so that it most generally presents itself beneath, whatever part of the shell has been broken. This position results from the lighter specific gravity, and is, moreover, facilitated by the spiral formation of the chalazse.

The purposes fulfilled by this position of the embryo are obvious and striking, it being thus so placed as to receive directly the caloric which is continually emanating from the parent hen, and being also more immediately submitted to the influence of the oxygen of the air.

In an embryo then thus placed in situ, in the third, fourth, and fifth days of its development, and with the unaided sight, the rudiments of almost all the organs and members may be clearly recognised, the eye and the regular contractions of the heart, together with the vessels departing from it to ramify through the area vasculosa being particularly conspicuous. With a low power of the microscope, the course of the blood in the vessels, together with the form and size of the white and red corpuscles, may be clearly distinguished.

The ramifications of the vessels in the area vasculosa present an arborescent distribution ; their entire course may be traced from their commencement in the aorta to their termination on the border of the membrane of the area vasculosa.

Now, the great point of interest in the circulation of the chick is that the passage of the blood may be witnessed throughout. Thus, the blood expelled from the heart by the contraction of the ventricle into the aorta, may be traced through this vessel, and all its subsequent divisions and sub-divisions, until it reaches the ultimate arterial radicles, passes from these into the corresponding radicles of the veins, and from these again into the larger venous trunks, by which it is reconveyed to the heart, the circle of the circulation being thereby completed.

There are two ways in which the circulation in the embryo of the fowl may be viewed, either while it is still occupying its natural position on the surface of the yolk, (and this I think is by far the most preferable method,) or the embryo may be altogether detached from the yolk by means of an armed needle, and subsequently placed on a watch-glass filled with warm water at a temperature of 96°. During the operation of detaching the embryo, the egg itself should also be immersed in water at the temperature just mentioned. This latter process is one, however, of much nicety, and frequently fails in consequence of the rupture of some of the finer vessels, the blood becoming effused, the different parts of the embryo obscured, and a stoppage put to the circulation.

But it is not alone the contemplation of the circulation in the embryo of the chick which is so interesting and instructive; the study of the entire development of the ovum, from its commencement to its termination, reveals facts of the highest importance, and full of wonder.

The examination of the blood of the embryo fowl is especially instructive, the mode of formation of the red corpuscles admitting of determination in a manner the most satisfactory.

In the red corpuscles contained in the blood of the embryo in the first days of its development, a remarkable variation of size will be detected, some of them being three or four times larger than others, and the smallest consisting almost entirely of a nucleus surrounded by a faint and delicate envelope. Between the two extremes of size, every possible gradation is presented. (See Plate IX. fig. 1.)

This variation in the dimensions of the corpuscles becomes scarcely less apparent if they be immersed in water, in which they become perfectly spherical. (See Plate IX. fig. 2.)

A diversity of size, almost as remarkable as that which exists between the red blood corpuscles of the embryo fowl, will be observed also in those of the young frog which has but just emerged from its tadpole state. If a drop of the blood of this young frog be compared with that of a full-grown frog, the corpuscles in the former will be remarked to vary greatly in dimensions, while in the latter they will be seen to present a much greater uniformity of size. (See Plate IX. figs. 4, 5.)

Now, the inferences to be deduced from this great diversity of size are palpable, and are, first, that the red blood corpuscle is at its origin small, and only attains its full dimensions after a given period ; and, second, that the nucleus is the part of the corpuscle which is first formed, the coloured investing and perfectly smooth portion of it being gradually developed around this subsequently. This view is inconsistent with the notion entertained by many, that the red blood corpuscles result from the gradual assumption by the white globules of the characteristic distinctions of the red blood discs ; for were this really the case, we should be at a complete loss to account for the remarkable differences of size to which we have adverted.

A similar mode of development to that which has been described as belonging to the red blood corpuscles of the embryo fowl, appertains also, I believe, to that of all the Oviparous Vertebrata.

The development of the coloured blood corpuscle of the Mammalia, I conceive to agree also with that of the other Vertebrata in the fact of its being small at first, and subsequently and gradually attaining its normal proportions, but to differ from that of the Oviparous Vertebrata in not being developed around a central nucleus.

DISSOLUTION OF BLOOD CORPUSCLES.

But if the blood of the embryo fowl is well adapted for the study of the origin and development of red blood corpuscles, that of the adult fowl is no less fitted for ascertaining their end and final destination.

Some observers have entertained the idea, already expressed in this work, that the older blood discs become melted down in the liquor sanguinis, and thus, by their dissolution, increasing the amount of fibrin held dissolved in that liquid. To the adoption of this notion they were driven, because they were unable to dispose of the red blood disc in any other way, and which other facts had made apparent to them could not be regarded as persistent structures.

In proof of the accuracy of this statement respecting the melting down of the corpuscles, they had not, however, a particle of direct evidence to adduce. I will now proceed to show that the view referred to may be substantiated by positive observation.

In almost every drop of the blood of an adult fowl, a number of certain pale and usually colourless corpuscles will be seen, having a nucleus of the same size and structure as that of the ordinary red blood disc distinctly visible in the midst, the investing portion of each corpuscle at the same time being invariably smooth and destitute of granules.

These corpuscles vary in size, in form, and in colour; the larger ones, which are equal in dimensions to the fully-developed blood discs, usually retain a faint colouration, and are invariably of an oval form ; while the smaller ones, many of which consist of merely a nucleus and a closely-fitting envelope, are perfectly colourless, and for the most part, although not always, spherical. (See Plate lH-fig. 3.)

Now, there is no difficulty whatever in detecting these pale and mostly spherical corpuscles with a good instrument, nor is there the slightest danger of confounding them with the white corpuscles, which are also to be seen retaining their uniformly molecular aspect.

The corpuscles just described exist not merely in the blood of the adult fowl, but they may be detected, with similar facility, in every Oviparous Vertebrate animal the blood of which I have examined; and they abound in the blood of tritons and frogs. (Plate IX. j6g\ 5.)

But further, there may be detected in the blood of adult Oviparous Vertebrata, not merely the delicate and pale corpuscles referred to, but also numbers of naked nuclei — that is, of nuclei deprived of all trace of investing membrane. (See Plate IX. figs. 3 and 5.)

These nuclei should, however, be examined with care, and a nice adjustment of the object-glass ; for it will be found, on close examination, that many of them, though appearing at first sight to be naked, are not really so, but are invested by a scarcely-perceptible envelope.

Now, these large and slightly-coloured oval corpuscles, the smaller perfectly colourless and mostly spherical ones, and the naked nuclei, represent progressive states of the dissolution of the red blood disc.

When first I noticed these pale corpuscles and nuclei, I was disposed to think that they represented stages in the upward development of the red blood disc : this opinion was, however, dispelled, by observing that the pale and colourless corpuscles often exceeded greatly in size the smaller true and coloured blood corpuscles.

There is one circumstance connected with these pale corpuscles which does not appear to admit of any very satisfactory explanation, viz : their occurrence on the field of the microscope in groups.

A word or two as to the seat or locality in which the w T ork of development of blood corpuscles, and subsequent dissolution of them, is conducted. Physiologists appear always to have been on the look out for some organ of the body, the especial purpose of which in the animal economy they conceived should be the elaboration of the blood corpuscles; and some of them, as Hevvson and Donne, not knowing well what office ought to be assigned to that much-discussed organ, the spleen, have on various grounds considered it to be the laboratory in which the work of development is carried on. Of the dissolution of the red blood discs, no definite or decided observations hitherto appear to have been made by any observer.

Observation has convinced me that the development of blood corpuscles is not assigned to any particular organ of the body, but that it occurs within the blood-vessels during the whole course of the circulation and of life. During the first formation of the blood in early embryonic life, the corpuscles are said to be formed in the cells, which by their union with each other give origin to the capillary vessels.

Further, it is probable that, while it is in arterial blood that the work of development of blood corpuscles is most active, it is in the venous fluid that the converse work of dissolution is mainly effected.

The development of blood corpuscles is also most active in very early life, when growth is rapid ; and it is likewise more active than ordinary in adult existence, after haemorrhages, and in persons of the plethoric diathesis. In like manner it may be presumed that the dissolution of red blood corpuscles proceeds more quickly in anaemic conditions of the system, and in old age, while at the same time, at the latter period, development of new corpuscles is more tardy.

It is now hoped that a more satisfactory explanation of the origin and end of the red blood disc has been given than it was feared, when the writer first approached the consideration of these difficult, though most important, questions, it would have been in his power to have afforded.

VENOUS AND ARTERIAL BLOOD.

Venous and arterial blood differ in certain important respects from each other; arterial blood is of a brighter colour, and coagulates more firmly than that which is venous. The difference in colour is due to the presence in the former of oxygen, and in the latter of carbon in a state of combination not yet well determined. Venous blood, when exposed to the action of oxygen, soon acquires the vivid red colour of arterial blood, and this, when submitted to the influence of carbonic acid, as speedily assumes the dark hue of venous blood.

The greater or less firmness in the clot formed is owing to the different amount of fibrin contained in the two fluids, and which is greatest in that which is arterial ; the coagulum of which, therefore, possesses the greatest density. The differences detected by the microscope in the blood corpuscles of arterial and venous blood are scarcely appreciable. Gerber states that the "tint of colour exhibited is various ; bright in the globule of arterial blood, dark red and somewhat streaky in that of venous blood :•" this difference of colour, which doubtless exists, it is easier to infer than positively to demonstrate by means of the microscope. While arterial blood is richer in salts, venous blood contains a greater proportion of fatty matter.

There are several substances which effect a change in the colour of the blood : thus, oxygen, the concentrated solutions of salts with an alkaline base, and sugar, turn dark venous of a bright florid or arterial red ; this reddening being accomplished by the salts and sugar, even when the blood is placed in a vacuum, or an atmosphere of hydrogen, nitrogen, or carbonic acid gasses.

Newbigging* hath also remarked that venous blood takes the tint of vermilion in a cup, at those situations at which it is painted with the green oxide of chrome ; and Taylorf has confirmed the observation that the colours which contain the oxide of chrome brighten the tint of blood.

On the other hand, bright or arterial blood is darkened, or even blackened, by contact with carbonic and oxalic acids, and by its admixture, according to Henle, with distilled water.

Sulphuric acid, and other acids which are agitated with the blood, change its colour from red to blackish brown.

The nitrous and nitric oxides cause vermilion blood to take a deep purple tint. J

The power possessed by those substances which brighten the colour of dark venous blood, is supposed to be derived from the oxygen which they contain, and by means of which a chemical transformation in the condition of the red element of the blood, the hematine, is effected, a portion of oxygen being absorbed during the change of colour. Those substances, however, which cause arterial blood to assume the tint of venous blood, are presumed to exert their influence by means of the carbon of which they are compounded, and a portion of which becomes imbibed during the work of transmutation.

  • Edinburgh New Philosophical Journal, October, 1839.

f Lancet, February, 1840.

| Henle, Anatomie Generale, tome premier, page 471.


Henle, nevertheless, considers that these several alterations of colour arise rather from mechanical than chemical causes, and that they depend upon the state of aggregation of the particles of the colouring matter, these being differently disposed according to the nature of the reagent employed.

Thus, Henle remarks*, " It is evident that the colour of the blood is brightened under the influence of substances which oppose the dissolution of the hematine in the serum, and maintain or reestablish the flat form of the corpuscles, as the concentrated solutions of salts and of sugar ; while pure water, which dissolves the colouring matter, and causes the corpuscles to swell, deepens the colour of the blood."

Hamburgerf , according to Henle, has even observed that weak solutions of the chlorides render the colour of the blood deeper, while their concentrated solutions make it pass to vermilion.

Again, according to the observations of Schultz, it would appear that the red blood corpuscles are flattened by the action of oxygen, while the effect of the application of carbonic acid is to cause them to swell up, and assume a more or less globular figure.

On this fact, Henle reasons thus : Accompanying these changes of form there are alterations in the state of aggregation of the colouring matter of the corpuscles; thus, in oxygen, or in any saline solutions, the plasma remains clear and colourless, the blood discs being flattened, and the colouring matter contained within them condensed; while in carbonic acid or water the plasma becomes coloured, by the escape of a portion of the hematine from the corpuscles, which swell up, and assume a form approaching more or less the globular.

Now, the difference in colour between venous and arterial blood Henle maintains may be accounted for by reference to the form of the corpuscles, and the consequent condition of the particles of the colouring matter.

And it is also by reference to the state of the colouring matter that Henle accounts for the fact that blood which has once acquired a very dark colour is thereby rendered incapable of reassuming the bright hue of arterial blood on the application of oxygen or saline solutions, because, he says, that the pigment which had escaped into the plasma, under the influence of the carbonic acid, cannot be made to enter into the corpuscles again, when by means of oxygen they are again flattened.

  • Loc. cit. page 471.

f Hamburger, Exp. circa Sanguinis Coagulationem, pp. 32. 42.


The colour of the blood, then, according to Henle, depends upon the single fact of the form of the corpuscle, and that this colour is so much the more bright as these are flat.

Finally, in support of his theory, Henle refers to changes of colour presented by certain inorganic substances from an alteration in the state of aggregation of its constituent particles: thus, it is well known that the ioduret of mercury recently sublimed is yellow; in cooling, its colour passes to scarlet, and pressure determines this change in an instantaneous manner.

Such is Henle's mechanical theory of the changes of colour experienced by the blood on the addition of reagents ; a theory which, however ingenious it may be, I deem to be insufficient to account for the very remarkable alterations of colour to which the vital fluid is subject.

The changes of colour of dark blood to a vermilion hue, and of this again to the deep tint of venous blood, admit of a chemical explanation being given, the essential element of the former change being oxygen gas, and of the latter carbonic acid gas. Thus, even the remarkable effect of the application of the chlorides may be accounted for by reference to the well-known operation of chlorine as a bleaching agent, viz : through the power which it possesses of depriving water of its hydrogen, and altering the state of combination of the oxygen.

With respect to the observations of Schultz on the effect of carbonic acid and of oxygen in altering the form of the red blood corpuscles, and on which fact the entire of Henle's theory rests, I would observe that, in conjunction with Mr. Miller, the gentleman who manifests so much of patience, skill, and intelligence in the execution of the drawings of this work, and who is moreover an excellent chemist, I have made many experiments, with the view of ascertaining the power possessed by the former reagent in modifying the form of the elliptical corpuscles of the blood of the frog, the blood being in some cases submitted to the direct action of the gas, and in others the animal itself being subjected to its influence.

The result of these experiments, on my mind, is the conviction that the effect of this gas on the figure of the corpuscle is not appreciable. I am, therefore, disposed to allow but little weight to the mechanical theory of the changes of colour experienced by the blood.

Venous blood does not present precisely the same tint of colour, or the same characters in all parts of the system : thus, the blood found in the vena portse is deeper in colour than any other venous blood, and, according to Schultz, it does not redden either on the application of ox) T gen gas or of salts, and does not coagulate, or gives but a divided clot; it is richer in water, in cruor, and in fat, and poorer in albumen, than ordinary venous blood.

It would be a point of much interest to determine whether arterial or venous blood contains the greatest number of blood corpuscles. The experiments which have hitherto been made, with the view of determining this question, are most unsatisfactory, and contradict each other.

MODIFICATION'S OF THE BLOOD CORPUSCLES THE RESULTS OF DIFFERENT EXTERNAL AGENCIES.

Peculiar Modification of the Effect of commencing Desiccation.

If the red corpuscles be examined a few minutes after their abstraction from the system, in a drop of blood which has been spread out between two plates of thin glass, it will be seen that many of them, and especially those which are situated near the margin of the drop, present an appearance very different from that which belongs to them in their ordinary and natural condition. They now no longer exhibit the flattened form with the central depression, but have become converted into little spheres, the surface of which, instead of being smooth, is now rough and tuberculated. (See Plate I. fig. 5.) Blood corpuscles thus changed have been compared to mulberries in appearance. This alteration is supposed by Donne to depend upon commencing desiccation, and to arise from deficiency of serum, the mulberry-like globules being but imperfectly bathed in that liquid. No very satisfactory explanation of the exact nature of the change has as yet been given. MjM. Andral and Gavarret* suppose that the mammillated appearance of the corpuscles arises from the adherence, to the surface of the globules, of a number of the exceedingly minute molecules of the fibrin ; this explanation is probably more ingenious than correct. If a number of the altered globules be carefully and closely examined, it will be remarked that they do not all exhibit precisely similar appearances ; that in some globules, for instance, it will be observed that the contour is but slightly broken or indented ; that in others the indentations of the surface are more considerable, and the small spaces between them consequently more prominent; and again, in other globules, and which are indeed by far the most numerous, it will be obvious that the whole surface has become distinctly tuberculated, each tubercle, of which there are several to each globule, appearing to be of a spherical form, and resembling a minute bubble of some gas, probably of oxygen, or carbon, according as the blood is arterial or venous. That they are really of a gaseous nature is proved, I think, by the fact of their gradual formation as well as dissipation. M. Andral states, that in blood which has been deprived of its fibrin, the corpuscles never exhibit the peculiar granulated or tuberculated aspect which we have described ; and this fact he adduces in support of the opinion entertained by him, that this peculiar condition of the globules is due to the accumulation on their surface of the molecules derived from the fibrin.

  • Essai d'Hemalogie Pathologique, par G. Andral, page 23.


Mr. John Quekett is also of the opinion that this peculiar condition of the blood globules of which we have been speaking, is occasioned by the adherence to their edges of granules which he considers to be derived from the interior of the corpuscles themselves. See "Observations on the Blood Discs and their Contents," Microscopic Journal, vol. i. p. 65. For further observations on this granulated appearance of the corpuscles, see Part I. p. 31.

MODIFICATIONS THE RESULTS OF DECOMPOSITION OCCURRING IN BLOOD ABANDONED TO ITSELF WITHOUT THE BODY.

In blood abandoned to itself, and exposed to atmospheric influences, changes of form and appearance speedily begin to manifest themselves in the red corpuscles. These changes occur in regular order; they first become wrinkled, deformed, and tuberculated; they next lose their flattened and disc-like shape, becoming globular and smooth; their colouring matter escapes from them, and they present a livid hue. In this condition they are with difficulty discoverable in the blood ; finally, they dissolve, and all traces of them disappear. These successive changes are all produced in the course of a very few hours : the exact period, however, varies with the temperature of the atmosphere and actual condition of the blood when extracted from the system.

MODIFICATIONS THE RESULTS OF DECOMPOSITION OCCURRING IN BLOOD WITHIN THE BODY AFTER DEATH

The changes which we have described as occurring in blood abandoned to itself without the system, take place likewise in the red corpuscle of that which is contained within the body after death, and this even with a greater degree of quickness than in the former case ; the time, however, bears a relation to atmospheric conditions, to temperature, as well as, especially, to the nature of the malady to which the patient has succumbed. If the affection which has occasioned death be of a nature to exhaust profoundly the vital powers — if it be a chronic disease of long duration, as a typhoid fever — the period requisite for the production of these changes will be very short; so brief, indeed, that the alterations may be detected in the corpuscles almost immediately after the extinction of life. It is of much importance that the changes resulting from decomposition, and which occur in the dead body, should not be confounded with real and pathological alterations of the red corpuscles.

CAUSES OF INFLAMMATION.

Exciting Cause.

The fact which has been alluded to in the preceding pages, of the accumulation of the white and red corpuscles in the tongue and web of the frog, as a consequence of the application of irritation, bears a close relation to the phenomena of inflammation, and shows that the exciting cause of inflammation, whatever it may be — such as a blow, exposure to cold, burns, scalds, or the application of irritating substances — acts usually through the medium of the nervous system, the impression produced on it impinging upon the structures to which the ultimate nervous nbrillee are distributed, viz: the vessels in the which a series of results ensue which together constitute the condition of inflammation.

Proximate Cause.

When the white and the red corpuscles of the blood accumulate in the capillaries of a part in normal quantity, those vessels may be considered to be in a state of "vital turgescence ;" when, however, they are present in those vessels in abnormal proportion, then the capillaries may be said to be in a state of "inflammatory turgescence."

Now, the term "congestion" indicates a condition of the vessels intermediate between vital and inflammatory turgescence, and which may be denominated " congestive turgescence."

In vital turgescence, a phrase which indicates the condition of the vessels in a state of normal nutrition, the capillaries are slightly increased in calibre, and are pervaded by an unusual, though perfectly normal number of corpuscles, both red and white, but especially of the latter, some of which adhere to the walls of the vessels.


In congestive turgescence, or in congestion, the calibre of the capillaries is more considerably increased in size, and a greater and abnormal number of white and red corpuscles, especially the former, are collected in the vessels. These corpuscles, if the turgescence terminates in resolution without advancing to the condition of inflammation, do not undergo any structural changes, but enter again into the circulation, their removal being determined by the discontinuance of the exciting cause, and by the vis a tergo of the circulation, which drives the corpuscles onward.

Lastly, in inflammatory turgescence, the diameter is very considerably enlarged, and their interior is filled with a very greatly increased and abnormal quantity of white and red corpuscles, these accumulating to such an extent as either to seriously obstruct, or altogether destroy, the circulation in those vessels. This condition of the vessels is always accompanied by certain structural alterations, which effect not merely the corpuscles themselves, but also the vessels and parts adjacent to them ; these alterations being merely attributable to the impediment presented to the onward progress of the blood in the capillaries by the accumulation in them of the blood corpuscles.

We now know that the proximate cause of inflammation consists in an abnormal accumulation of the corpuscles of the blood in the minute capillary vessels, and which accumulation we perceive must inevitably impede the function of the part in which the vessels are thus surcharged, alter its structure, and finally tend to a sympathetic disturbance of the entire economy. For this discovery we are indebted to the microscope. It will thus be seen that some of the ancient hypotheses in reference to the proximate cause of inflammation were not so very far wrong, and that most of them recognise the fact, that it is the capillary vessels and blood corpuscles which are mainly concerned in the production of the phenomena of inflammation.

Finally, inflammation may, like congestion, terminate in resolution; but, unlike congestion, it always leaves permanent traces of its visitation, the resolution being but incomplete. It may terminate, also, in "hepatization," or in "purulent infiltration." The fibrin of the blood is the chief agent in producing the consolidation of the structure known by the term hepatization, while it is the white corpuscles analogous to those of the blood, as will be seen hereafter, that give rise to the purulent formation.


PATHOLOGY OF THE BLOOD.

We now come to the consideration of the most important division of our Chapter upon the Blood, viz: that which treats of the pathological changes which that fluid undergoes, and a full and clear understanding of which is so necessary to the safe and successful treatment of disease.

These pathological alterations are numerous, and engage not merely the solid constituents of the blood, the white and red corpuscles, but also its fluid elements, the fibrin and the albumen; the abnormal conditions of each of which principles of the blood we shall find to be accompanied by a distinct train of morbid phenomena. It may be- said that the fibrin and the albumen being entirely of a fluid nature, and not holding solid particles of any magnitude in suspension, they ought not to be considered in a work devoted to microscopic anatomy. We shall find, however, that these several constituents of the blood are so intimately associated, that, in order to understand any one of them fully, it is necessary that we should possess a knowledge of the others also, and therefore I consider that their discussion comes within the legitimate scope of this work.

For much of our knowledge of the pathology of the blood we are indebted to the united researches of MM. Andral and Gavarret, to whose valuable essay we shall have occasion hereinafter to make frequent reference.

Pathology of the Red Corpuscles of the Blood.

The scale of the red corpuscles of the blood, relative to that of the other elements, varies considerably, even in states of health. The mean proportion of red corpuscles is estimated by MM. Andral and Gavarret at 127 in every thousand parts of the vital fluid. This scale may, however, be elevated to 140, or depressed to 110; the variations in the quantity of the red globules within these limits being compatible, however, with a physiological or healthy condition of the blood, although the higher scale, 140, is allied to a state of plethora, while the lower, 110, borders upon the opposite state, of anaemia, and both of which may be regarded, if not as diseases in themselves, at least as powerful, auxiliary, and predisposing causes of many morbid conditions of the system.

Increase in the Number of the Red Corpuscles. — Plethora.

An increase in the number of the red corpuscles of the blood exists in that condition of the system which has been denominated the plethoric, and which increase constitutes its chief element. The authors already cited found the mean proportion of the red globules in the thirty-one cases in which the blood was submitted to examination, to be in every thousand parts 141 ; the minimum 131, and the maximum 154. With this increase in the number of the red corpuscles, it was not found that any other element of the blood had become either augmented or diminished.

The symptoms which indicate the existence of plethora, whether they be organic, or functional and mental, all admit of a ready and satisfactory explanation by a reference to the increased quantity of the red corpuscles.

The existence of a state of plethora implies high vital powers ; there seems to be in the plethoric, as it were a super-abundance of life, and which is imparted to all the parts and organs of the system alike. The plethoric diathesis would appear to be more frequently hereditary than acquired, and no degree of high and nutritious feeding will induce it in the system of some persons, although an opposite or anaemic state may be produced in all by the abstraction of a proper quantity of suitable nourishment.

The general symptoms which characterize the plethoric diathesis, are a well-developed muscular system, voluminous thorax, a deepcoloured skin, and a ruddy complexion; coinciding with these physical and outward appearances, we find much functional activity to exist, the respiration is free and unembarrassed, the digestion quick and active, the pulse is full and strong, and the motions of the body are performed with celerity and power. This functional activity appertains also to the operations and emotions of the mind; the plethoric is quick in thought, hasty and violent in temper.

The injected skin, the brilliant complexion, are to be explained by reference to the increased quantity of the red corpuscles which circulate in the blood, and which alone are the seat of colour, while the great organic development and the functional and mental activity depend partially upon the greater amount of oxygen of which the blood corpuscles are the carriers to all parts of the system, and which is so essential to the vigorous performance of the vital processes and manifestations.


The characters exhibited by blood which has been withdrawn from the system are likewise consistently explained by reference to the augmented quantity of the red blood corpuscles ; thus the blood in plethora, immediately on its abstraction, is observed to be of a deeper colour, and the clot formed subsequently by its coagulation of a larger size ; this, although voluminous, is of mean density, and never exhibits the buffy coat, which circumstances are accounted for by the fact that, as already remarked, in the blood of plethoric persons there exists necessarily no excess of fibrin.

Accompanying the plethoric condition, and dependent upon it, we have frequently a number of grave pathological manifestations, apoplexies, haemorrhages, congestions, vertigos, noises in the ears, and flashes of light before the eyes; all of which are most generally greatly relieved by venesection, which withdraws from the system a portion of the super-abundant red blood corpuscles.

Decrease in the Number of the Red Corpuscles. — Ancemia.

The term anaemia indicates a state of the system the very reverse of that which obtains in plethora: in it the red blood corpuscles, instead of being in excess, are greatly below the physiological standard. The authors quoted found, in sixteen cases of commencing anaemia, the mean of the red globular element of the blood to be 109; and in twenty-four examples of confirmed anaemia, 65; that is, almost one-half less than the standard which belongs to health. In one case of anaemia in the human subject, M. Andral found the scale to descend so low as 28 ; a depression which one would scarcely suppose to be compatible with life.

In spontaneous anaemia it is stated, that it is the globules alone which are affected, and that in it, as in plethora, the other elements of the blood undergo neither augmentation nor diminution ; in accidental anaemia, however, resulting from direct losses of the vital fluid, the normal standard is of course disturbed; for in haemorrhages, and especially in first bleedings, it is chiefly the globules which escape, and this would lead to the relatively higher scale for the fibrin.

As anaemia depends upon a condition of the blood the very opposite of that which exists in plethora, the symptoms also in these two constitutional conditions are the reverse of each other; instead of the vascular and injected skin, we find it to be livid and exsanguine, these appearances extending also to the mucous membranes; in place of the accelerated functions, we notice that the vital actions are sluggishly performed, and that the mental powers are feeble.

The blood abstracted from the system exhibits a paler tint than is usual, and the clot is small, and floats in the midst of the serum, which is very abundant; small, however, as the crassamentum is, it is yet of considerable density, as might be expected from the remark which has already been made, viz: that the fibrin exists in its normal proportion, and therefore is in excess over the globular element of the blood which is deficient; it is for the same reason also that we frequently notice upon the surface of the clot the buffy coat ; the density of the clot, and of the crust which covers it, are so much the more marked as the anaemia is considerable.

The existence of the miscalled inflammatory crust in anaemic states has long been known, although not satisfactorily accounted for.

The pathological disorders to which anaemia gives origin are numerous : the general debility, the disordered digestion, the difficult respiration, the palpitations of the heart, the faintings, are well remembered.

There is a state of the system, well described by Andral, which stimulates plethora, but which is really allied to anaemia, and to which the term false plethora might be given; in this we have the injected skin and many other indications of plethora; it is to be diagonosed, however, by means of the constitutional disturbances which coincide with those of ordinary anaemia.

It is in anaemic conditions of the system that we detect the remarkable bruit de soufflet, in reference to which Andral in his essay on the blood has instituted some useful researches, the chief result of which is the establishment of the fact, that the intensity and persistence of the bruit is in exact proportion to the severity of the anaemia.

In pregnancy we have a slight example of an anaemic condition of the blood, and in chlorosis we see anaemia to prevail with various degrees of severity. In phthisis the scale of the red corpuscles is likewise much reduced, but not to the extent to which its reduction is witnessed in chlorosis ; and this is the more remarkable from the circumstance that in the former disease it is those organs which are affected, between which and the red corpuscles a close connexion exists. In cancer also the number of the blood corpuscles is reduced: in phthisis the diminution precedes and accompanies the whole course of the affection, while in cancer it occurs only at an advanced period of the disease, and arises principally from the continual losses of blood to which cancerous patients are so subject. In disordered states of the system, purely nervous, we find also the red element of the blood to be deficient. The scale of the red globules in a number of cases in which the blood of phthisical patients was submitted to examination oscillated between 80 and 100.

Increase in the Number of the Red Corpuscles under the Influence of Recovery and of certain Medicinal Agents.

Under the influence of recovery the red blood corpuscles increase in number, and have a tendency to attain to their physiological standard, which, when reached, they may even exceed, until at length they mount up to the scale which denotes the existence of the plethoric condition.

Certain medicinal substances exhibit likewise much influence in increasing the number of the red corpuscles; of these the most remarkable is iron, under the effect of which remedy the pale complexion of the chlorotic will be seen gradually to acquire the tone and colour indicative of health and strength.

Effect of Disease upon the White Corpuscles.

The white corpuscles of the blood have not hitherto received that amount of attention which has been bestowed by so many observers upon their associates the red corpuscles ; indeed, it is only in these latter times that their investigation has been pursued with that degree of care which, from their importance, they so well merit, and observations are still wanting upon their condition in states of disease. It has already been remarked that an increase in their number has been frequently observed to occur in various diseases, and especially in such as are accompanied by suppuration and great exhaustion of the vital powers. Of the precise cause of this increase, no very satisfactory explanation has been offered, and the following attempt at an explanation is presented to the consideration of the reader with much hesitation. In most serious disorders, the function of nutrition and assimilation is more or less impeded. Now, supposing that these white corpuscles are essentially connected with nutrition, and that while the cause which determines their formation still continues in operation, that which regulates their assimilation is suspended, there would result, as an inevitable consequence, an accumulation of the white corpuscles in the blood.

Deficiency of Fibrin in Fevers, as in Typhus, Small-pox, Scarlatina,

Measles.

The important researches of MM. Andral and Gavarret establish the fact, that, in that much-debated class of maladies, fevers, there is a deficiency in the blood of its spontaneously coagulable element, the fibrin. In the Essai d 'Hematologic no scale of the diminution in the amount of fibrin is given; it is shown, however, that in some fevers, and especially in the commencement, the deficiency of fibrin may be but small; and that in others, particularly when symptoms of putridity have manifested themselves, and which may ultimately complicate all fevers, the loss of fibrin is considerable, and further that the intensity of symptoms is in direct relation to this loss, being great when the diminution of fibrin is also great.

It is not to be understood, however, that the deficiency of fibrin constitutes the essence or real and specific cause of fever; for this we must look to some other agent or fact, probably to the contamination of the general mass of the blood by the imbibition of some deleterious and subtle miasma. That the deficiency in the amount of fibrin is not the cause of fevers, we find to be proved by the facts that this class of maladies attacks persons of every possible variety of habit and constitution, and in many of whom, at the onset of the disorder, no deficiency of fibrin can be detected; and the same view is likewise confirmed by the circumstance which must have attracted the attention of every physician, viz : that the primary condition and inherent powers of the system determine and control but to a comparatively slight extent the course which the malady may take, and which course seems to be dependent upon the nature and quality of the infecting agent itself. The inference, then, which may be derived from the fact that a deficiency of fibrin exists in the blood of persons afflicted with fever, is, that the tendency of the cause of fever, a miasma, or whatever else it may be, is to occasion a depreciation of the physiological standard of the fibrin in the blood, and not that the deficiency is in itself the exciting cause of fever.

Between this diminution in the normal proportion of the fibrin and the various hemorrhages, which are so often observed to complicate fevers of all kinds, a corelation doubtless exists, although the precise manner in which this deficiency leads to such a frequent recurrence of hemorrhage is not clearly understood, and the only way in which this can be explained is by the supposition that in fevers from the cause assigned, viz : the small quantity of fibrin, the solids generally, and the blood-vessels in particular, lose a portion of their solidity, and readily give way to the force of the fluid contained within them.

The hemorrhages referred to are frequently observed in small-pox, in which the blood is effused into the pustules; in scarlatina, in which fluxes take place from various parts of the body; and in typhus, in which we- have frequent buccal hemorrhages, and the formation of petechiae.

Cotemporaneous with this diminution in the amount of fibrin, we do not find that any other element of the blood is constantly affected, although it occasionally happens that the red globules are in excess.

The clot in typhus, in which, of course, the deficiency of fibrin is considerable, is large, filling almost the entire of the vessel which contains it; is soft, being readily broken up on the slightest touch; it is flat, and ill-defined, and the serum in which it floats is of a reddish colour.

The flat form and softness of the clot is to be explained by reference to the diminished amount of fibrin, while its great size is accounted for by the imperfect expression of the serum from the crassamentum, as well by the fact that the red corpuscular element of the blood exists usually in its normal proportion, and is not unfrequently found to be even in excess.

The important distinction which exists between symptomatic or organic fevers, and idiopathic, or non-organic fevers, is very essential to be borne in mind, for in the former no such deficiency of the fibrin exists as we have seen to belong to the latter; the blood in inflammatory affections, as will be shown hereafter, exhibiting a state of its spontaneously coagulable element the very reverse of that which belongs to the blood of idiopathic febrile disorders. It must also be recollected, that an idiopathic fever may, during its progress, become complicated with organic lesion, a circumstance which would affect materially the amount of fibrin in the blood, its effect being to increase the proportion of that constituent.

Increase in the Amount of Fibrin in Inflammatory Affections, as in Pneumonia, Pleuritis, Peritonitis, Acute Rheumatism, SfC.

While in the class of febrile disorders, of which we have just spoken, a deficiency of the fibrin in the blood exists, in another series of affections, the inflammatory, this element is found to be in excess


To constitute an inflammation, however, two "concurrent circumstances are required; it is not alone necessary that the proportion of the fibrin should be increased, but also that an organic lesion should have occurred, these two pathological alterations bearing a close and constant relation with each other.

Since, then, the spontaneously coagulable element of the blood in the one class of disorders, viz : fevers, is deficient, while in the other class, inflammations, it is super-abundant, it follows that the specific cause which gives origin to these two orders of maladies operates in two opposite directions; its tendency in the one being to diminish, and in the other to augment the quantity of fibrin.

The law of the increase in the quantity of fibrin in inflammatory disorders manifests itself under very remarkable circumstances; such, indeed, as one would imagine to be but little favourable to its manifestation : thus, in the case of an inflammation supervening on typhus, in which we have seen that the normal scale of fibrin undergoes a depression, a disposition to the augmentation of that scale will become apparent. In the example of typhus complicated with local lesion, we have two forces in operation; the tendency of one of which is to diminish the amount of fibrin, and of the other to increase that amount; and the result of which forces operating at the same time is the production of a mean effect.

The proportion of fibrin in man in a state of health is estimated at 3 parts in every 1000 of the blood. In a case of inflammation occurring in the course of typhus, the scale was found to be h\ in persons affected with chlorosis, in which we have seen that it is the globular element of the blood which is deficient, and attacked with capillary bronchitis, acute articular rheumatism, erysipelas, and pneumonia, the proportion varied from 6 to 7 and 8; in acute inflammations occurring in healthy individuals, it oscillated between 6 and 8; and in a less number of cases, between 7 and 10. The highest scale recorded by M. Andral is 10; and this was met with only in pneumonia, and acute rheumatism, while the lowest was only 4 : this scale borders upon that which is regarded as normal, and is encountered only in sub-acute inflammations.

It is not merely, however, in pure and extensive cases of inflammation that the proportion of fibrin in the blood becomes augmented, for we find it also increased in every organic affection which is accompanied by even a slight degree of inflammation : thus in phthisis, at the period of the elimination of the tubercle, as well as in cancer, in which there is inflammation of those portions of the organs, the seat of the disease which immediately surround the tuberculous, or cancerous deposit, we have also an increased amount of fibrin in the blood. This increase, even in the last periods of the disorder in phthisis, rarely exceeds 5 parts in the 1000. The blood in consumption exhibits then not merely an excess of fibrin, but also a depreciation in the proportion of its red element to the extent shown under the heading AncBmia.

There is one condition of the system compatible with a state of health, under which also the proportion of the fibrin in the blood is augmented, and that is gestation. It is stated, however, by M. Andral, that this increase manifests itself only in the three last months of pregnancy, previously to which the scale of the fibrin is found to be slightly depreciated. This augmentation goes on increasing from the sixth to the ninth month, and is greatest at the completion of the term of utero-gestation, which fact offers a satisfactory explanation of the reason of the liability to inflammatory attacks on the part of women recently delivered. The condition of the blood, therefore, in the last periods of pregnancy is allied to that state of the vital fluid which is especially indicative of the existence in the system of an inflammation.

The characters presented by the clot in inflammation are almost the reverse of those which distinguish it in fevers. It is of moderate size, of firm texture, frequently cupped, and its surface usually covered with the buffy coating of a variable thickness. The theory of the formation of this peculiar layer has already been entered into, and the various circumstances under which it has been encountered have now been noticed ; we have seen that it occurs in two very different states of the system, that it is present on the clot of blood abstracted in ansemic conditions, as well as on that formed in blood withdrawn in inflammatory states ; in the first of these there is, in comparison with the red corpuscles, a relative increase in the proportion of the fibrin, and in the second, a positive augmentation of that important element of the blood.

The fact of the existence of a super-abundance of fibrin in the blood in inflammatory states may be in some measure inferred from the circumstance of the escape in inflammation of a portion of its fibrin, and which doubtless is attended with a certain degree of relief to the organ affected. In many cases, however, it is not alone the fibrin which escapes, and which is liable to become organized, but also the other constituents of the blood, its red and white corpuscular element, (the latter probably constituting the pus which in certain severe cases is met with,) and the serum : these constituents, however, are not susceptible of organization, and are, where recovery takes place, removed from the situation of their effusion by absorption.

The discovery of the fact, that in inflammatory disorders an excess of fibrin is formed, explains the exact manner in which blood-letting proves so serviceable, viz : by removing from the system directly a portion of its super- abundant fibrin; so powerful, however, is the cause which determines the formation of this excess of fibrin, that in spite of the most energetic and frequent use of the lancet, the scale of that element of the blood will frequently, and indeed does generally, ascend.

Condition of the Blood in Hemorrhages.

Reference has been made to the frequent occurrence of hemorrhages in two very distinct classes of disorders, the plethoric and the febrile. In the first, we have seen that it is the red element of the blood which is absolutely in excess over the other constituents of that fluid, while, in the second, it is the fibrin which is deficient, the globules being unaffected, and existing usually in their normal proportion. Thus, relatively to the fibrin in both series of affections, the globules are always in excess, in reference to the first series, the plethoric, being absolutely so, and to the latter, relatively super-abundant.

While it is this excess of the red globules which probably determines the occurrence of hemorrhages, the nature and degree of these losses of blood are modified by the amount of fibrin which that fluid contains. Thus, the character of the hemorrhages occurring in plethoric individuals is very different from that encountered in persons labouring under fever in most of its forms ; in the first, we have copious epistaxes and the effusion of blood into the substance of the brain, constituting sanguineous apoplexy; in the second, almost any tissue of the body may be the seat of the effusion ; the blood may escape from the nose, the gums, the throat, or the bowels, or it may be poured out beneath the skin in patches, constituting petechiae, which we meet with so frequently in severe cases of typhus, and in scurvy. The hemorrhages to which the plethoric are liable are for the most part salutary, while those which take place in fevers are as generally prejudicial. The treatment to be adopted in the two cases is very different ; in the one, it may be necessary to have recourse to venesection, with the view of lessening the scale of the red globules, and in the otner, such a mode of proceeding would in all probability be fatal, the object in it being to restore to the blood its normal proportion of fibrin.

The distinction which has here been dwelt upon between the hemorrhages to which the plethoric are exposed, and those to which the system is obnoxious in febrile disorders at an advanced period of their attack, corresponds with the division of hemorrhages into active and passive ; the former, or sthenic type, denoting the active, and the latter, or asthenic, the passive hemorrhages.

In disorders in which usually we have no excess of the red globules, but in which the fibrin invariably exceeds its usual quantity, as the inflammatory, and in affections in which the red element is constantly deficient, but in which the red fibrin retains its proper proportion, as in anaemic states, and especially chlorosis, we find that hemorrhages are of very rare occurrence, and hence again we are led to recognise the accuracy of the statement, that the essential conditions for the occurrence of hemorrhages are an excess of the red corpuscles, as well as in certain cases a deficiency of the spontaneously coagulable element of the bloed, viz : the fibrin.

Between the condition of the blood, in which there is a deficiency of fibrin, as in most fevers, and that state of the system which occupied so much of the attention of the ancient humeral pathologist, and which has been denominated the putrid, an exact identity exists, and the gresrter the depression in the scale of the fibrin, the more manifest does the putridity become. While the blood is still circulating within its vessels, we can scarcely conceive of its becoming putrid ; nevertheless, so great in some cases is the deficiency of fibrin, and so proportionate the consequent tendency to putridity, that even during life certain symptoms indicative of this condition become manifest, as the extreme prostration of the strength, the foetor which belongs to all the excretions, and the vital principle having escaped, the external signs of decomposition almost immediately appear.

The characters of the blood in hemorrhages scarcely differ from those which we have pointed out as belonging to it in fevers ; from the small quantity of fibrin, and the excess of red globules, we find that the clot is large, ill-formed, very soft, and never covered with the buffy coating, and that finally, in a very short time, it undergoes almost entire dissolution, the only trace of solid matter in the blood consisting of a few shreds of fibrin.

There is one disease, viz: scurvy, in which a condition of the blood, as regards its fibrin, exists analogous to that which characterizes fevers, and in which also the same tendency to repeated hemorrhages and to the formation of petechiae belongs, as is witnessed in fevers.

It is a question for consideration whether the deficiency of the fibrin referred to is the real cause of the proneness of the blood to decomposition and dissolution; and whether, if this be the case, there is not some other prior cause which leads to and regulates the extent of the diminution of the physiological standard of the fibrin.

The experiments of Magendie show that the mixture of certain alkaline substances with the blood not merely preserve it in a fluid state, but restore it to the fluid form, even after it has once coagulated. M. Magendie injected into the veins of living animals a certain quantity of a concentrated solution of the sub-carbonate of soda, and found that in the dead bodies of these animals the blood was almost entirely in a fluid state, and that even during life they presented many of the symptoms which are acknowledged to denote a state of dissolution of the blood.

The alkaline condition of the blood in scurvy, in which the proneness to hemorrhage is so great, is well known.

A fluid state of the blood is said to exist in those who have died from the bite of serpents, and it is most probable that in like manner the effect of the imbibition of a poisonous miasma is to cause the blood to retain its fluidity.

The deplorable effects which sometimes ensue from a dissectionwound are most probably due to the entrance into the blood of a poisonous matter, and in fatal cases we have all the signs indicative of a dissolution of the blood.

It is likewise asserted, that any violent impression made on the nervous system, either through the influence of some strong moral emotion, or as the result of a blow, especially on the pit of the stomach, an electric shock, as of lightning, retards, or altogether prevents, the coagulation of the blood, while at the same time it destroys life. That the same effect is likewise produced, though in a manner less obvious and less sudden, by the slow and continued operation of any cause which depresses the power of the nervous influence, so as at length to effect the health prejudicially, cannot be doubted.

The proneness of children to hemorrhages, their liability to febrile disorders, and the difficulty of restraining the bleeding which flows from any breach of continuity which the skin may have suffered, especially that of a leech-bite, in infants, are well known. The state of the blood in children is not commented upon by the talented authors to whom we have had such frequent occasion to refer in their important pathological essay on the blood; it is most probable, however, that while its globular element is somewhat in excess, that in fibrin it is equally deficient.

With one other remark we will bring this short chapter on hemorrhage to a conclusion, and proceed in the next place to consider the effect produced upon the economy by the deficiency of another element of the blood. The statistical and historical details of epidemics clearly prove that those dire forms of disease, of which extensive and alarming hemorrhages were such frequent complications, have in these latter times become much more rare. This happy result is doubtless due to the advances made in the arts and sciences, and to their more extensive application in the improvement of the hygienic condition of mankind.

Decrease in the Normal Proportion of Albumen.

It is now generally known, that the majority of cases of dropsy depend upon a pathological alteration of some solid organ of the body, as the heart and the liver; most persons are also aware of the fact that other cases of dropsy occur, which do not arise from any such morbid organic condition, but have their origin, according to MM. Andral and Gavarret, in a pathological degeneration of one of the elemental constituents of the blood.

In the dropsy which attends the advanced stages of the affection known by the name of Bright's disease of the kidney, in that which supervenes upon scarlatina, in hydropsies arising from insufficient and improper diet, as well as in those which occasionally follow suddenly suppressed perspiration, it has been observed that the urine is always albuminous, and the writers just mentioned have ascertained the existence of a fact which stands in close relation with the albuminous excess in the urine in the instances enumerated, viz : that the blood is itself in these cases, on the contrary, deficient in albumen. Trie knowledge of these two facts, therefore, and the observation that their occurrence is so generally associated with dropsical effusion, has led MM. Andral and Gavarret to entertain the opinion that a close connexion exists between the deficiency of albumen in the blood and the forms of dropsy alluded to, and which is probably that of cause and effect.

In speaking of non-organic dropsies it has, until recently, been conceived sufficient to say that they depended as a cause upon impoverishment of the blood ; but this expression we now know to be vague, inasmuch as it does not convey any exact notion of the real changes which the blood may have undergone: we have seen that the blood may be rich in its red globules or in its fibrin, and also that it may be poor in these elements in almost every proportion and degree. Let us see whether a deficiency of either of the two constituents just named predisposes to dropsies. In anaemic states, and in chlorosis especially, we have an impoverished state of the blood, and in these we know that it is the red corpuscles which are deficient; and yet daily experience shows us that dropsy in such states, and particularly in chlorosis, even in its most severe forms, is a very rare termination. In febrile disorders again, we have, for the most part, an impoverished condition of the blood, arising from the depression in the scale of the fibrin, and yet of these we do not find dropsical effusion to be by any means a frequent result.

It is not excess of water in the blood which gives rise to dropsy, for, if that were the case, then would it frequently occur in the disorder to which we have referred, chlorosis, in which a greater proportion of water than is ^normal exists in the blood.

The causes of impoverishment of the blood enumerated therefore do not act as exciting causes of dropsy : there remains but one other element of the blood, the albumen, for our consideration, and this we have seen to be constantly deficient in the blood in certain forms of dropsy, and we are therefore constrained to adopt the conclusion that this depreciation in the scale of the albumen is intimately associated with the occurrence of those forms.

It does not appear, according to M. Andral, that the albumen can undergo a spontaneous depreciation in the blood, similar to that of which we have seen that the red globules and the fibrin are susceptible ; this, if correct, is very remarkable, and hence it would follow that whenever a deficiency of the albumen of the blood exists, invariably, at the same time, the urine would be found to be albuminous, provided always that no dropsical effusion existed, the effect of some organic malady.

In most organic dropsies the diseased organs act as exciting causes of the serous effusion by the mechanical impediment which their altered structure and enlarged size present to the circulation in the vessels, and which, therefore, relieve themselves by permitting the escape of a portion of their contents. In Bright's disease, although the kidney


156 0RGAE1ZED FLUIDS.

is affected, that organ does not concur in the formation of the dropsy, except in a manner altogether indirect, and to such an extent only, as that the pathological alteration which its substance undergoes is of such a nature, as to afford greater facility to the passage of the albumen through it.

The serosity effused in cases of dropsy is not identical in its constitution with the serum of the blood ; it contains usually far less of the inorganic constituents which are held in solution in healthy serum, as well as a far less proportion of albumen, than that which belongs to serum in its normal state. The physiological standard of the albumen in the blood is eighty in every thousand parts ; in sixteen cases in which the serous effusion was analyzed by M. Andral, the scale was found to oscillate between 48 and 4, these two numbers representing the highest and the lowest proportions. In six cases of hydrocele, the amount of albumen was, as represented in the following figures, 59, 55; two of 51 ; 49, 35. It should be remarked that none of these analyses refer to cases of dropsy connected with excess of albumen in the urine. It would be interesting to ascertain the amount of the albuminous element contained in the serum effused in such cases.

MM. Andral and Gavarret state that they did not find that either the cause of the hydropsy, or its seat, excited any influence over the quantity of albumen of the effused serum; but they remarked that the amount did in some degree depend upon the condition of the constitution, and that the more robust its state, the greater the proportion of the albumen: in this way the higher scale exhibited in the six cases of hydrocele may be accounted for, their occurring in persons all of whom were young and strong ; and thus, also, the great depression of that scale may be explained in those whose constitutions have been weakened by repeated tappings.

Two explanations may be given of the reason why blood less rich than ordinary in albumen should give rise to serous effusion. The first is, that the abstraction of the albumen may alter the density of the serum, and thus permit more readily its escape through the walls of the vessels; the second is, that blood deprived of its albumen becomes less yielding, and so glides less easily along the walls of the capillary vessels, thus occasioning in them an obstruction to the circulation and consequent effusion of serum. Of these explanations, the former is perhaps the more probable.

The proportion of water in all serous effusion is, of course, considerable, and is greatest in those cases in which there is least


THE BLOOD. 157

albumen. The mean proportion of water in the serum of the blood is 790 in 1-000 parts ; in the fluid of dropsies the highest scale hitherto observed is 986, and the lowest 930.

The fluids effused in burns and scalds, and as the result of the application of a blister, and which are always preceded by some degree of inflammation, are also rich in albumen. The very curious observation is made by M. Andral, that in cases where dropsical effusion exists in more than one situation in the same individual, that in each locality the fluid effused may exhibit a very different proportion of albumen. Thus, in a woman attacked with an organic affection of the heart, there were thirty parts of albumen in the fluid of the pericardium, while there were but four parts in the serosity of the cellular tissue of the inferior extremities.

In having thus ascertained the different modifications in quantity which the three great elements of the blood may undergo — the globules, the fibrin, and the albumen — it yet must be confessed that the pathological history of the blood is still very far from being rendered complete. It is more than probable that rigorous chemical analysis will disclose the fact, that the several extractive as well as inorganic substances which exist in the blood, vary greatly in amount in the numerous disorders to which the human body is liable. From the great quantity of these substances which are found in the urine, it would appear that the grand purpose fulfilled in the economy by this excretion is that of regulating their amount in the blood, and of reducing it to a standard consistent with a physiological condition of the system.

Into this branch of the pathology of the blood inquirers have as yet scarcely entered ; and there can be no doubt but that investigations instituted in this direction would be attended by the development of many important facts.

Therapeutical Considerations.

The practical value to be attached to the various particulars related in the preceding pages on the pathology of the blood, is so obvious that it needs not to be illustrated at any great length.

The knowledge of the particular element of the blood which in any state of the system or disease may be affected, inasmuch as it discloses the chief cause of such condition or malady, furnishes the practitioner with an unerring principle upon which the nature and the extent of the treatment adopted should be founded. Hitherto, the chief guides


158 ORGANIZED FLUIDS.

in practice have been based upon experience and clinical observation; both, doubtless, of high importance; but still not in many cases sufficient to detect the cause of a malady, and therefore not in themselves equal to the determination of the exact line of treatment to be pursued, or of the extent to which that line should be followed.

We are now not merely acquainted with the bare fact, derived from experience, that in anaemic conditions of the system the different preparations of iron are useful, but we have dived deeper into the mysteries of organization, and we now know the reason why iron is necessarily so beneficial in the disorders to which such a condition of the system gives rise.

The precise objects to be held in view, in the employment of every remedial appliance in the treatment of inflammatory affections and fevers, we are now acquainted with ; and by our present knowledge we can judge of the propriety and extent of usefulness of the various plans of treatment which in times past have been had recourse to, or which still continue to be applied; and we can detect the reason why one particular mode of treatment should have been more successful than another.

Becquerel and Rodier's Pathological Researches on the Blood.

MM. Becquerel and Rodier* have traversed the same ground as MM. Andral and Gavarret in reference to the blood, which they have examined both in health and disease.

These authors confirm many of the more important results obtained by antecedent observers, but question the accuracy of some of those results, and add new facts in relation to the normal and abnormal composition of the blood.

The results which confirm those which had been previously obtained are the following:

1. The augmentation of the fibrin in inflammations, the establishment of which fact is especially due to MM. Andral and Gavarret.

2. The diminution of the globules in chlorosis, in the condition denominated the anaemic, and under the influence of fasting; a fact stated by M. Lecanu, and confirmed by MM. Andral and Gavarret.

3. The diminution of the globules from hemorrhages and anterior bleedings ; a result which, signalized for the first time by MM. Prevost

  • Gazette Medicate de Paris, 1844. "Recherches sur la Composition du Sang

dans l'etat de Sante et dans l'etat de Maladie."


THE BLOOD. 159

and Dumas, has been confirmed in the numerous analyses of MM. Andral and Gavarret.

4. The little influence of bleedings upon the scale of the fibrin.

5. The diminution of the albumen in the malady of Bright, as indicated by Gregory, Rostock, Christison, Andral and Gavarret.

Of the results which differ from, and perhaps invalidate those of antecedent observers, the principal are —

1. That the scale T VVo> given as representing the mean of the globules in a state of health, is too low, and is not the same in man and in woman.

2. That the scale representing the fibrin as T / f j is too high.

3. That there is not alone in plethora an augmentation of the globules, as signalized by M. Lecanu, and as has been admitted by MM. Andral and Gavarret.

4. That the scale of the globules is not preserved in its normal proportion in the majority of acute affections.

5. That the depression in the scale of the fibrin in severe fevers is but little constant.

The more important of the new results are the following:

1. That the scale 141 expresses the mean number of the globules in man in a state of health, and that of 127 represents the average in woman.

2. That the ordinary scale of the fibrin is 2*2, and the mean 3.

3. That in plethora there is an augmentation of the quantity of the mass of the blood.

4. That the influence of disease upon the composition of the blood is to occasion from the commencement a diminution in the proportion of the globules, and this diminution continuing during the progress of the malady, ends in the production of the anaemic condition of the system.

5. That there is an absolute excess of fibrin in many cases of chlorosis and of pregnancy, and that its diminution is far less constant than has been considered in fevers.

6. That the albumen of the blood diminishes under the influence of illness; that it is more considerable in inflammations; and further, that the diminution is in direct relation with the augmented amount of fibrin, which it may be presumed is formed at the expense of the albumen ; that there is not only a very great diminution of albumen in the malady of Bright, but also in certain affections of the heart, accompanied by dropsy, and in certain severe forms of puerperal fever.


160 ORGANIZED FLUIDS.

7. That the amount of cholesterine and of acid fats increases as we advance in age ; but that this increase is not felt until from the fortieth to the fiftieth year ; that it is also found in augmented quantities in the blood in constipated states of the system, and in jaundice, with retention of the bile and decoloration of the fasces.*

The Blood in the Menstrual Fluid.

The menstrual fluid contains all the elements of the blood, especially the red and white corpuscles, and it is therefore in the same manner as the blood itself susceptible of coagulation. In addition to the constituents of the blood, we find the uterine discharge to be composed of vaginal mucus, mixed up with numerous epithelial scales, which it has acquired in its passage along the vagina.

Unlike, however, in one respect the blood itself, which in a state of health is alkaline, the menstrual fluid is acid, its acidity arising from its admixture with the vaginal secretion.

Transfusion of the Blood.

It has been stated, and the statement is most probably correct, that between the size of the blood corpuscles and that of the capillaries of the same animal, an exact relation exists, and it is by reference to this fact that the fatal effects which have so often ensued, from the transfusion of the blood of one animal into the vessels of another, have been apparently so satisfactorily explained. The little vessels, it has been said, are too small to admit the larger globules of the new blood; a mechanical impediment is thus offered to the circulation of the blood in the capillaries, which stagnates in them, giving rise to constitutional disturbance, and ultimately to death. This explanation, plausible as it appears, has been shown by recent experiments to be erroneous, and that the true cause of the fatality which has so often attended the operation of transfusion, depends upon the difference which exists in the qualities of the fibrin in the blood of two different animals, or even of two distinct individuals ; this is shown by the fact that the transfusion of blood deprived of its fibrin is never followed by the serious results to which reference has been made. Notwithstanding this fact, it is yet very evident that if the blood of an animal, the corpuscles of which are much larger than the human blood disc,

  • The above remarks are abbreviated from an abstract of MM. Becquerel and

Rodier's work on the blood, by MM. Millor and Reiset, contained in the " Annuaim de Chimie," for 1846.


THE BLOOD. 101

and at the same time are of a different form and structure — such as, for instance, those of some birds — be introduced into the vessels of man, a very serious and probably fatal mechanical impediment would be presented to their circulation through the capillaries. Blood corpuscles' of a circular form, and but little larger than those of man, might indeed make their way through the vessels in consequence of the plastic nature of the globuline which composes them.

The new globules thrown into the system by the operation of transfusion, although they would circulate for a time with the other blood globules, would doubtless all become destroyed and removed in the course of a few days, and this especially if the blood corpuscles were different from those of the animal upon which the transfusion had been practised.

The Blood in an Ecchymosis.

When a part is bruised to such an extent as to occasion the rupture of the minute capillaries and vessels contained in it, blood is effused, constituting an ecchymosis. The same effect sometimes takes place, not as the result of the application of external violence, but from disease, the solid tissues, and that of the vessels especially, giving way through debility, and permitting the escape of their contents, as occurs in malignant and putrid fevers, in Purpura Hemorrhagica, in scurvy, and in bed-sores.

If a portion of the effused blood be removed from the bruise, and examined microscopically, the globules will be observed to be wrinkled and irregular in form ; corresponding with and depending upon internal changes in the condition of the blood effused, and which are indicative of the occurrence of decomposition, certain external appearances will be noticed ; the skin will appear mottled, different hues of black, green, and yellow being intermixed, and varying in intensity until the period of their total disappearance.

The phenomena of decomposition precede the disappearance of the red corpuscles which are removed from the seat of injury, and are returned to the circulation in a state of solution. Now, were the opinion true that the blood corpuscles are applied directly to the formation of new tissue, a very different result to the decomposition and solution of the globules, to which we have referred, would be anticipated, and we should expect to find that the extravasated blood had given rise to an adventitious and organized product, an event to which ecchvmoses never lead.

11


162 ORGANIZED FLUIDS.

The Effects of certain remedial Agents upon the Constitution and Form of the Blood Corpuscle.

We have seen, in the remarks on the effects of reagents, that many solutions and substances applied to the corpuscles, after their abstraction from the system, modify their form, appearance, and properties.

Thus we have seen that in water, as in any other analogous liquids of less specific gravity than the serum of the blood, that the corpuscles lose their normal form, and become circular, their colouring matter passing at the same time into the fluid.

We have likewise. observed that in liquids of an opposite character, and the density of which equals or exceeds that of the blood, their form is preserved, and even rendered flatter than ordinary: thus, their shape is well maintained or but slightly affected in the white of egg, urine, the saliva, concentrated solutions of sugar, of the chlorides of sodium, and of ammonium, and the carbonates of potassa and ammonia.

The blood corpuscles likewise preserve their form in the solutions of other substances, the density of which would not appear to be very great, but which are possessed of very strong and decided properties : thus, they maintain their shape well in a solution of iodine, and become but slightly contracted in that of chloride of sodium; while, according to Henle, the primitive flattened form of corpuscles, swollen by the imbibition of water, may be restored to them by the application of the concentrated saline solutions.

Nitric acid produces an irregular contraction of the corpuscles. It has been remarked in like manner that a host of substances affect the colour of the corpuscles.

But it is not alone the form and colour of the blood corpuscles which are affected by the contact of reagents; their properties also are modified by them.

Thus, the corpuscles to which iodine has been added are so hardened by it, that they experience little or no change of form on the addition of water.

The same is the case, according to Henle, after treatment by nitric acid.

The acetic, and one or two other acids, it is known, dissolve the corpuscles of the mammalia without residue, but leave almost unaffected the granular nucleus contained in the red blood corpuscles of oviparous vertebrata.


THE BLOOD. 163

The above are some of the more striking effects produced in the form, colour, and constitution of the blood corpuscles out of the system, on their treatment by reagents.

Now, there is evidence to show that blood corpuscles, while they are circulating in the body, are likewise affected, although to an extent less considerable, and therefore less appreciable, by substances and solutions introduced into the system through the medium of the lungs or of the stomach.

Thus, we know that the blood changes its colour in the lungs and during its circulation through the capillaries, and that these changes are dependent upon the relative amount of oxygen and of carbon contained in the corpuscles.

Again, it has been asserted by Schultz, as already mentioned, that, accompanying these alterations of colour, there are also changes of form, the corpuscles becoming more or less circular in carbonic acid and hydrogen gases, and flat in oxygen gas. This assertion I have myself failed to verify.

It cannot be doubted, however, but that the form of the red blood corpuscle must vary according to the variations of density experienced by the liquor sanguinis, and further but little hesitation can be felt in admitting that this alteration of density does really attend upon particular conditions of the system ; thus, in inflammatory affections, the liquor sanguinis is assuredly more dense than it is in states in which an opposite condition of the blood exists, that in which the watery element abounds.

After very copious imbibition of water, also, it can scarcely be doubted but that the density of the blood is lessened, and that the red corpuscles are modified in shape in consequence.

Thus much for colour and form ; let us see if we are acquainted with any fact capable of proving that the constitution of red blood corpuscles is also influenced by the introduction into the stomach of remedial agents.

Schultz relates the fact that the corpuscles of the frog, in the mouth of which during life iodine had been placed, resisted for a longer time the action of water.* The truth of this most interesting and important observation I have myself verified.

The blood corpuscles of a frog, which were subjected to the vapour of iodine, underwent no appreciabe change of form in water for nearly an hour during which they were observed, a time more than

  • Das System der Circulation. Stuttgard, 1836, p. 19.


164 ORGANIZED FLUIDS.

sufficient to ensure the complete change of shape and subsequent disintegration of the blood discs of a frog not similarly treated.

It may be observed that in the case related, starch failed to detect the presence of iodine, although this was set free by previously dissolving the corpuscles by means of acetic acid.

After the relation of the above facts, it is evident that remedial agents do affect in several important particulars the blood corpuscles of the living animal, and it is further probable that a considerable proportion of their remedial influence is dependent upon the nature and extent of their power in modifying the red blood disc.

The Importance of a Microscopic Examination of the Blood in

Criminal Cases.

In criminal cases it is sometimes a matter of the highest importance to the furtherance of the ends of justice, that the nature of certain stains, observed on the clothes of an accused person, should be clearly ascertained.

The fact usually to be determined is, whether the stains in question are those of blood or not. Now, in the decision of this important matter, the microscope comes to our aid in a manner the most decisive and convincing.

If the stain be a blood stain, and if its examination be properly conducted, the microscope will lead to the detection in it of the blood corpuscles themselves, both white and red.

The inquiry having been proceeded with thus far, and the stain having been proved to be one formed by blood, it still remains for decision, whether the blood thus detected is human or not.

In the solution of this difficulty the microscope likewise affords considerable assistance, and this of a kind which can be obtained in no other way. Although by this instrument we are not able to assert positively from an examination of the blood stain itself, free from admixture with any other organic material, that the blood is really human, we yet shall have it in our power very frequently to declare the converse fact, viz : that a certain blood stain is constituted of blood which is not human, a particular on the knowledge of which the life of an accused individual might depend.

Thus, if we find that the blood globules are of a circular form, and destitute of nuclei, we may safely conclude that they belong to an animal of the class Mammalia, although, at the same time, we in all probability should not be able to pronounce upon the name of the


THE BLOOD. 1G5

mammal itself; if, on the contrary, the blood corpuscles are elliptical, and provided with a granular nucleus, we may be equally certain that they do not appertain to that class, but either to the division of birds, fishes, or reptiles.*

By the size also as well as the form of the corpuscles, some idea of the animal from which the blood was derived might be formed ; and if we cannot pronounce with certainty upon this, we shall at all events, and at all times, be able to go the length of affording negative evidence, and of asserting that the corpuscles do not represent the blood of certain animals which might be named, and a knowledge of which fact might prove of extreme importance.

To show the valuable nature of the evidence which it is in the power of a medical man who makes a right use of the microscope frequently to afford, in criminal inquiries, we will suppose the following case:

A person is apprehended on the suspicion of having been concerned in a murder. On his clothes are observed certain stains; upon these he is questioned; he admits that they are blood stains, and states that he had been engaged in killing a fowl, and that in this way his clothes had acquired the marks. The stains are now submitted to microscopic examination ; the blood of which they are constituted is found to belong to an animal of the class Mammalia, and not to that of Aves; discredit is thus thrown upon the party suspected, fresh inquiries are instituted, fresh discoveries made, and the end of all is the conviction of the accused of the crime imputed.

But a third question presents itself, to which it is very necessary that a satisfactory reply should be made, viz : did the blood, of which the stain is constituted, flow from a living or dead body? This query we will proceed to answer.

If a vessel be opened during life, or even a few minutes after death, the blood which issues from it in a fluid state will quickly become solidified from the coagulation of the fibrin.

But if. on the other hand, a vessel be opened some hours after death, the fluid blood which escapes will not solidify because it contains no fibrin, this element of the blood having already become coagulated in the vessels of the body in which it still remains.

Now, this act of the solidification of the fibrin is deemed by many

  • The only animals of the class Mammalia which have blood corpuscles of an

elliptical form, are those of the order Camelidcc ; they are, however, very small, and destitute of nuclei.


166 ORGANIZED FLUIDS.

to be a vital act, and to be the last manifestation of life on the part of the blood.

It would appear, however, that the coagulation of the blood should not be regarded as a vital act, seeing that blood which has been kept fluid for some time by admixture with saline salts will coagulate when largely diluted with water, and also, that blood which has been frozen previous to coagulation will undergo the process of solidification after it has been rendered fluid again by thawing.*

Presuming, then, that the coagulation of the blood is not an act of vitality, the inference to be deduced from the presence of coagulated fibrin in blood stains, in which the corpuscles may be detected, is scarcely weakened thereby, since the finding of such fibrin in such a situation, and in connexion with the blood corpuscles, scarcely admits of a rational and probable explanation of its occurrence being given apart from the idea that the blood had issued from a body either living or but just dead, and in which coagulation of the fibrin in the vessels had not occurred.

The blood stains, therefore, which contain coagulated fibrin in them, it is but little doubtful, must have proceeded either from a living individual, or from one but just dead ; while, on the contrary, it is as little to be doubted, but that those stains which do not contain solidified fibrin, must have emanated from a body dead some hours, or from blood which had already been deprived of its fibrin.

From the disposition and form also of the blood spots, some idea can be formed as to whether the blood had sprit out of a living body or not.

A few observations may now be made, first, on the length of time after the formation of blood stains at which the corpuscles can be detected ; and second, on the best mode of proceeding in the examination of those stains.

From observations which I have made, it would not appear that it is necessary that the blood stain should be recent. I am inclined to think that the period scarcely admits of limitation.

Thus in blood stains six months old, I have observed the corpuscles presenting very nearly the form and appearance proper to them when recently effused, and previous to their becoming dried up.

In the blood of the frog, six months after its abstraction from the

  • Dr. Polli has related a case in which the complete coagulation of the blood did

not take place until fifteen days after its abstraction. — Gazzetta Medica di Milando, 1844. ■


THE BLOOD. 167

animal, I have observed the corpuscles, both red and white, and in the former, the characteristic granular nuclei with so much clearness, that it would have been an easy matter to have studied upon them the development of blood corpuscles.

The observance of one precaution, at least, is necessary for the successful exhibition of the microscopic characters of blood stains.

Thus, water should never be applied to them, nor indeed any other fluid, the density of which is less than that of the serum of the blood, for all such liquids will occasion the discharge of the colouring matter of the blood corpuscles and an alteration of their form ; thus the circular but flattened corpuscles of the Mammalia will assume a globular shape, as will also the elliptical blood discs of birds, fishes, and reptiles ; one of the greatest points of difference between the blood corpuscles of the former and latter classes being thereby effaced.

Blood stains, therefore, should be moistened, previous to examination, with some fluid, the density of which nearly equals that of the liquor sanguinis; and I have found the albumen of the egg to preserve the form of the corpuscles excellently well.

Failing, however, in detecting the blood corpuscles, a result scarcely to be anticipated, assistance may be derived from a toxicological examination of the blood.

The only tests peculiar to the blood are those which have relation to the haematine. This principle it would, however, be difficult to obtain from blood stains in sufficient quantity for the purposes of copious chemical analysis.

Nevertheless, corroborative evidence of the suspected character of a stain might be obtained by its general chemical analysis, and which should be treated as follows:

The stain should first be moistened with cold distilled water; as much of the matter of it should then be removed as possible, and placed in a test tube with an additional quantity of water. This being agitated, the colouring material, if the stain be a blood stain, will be dissolved by the water, imparting to it a pinkish colour, while, provided the blood flowed from the body during life, or at all events within a few minutes of decease, suspended in the liquid, will be seen shreds of fibrin.

This solution, when heated to near the boiling point, will become turbid, and deposit flakes of albumen.

The same thing will occur when it is treated with nitrate of silver or bichloride of mercury.


168 ORGANIZED FLUIDS.

The addition of a strong acid or alkali turns the colouring matter of a brown tint.

These results, however, are common to other mixtures of animal substances in combination with colouring matter besides the blood, and no one of them is perfectly characteristic.

It would therefore appear that the microscope is capable of revealing evidence much more satisfactory in reference to the nature of blood stains, than that which it is possible to derive from chemical examination.

Finally, it may be observed, that during the examination of blood stains, other substances may be detected in connexion with them, the presence of which would reveal not merely their nature, but also the seat from which the blood forming them had flowed ; thus, some of the various forms of epithelial cells and of hairs, may occasionally be encountered in them.

We now bring to a conclusion this long article upon the grand formative fluid of the system, the blood, and pass to the consideration of other fluids of the economy, viz : pus and mucus.


THE BLOOD. 109


PREPARATION.


[Fresh blood may be examined by placing a very small quantity on a plain glass slide, thinning it with a little serum, and quickly covering it with a piece of thin glass. The object is then ready for examination, and will require a power of 600 to 650 diameters, to well define its corpuscles. The different reagents may then be introduced by means of a pipette : the most striking in their effects, are water, acetic acid, nitric acid, and alcohol.

Perhaps the most marvellous sight that the microscopist can behold, is that of the circulation of the blood. For this purpose, the frog is usually selected, and instructions have already been given for preparing the tongue, so as to show this phenomenon.

There are other portions of the frog in which the circulation may be readily seen ; one of these is the transparent part of the web of the hind feet. In this manipulation, the body of the frog is to be secured to the frog-plate, by means of a narrow bandage or piece of tape. Those who do not possess a frog-plate, may readily make one by taking a piece of thin board about six inches long, and three inches wide; in this, a hole an inch square is to be cut near one end. The frog, secured in the bag, is tied to the solid part of the thin board, in such a manner that the web of the foot may be brought over the hole. The foot is then stretched out to the utmost, and fastened in this condition by means of strings tied to the toes, and secured to small pegs, or tacks, driven in at the margin of the board. Another method of securing the web in a state of tension, is by means of pins run through the toes, and fastened to the board. The plate, when ready, is placed upon the stage of the microscope, and the web may be examined by means of a power from 50 to 100 diameters. Any very transparent part may be examined with a much higher power, even to 670 diameters. The web should be kept moist with clear water.

Mr. Quekett observes, (page 339) " A frog so mounted, is capable of exhibiting many of the effects of inflammation ; if, for instance, a spot in the web be touched with the point of a needle, or a small drop of alcohol, or other stimulating fluid be placed upon it, the circulation will stop in that part for a longer or shorter period, according to the amount of injury inflicted ; the vessels in the neighbourhood will soon become turgid, and even sometimes be entirely clogged up with blood; if no further stimulus be applied, they will be seen to rid themselves of their contents as easily as they became full, and after a time, the circulation will be restored in every part. For those who are unacquainted with the parts which may be observed with the microscope, in the foot of the frog, it may be as well here to state, that the majority of vessels in which the blood is seen to circulate, are veins and capillaries; the former may be known by their large size, and by the blood moving in them from the free edge of the web towards the leg ; also, by their


170 ORGANIZED FLUIDS.

increase in diameter in the direction of the current ; the latter are much smaller than the veins, and their size is nearly uniform ; the blood also circulates in them more quickly. The arteries are known by their small size, and by the great rapidity with which the blood flows in them ; they are far less numerous than either of the other vessels, and, generally speaking, only one can be recognised in the field of view at a time ; in consequence of their being imbedded deeper in the tissues of the web than the other vessels, the circulation cannot be so well defined as in the latter. The black spots of peculiar shapes that occur in all parts of the web, are cells of pigment, and the delicate hexagonal nucleated layer, which, with a power of one hundred diameters, can be seen investing the upper surface of the web, is tesselated epithelium."

If the lung or mesentery of the frog be desired for exhibition, and they will both be found to display the most beautiful sight that can be conceived, the following method must be adopted : The frog must be dipped in water, at about 120° temperature; this heat will destroy muscular action, but will not suspend the circulation. The animal is then to be opened, and the lungs full of air will protrude ; one of these is bent over on a plain glass slide, and may be then viewed with a low power. The mesentery may be dissected out, and viewed in the same way.

When the tad-poles of the water-newt and frog can be found, and they are abundant in the latter summer and early fall months, the tails of these little creatures afford beautiful views of the circulation. No further preparation is necessary than enveloping their bodies in bibulous paper, leaving their tails to project ; they are then placed on the stage of the microscope in a watch-glass or live-box, and without any pain or injury to the animal, may be observed for hours, by keeping the bibulous paper moistened with water.

PEESEEYATION.

The blood corpuscles may be readily preserved for future examination, by placing a small quantity of fresh blood on a plain glass slide, and rapidly passing the slide backwards and forwards, so as to dry the blood as soon as possible. The corpuscles will then be found to be but little altered in form ; they are then to be covered with a piece of very thin glass, which must be cemented down with gold size, taking care to paint on a very thin layer at first, and a thicker one afterwards, when the first has become dry. Blood corpuscles, so preserved, will keep for years. They may also be preserved in the flat cell, with Goadby's A-2 solution, or in a weak solution of chromic acid, care being taken that the cell be tightly sealed.

Specimens of the blood of many birds, fishes, reptiles, and mammalia, may be readily procured, and when preserved in the manner already described, will form objects of great interest.]

Article III. — Mucus

We have seen that the blood consists of two parts, the one fluid, the liquor sanguinis, the other solid, the globules ; the same constitution belongs also to mucus as well as to some other of the animal fluids, as, for example, pus and milk.

Mucous globules find their analogue in the white corpuscles of the blood, while the fluid portion of mucus resembles closely the fibrin of the blood, fibrillating or resolving itself into fibres in the same manner as the fibrin. From this fact there can be no doubt but that the transparent or fluid constituent of mucus is mainly composed of fibrin.

It is probable that the fluid portion is the only essential constituent of mucus, and that the globules are connected with it merely in an indirect and secondary manner, notwithstanding that their presence is all but constant. The correctness of this view is in some measure sustained by the fact, observed first by M. Donne, that the mucus obtained from the neck of the uterus, in young girls, is invariably free from corpuscles.

It is with the solid particles of the mucus that we shall be chiefly occupied, for they more properly enter into the domain of the microscope; the fluid element eludes to a great extent the power of this instrument, and the detection of its properties enters principally into the province of the chemist.

GENERAL CHARACTERS.

Healthy mucus, in its fluid state, is a transparent, viscid and jellylike substance, which does not readily become putrescent; in its dried condition, it assumes a dark appearance, and a horny and semiopaqe texture ; in water it swells up, reacquiring most of the properties which characterized it when recent. It sometimes exhibits an acid, and sometimes an alkaline reaction, according to the exact structure of the mucous membrane by which the mucus is itself secreted.

Mucous membranes, therefore, as might be inferred from the concluding passage of the preceding paragraph, do not all present a constitution precisely similar the one to the other ; and on their differences of organization a division of them into three classes may be instituted, as has been pointed out by M. Donne.


172 ORGANIZED FLUIDS.

The first class of mucous membranes comprises those which are contiguous to the outlets of the body, and which are to be regarded • as extensions of the skin, participating in all its properties: thus, the fluid secreted by this class of mucous membranes manifests, like that of the skin, an acid reaction, and the same epithelium which invests the latter belongs also to the former; in other respects the correspondence is likewise exhibited, the membranes under consideration manifest the same sensibility, the same freedom from hemorrhage, which characterize the skin; they in like manner ulcerate less readily, and are never furnished with the vibratile cilia which belong to the second class of mucous membranes, viz : the true. This first-described class of membranes may be denominated false mucous membranes; and, as an example of it, the vagina may be cited.

The membranes which belong to the second class are situated more internally than the last, and have scarcely any thing in common with those of the first class : the mucus secreted by them constantly exhibits an alkaline reaction, and the. epithelium which invests them is of a totally different structure, the cells which constitute it being cuneiform, and in some situations provided with numerous vibratile cilia: the general properties of this class of membranes are also opposed to those of the previous division: thus, they are but little sensitive to the touch, are frequently the seat of hemorrhages, and ulcerate with much facility. The membranes of this class are to be considered as the true mucous membranes, and that which lines the trachea and bronchi may be instanced as the type of this class.

The third class is more artificial than the two preceding ; the membranes which it comprises exhibit in a greater or less degree the characters of each of the divisions already described, between which they are intermediate in situation, as in structure, participating in the characters of the false or true mucous membranes more or less, according to the preponderance of either of these classes. The membranes of this division may be called mixed, and those of the mouth and nose may be regarded as typical.

Now, however useful for the purposes of description the above classification may be, it must still be remembered that it is, to a very considerable degree, arbitrary ; the membranes which we have described as false mucous membranes belong rather to the skin than to true mucous structure, while the mixed membranes exhibit only the gradual transition from the external skin to the internal true mucous membrane: thus, strictly speaking, there is but one class of mucous


mucus. 1 73

membranes, and that the true. Corresponding with the differences which have been pointed out as characteristic of the three classes of mucous membranes, there are others appertaining to the mucus secreted by each of these orders of membranes, and which arise from their diversity of structure, and which serve to distinguish the mucus of the one class from that of each of the other classes.

1st. The mucus proceeding from true mucous membranes is viscous and alkaline, containing, imbedded in its substance, numerous spherical, semi-transparent, and granular corpuscles of about the 2 2V0 °f an mcn m diameter (see Plate XL fig. 1),* having a somewhat broken outline, as well as occasionally epithelial cells more or less cuneiform, and sometimes, provided with cilia. These corpuscles are for the most part nucleated, they are not at first soluble in water, but swell up in that fluid to two or three times their former dimensions (see Plate XI. fig. 3), and, like the white globules of the blood, to which they bear the closest possible resemblance, they contract somewhat under the influence of acetic acid, and are soluble in a concentrated solution of ammonia.

2d. The mucus secreted by false mucous membranes, or those which are analogous to the skin, although more or less thick, does not admit of being drawn out into threads, is acid, and, in place of spherical globules, contains numerous scales of epithelium, which differ from true mucous globules in their much larger size, flattened form, and in their irregular and very frequently oval outline: these scales, like the true mucous corpuscles, are nucleated, and the nuclei comport themselves with chemical reagents, in the same manner as the globules of mucus.

Example: — the mucus of the vagina. (See Plate XII. fig. 1.)

3d. The mucus proceeding from the mixed or transition membranes is sometimes acid, sometimes alkaline, at others neutral, and contains a mixture of true mucous corpuscles and epithelial scales, the relative proportion of each of which varies according to the exact structure of the membrane by which it is furnished. (See Plate XII. fig. 2.)

These divisions of the mucus into three different kinds, although to some extent artificial, as already observed, are yet not without their practical utility.

  • A law having reference to size, and the importance of which will be hereaftef

demonstrated, may here he announced. It is that the several structures, especially the corpuscular ones, entering into the composition of the animal organization, hear a near relation of size the one to the other.


174 ORGANIZED FLUIDS.

The microscopical and chemical characters of mucus likewise vary much, not merely according to the general organization of the membrane by which it is secreted, but also in accordance with the condition of the membrane itself, with the degree of irritation or inflammation to which it is subject, and with the precise nature of the disorder by which it is affected ; thus, sometimes, the mucus secreted by the lining membrane of the nose is thin and watery, the fluid element being in excess, and at others it is thick and opaque, its solid globular constituents super-abounding. Its colour also as well as its consistence exhibits various modifications in pathological states, being sometimes white, greenish or yellow.

The description of the different forms of epithelial cells alluded to, and which are occasionally encountered in the mucus mixed up with true mucous corpuscles, belongs not to the fluids, and will be given in detail under the head of Epithelium, in that division of the work which is devoted to the consideration of the solids of the human body; the structure, form, size, properties and nature of the true mucous corpuscles may here be described with advantage.

MUCOUS CORPUSCLES.

Structure. — The mucous corpuscles, which are colourless, and mostly of a circular form, are each constituted of a nucleus, an envelope, an intervening fluid substance, and numerous granules, which are diffused generally throughout the entire of the corpuscles, being contained within the cavity of the nucleus, in the space between this and the outer envelope, and, lastly, in the substance of the envelope itself; this arrangement imparting a granular texture to the entire corpuscle. (See Plate XL)

The nucleus, like the corpuscle itself, is a circular body of about one-third, or one-fourth its size : it sometimes occupies a central, but very frequently an eccentric position in the mucous globule : it is not at all times visible, although very generally so, without the addition of reagents, the best being water and acetic acid.

The addition of water to mucous corpuscles discloses, in the majority of them, but a single nucleus (see Plate XI. Jig. 3) ; in some, however, two and even three or four nucleoli appear, these resulting from the division of the substance of the single primary nucleus. 1 The effect of a weak solution of acetic acid is the same as that of water, except that an additional number of corpuscles are seen after its application to possess the divided nucleus, while in others the


mucus. 175

single nucleus is observed to be oval, and occasionally contracted in the centre — this form being the transition one from the single to the double nucleus. (See Plate XJ.fig. 4.)

If undiluted acetic acid be used, then all the corpuscles will present a compound nucleus, consisting of two, three, four, or five nucleoli, the usual number being two or three; the investing membrane at the same time under its influence loses its granular aspect, and appears transparent and smooth. (See Plate XI. fig. 5.)

The formation of these nucleoli maybe thus explained : — The effect of acetic acid is to contract the entire corpuscle ; on the nucleus, however, it would appear to operate with such force as to occasion a complete division of its substance.

The divided nucleus has been observed by many observers in the pus globule, but its occurrence in the mucous corpuscle has not been generally noticed; this division of the nucleus has been considered to constitute an exception to the law of the development of a cell around a single nucleus ; whether it ought to be so regarded is doubtful, seeing that these multiplied nuclei are usually the result of the operation of a powerful reagent, and are but rarely visible, unless as the consequence of the application of some reagent.

Mr. Wharton Jones has endeavoured to meet this conceived exception, by supposing that the nucleoli are all enclosed within the membrane of the nucleus. I have myself, however, failed to detect the existence of any envelope surrounding the nucleoli.

Form. — The form of the mucous corpuscle, although usually spherical, is subject to considerable variety, this depending frequently upon the density of the fluid in which it is immersed, but occasionally also upon the amount of pressure to which it may be subjected.

Thus, in fluid which is very dense, the operation of exostosis is set up between the corpuscle and the fluid medium which surrounds it, whereby a portion of its contents passes into that medium, as a consequence of which its investing membrane collapses, and exhibits a variety of forms. (See Plate XI. fig. 2.)

Corpuscles thus affected nevertheless retain the power of reassuming the form which properly belongs to them when they are immersed in Water or any other liquid, the density of which is less than that of the fluid contained within the cavity of the corpuscle itself. (See Plate XL fig. 3.)

The form of the mucous corpuscle is also subject to alteration from another cause, viz: pressure. Thus, it is often seen to be of an oval


176 ORGANIZED FLUIDS.

form in thick and tenacious mucus; this shape results from the pressure exercised upon the corpuscles by the almost invisible fibres into which the fluid part of mucus resolves itself, and which often become drawn out in the adjustment of the mucus on the port-object of the microscope. (See Plate XII. Jig. 3.)

The oval shape thus impressed upon it is permanent, because the pressure of the fibres of the solid mucus ceases not to act: if the pressure, however, be direct, and the corpuscle be. immersed in a thinnish fluid, it will resume the spherical form, the compressing force being removed, owing to the elasticity with which it is endowed.

Size. — The size of the corpuscle is also liable to much variation, this resulting mainly from the condition of the fluid, as to density, in which it is immersed.

Thus, in water, or any other fluid, the density of which is less considerable than that of its contents, the corpuscle imbibes by endosmosis the liquid by which it is surrounded, to such an extent as to cause it to exceed, by two or three times, its former dimensions. (See Plate XI. Jig. 3.)

By reference, then, to the two particulars referred to, viz: the density of the medium in which it dwells, and pressure, we are enabled to explain all the varieties of form and size which the mucous corpuscle presents.

Properties. — From the preceding remarks on the structure, form, and size of the mucous corpuscle, we perceive that in all these particulars, it accords closely with the white corpuscles of the blood; we shall now proceed to show that there are other points of resemblance between the two organisms.

Thus reagents affect mucous corpuscles in a manner precisely similar to that in which they act upon the white globules of the blood; water causes them to increase in size, acetic acid contracts them somewhat, and renders the nucleus and the molecules more distinct. Between mucous corpuscles and the white globules of the blood there is, then, a structural identity ; but let us see if there be not also a Junctional correspondence.

NATURE OF MUCOUS CORPUSCLES.

Mr. Addison* conceives "that mucous and pus globules are altered colourless blood-corpuscles," from which opinion it is evident that gentleman believes that the white corpuscles of the blood pass normally

  • Transactions of Prov. Med. and Surg. Association, vol. xii. p. 255.


mucus. 177

through the walls of the blood-vessels, although he does not appear satisfactorily to have witnessed the exact manner of their escape.

The perfect identity of organization existing between the colourless corpuscles of the blood and mucous and pus globules, would predispose the mind to adopt that view as sufficient and correct, which endeavoured to prove that they all had a common origin in the blood.

It must nevertheless be remembered that the notion of the identity in origin of the mucous and pus globule with the colourless bloodcorpuscle, rests upon the single supposition that the latter does really escape from the blood-vessels, in which originally it is formed.

It seems to me, however, that this statement, to which I was myself at one time disposed to attach some importance, may be fairly challenged, seeing that the direct passage of the white corpuscles of the blood appears never to have been clearly witnessed.

Moreover, the idea of any such escape of the white corpuscles is opposed to that view which reasoning alone w T ould lead one to entertain; thus, if the colourless corpuscles of the blood possessed the power of escape from their vessels, no good reason could be advanced why the red globules should not also pass through them.

If the capillary vessels terminated by open mouths, which we know that they do not in their normal state, then indeed it would be highly probable that mucous and pus corpuscles were the white corpuscles of the blood, escaped from the vessels.

I am disposed, then, to question the accuracy of the view entertained by Mr. Addison, and to believe that the globules of mucus are formed externally to the blood-vessels; the mucous glands or crypts which are scattered so abundantly over the surface of all mucous membranes, having a considerable share in their formation.

That the mucous-bearing glands are intimately connected with the development of mucous corpuscles seems proved by the fact, that the fluid expressed from them is filled with corpuscles of a smaller size than ordinary mucous globules, and destitute of any admixture with epithelial scales; these corpuscles certainly could not have found entrance into the cavities of the glands from without. (See Plate XL ^.6.)

The opinion that the mucous corpuscles are formed externally to the blood-vessels, is also supported by the observations of M. Vogel, who remarked that the plastic exudation which covers the surface of a recent wound contains, at first, only minute granules : these after a time become associated in two's and three's, and surrounded by a

12


178 ORGANISED FLUIDS.

delicate envelope; finally, fully-formed mucous or pus corpuscles appear in the liquid.

Henle believes that the white corpuscles of the blood, of lymph and of chyle, as well as those of mucus and pus, are elementary cells ; and he says of the pus corpuscles that they are nothing else than elementary cells in process of being transformed into those of the tissue which the organism regenerates in the injured part; and of the white globules of the blood he writes, they are, without the least doubt, transformed into blood corpuscles.

This opinion of Henle accords closely with that of Addison, who believes, as already stated, that out of the white globules of the blood, all other corpuscles met with in the body are formed, the former escaping from the blood-vessels.

I also regard the white corpuscles of the blood as elementary or tissue cells, although at the same time the views entertained by myself respecting them differ from those both of Henle and Addison. Thus, I do not consider, with the former, that the colourless corpuscles are transformed into red blood discs, nor with the latter, that every other cell met with in the animal organism, proceeds from the white corpuscles of the blood.

The white corpuscles of lymph, chyle, and blood, I conceive to be transformed into the epithelial cells, which constitute the epithelium with which the internal surface of the vessels of the entire vascular system is provided.

The corpuscles of mucus I conceive to have an origin distinct from the colourless globules of the blood ; but in like manner I regard them as elementary or tissue cells, believing that they are finally developed into the different forms of epithelium encountered upon the surface of mucous membranes.

The corpuscles of pus are also elementary cells and mostly altered mucous corpuscles.

The view just expressed as to the nature of the white corpuscles of the blood, is one which has but recently impressed itself upon my mind. It is not opposed, however, to the opinion previously put forth of the connexion existing between these corpuscles and nutrition, seeing that, whether in their early stage of development as colourless blood globules, or in the more mature condition of their growth as epithelial scales, they are doubtless to be regarded as secreting organs, and as effecting some important change in the constitution of the liquor sanguinis.


mucus. 179

The only respect in which the opinion that the colourless globules of the blood are converted into the scales which "constitute the lining epithelium of the vessels is at variance with a previously-expressed view, is in relation to the escape of those globules as a usual occurrence; an opinion of Mr. Addison, in which I was formerly disposed to concur, but which I am now inclined to reject.

A final reason which may be stated for disbelief in the identity as regards the origin of the colourless corpuscles of the blood and mucous globules, is the difficulty, not to say impossibility, of explaining how these colourless corpuscles, having precisely the same form and origin in the commencement, should, in one situation, be developed into a shape and a structure so totally dissimilar to that which the same corpuscles in another position exhibit, the varieties of form and structure of epithelial scales into which the white corpuscles are supposed to be developed being so considerable.

Mucous globules, then, are to be regarded as young epithelial scales, as are also the colourless globules of the blood; they both have a like structure and a corresponding function to perform, but they have a different origin; thus, the mucous globules are developed externally to the lymphatics and blood-vessels, while the colourless blood corpuscles are formed within those vessels.

The further consideration of the ulterior development of mucous corpuscles, or young epithelial cells, will come more appropriately under the head of Epithelium.

Blood corpuscles not unfrequently occur mixed up with mucous globules, as in the mucus thrown off during parturition (see Plate XII. jig. 1), and as in the rust-coloured expectoration of Pneumonia.

THE MUCUS OF DIFFERENT ORGANS.

After the threefold division of mucus which we have given, founded upon the structure of the membranes by which it is secreted, and after the description which has been entered upon of the peculiarities appertaining to the mucus of each of those divisions, it will be unnecessary to enlarge at any length upon the characters presented by the mucus secreted by the membrane which belongs to each particular organ or part; it will be sufficient just to enumerate the names of the membranes by which each description of mucus is furnished, and to point out any peculiarities which the mucous secretion of any particular organ may present: this having been done, and the distinctive characters of the three forms of mucus having been


180 ORGANIZED FLUIDS.

recalled to mind, we shall then be in a position to assign to the mucus of each locality its principal characteristics.

Thus, the mucus furnished by the nasal and bronchitic mucous membranes, and which may be called nasal and bronchitic mucus, as also that of the digestive tube, from the pyloric orifice of the stomach unto near the termination of the rectum (the caecum alone excepted), of the urethra, prostatic gland, vesiculae seminales and the uterus, belongs to the first division of mucus, viz : that which is secreted by the true mucous membranes. (See Plate XII. fig. 3.)

The mucus of the vagina presents the best example of the mucus of the second class, which is secreted by the false mucous membranes. (See Plate XII. fig. 1.)

Lastly. The mucus of the mouth, rectum and bladder, appertains to the third description of mucus, and which is supplied by the mixed mucous membranes. (See Plate XII. fig. 2.)

Vaginal and Uterine Leucorrhea.

One practical result arising from the discrimination of mucus into different kinds may here be alluded to ; thus, by means of the difference in the microscopic characters of the mucus secreted by the uterus and that furnished by the vagina, it is in our power to decide, in cases of leucorrheal discharge, whether the affection has its seat in the mucous membrane of the uterus or in that of the vagina. The mucous membrane of the uterus, as we have seen, belongs to the class of true mucous membranes ; that of the vagina, on the contrary, to the false mucous membranes. Now, if the leucorrhea be uterine, the discharge will present the globules characteristic of the secretion produced by the class of true mucous membranes ; if, on the other hand, it be vaginal, the mucus will contain the epithelial scales which belong to the mucus of false mucous membranes; moreover, the former mucus will be alkaline, and the latter acid.

Effect of Acid Mucus on the Teeth.

The degree of acidity presented by the mucus of the mouth varies considerably, according to the relative proportions of mucus and saliva which exist in the mouth at the time at which the reaction of its secretions is tested, and which proportion differs both at differen' times of the day and in different states of the system, and especiallj of the stomach. The mucus of the mouth we know to exhibit ir states of health an acid reaction, while the saliva, on the contrary,


MUCUS. 181

manifests an alkaline constitution ; the tendency of these two fluids is therefore to produce a neutral secretion, and this explanation will account for the opposite results which have been obtained by different observers. The best time to ascertain the chemical reaction of the buccal mucus is in the morning, when there is an accumulation of it on the tongue and around the gums; and the best method of determining the acid or alkaline qualities of the saliva, is first to scrape the tongue well, and as far as possible free the mouth of mucus, and then proceed to test the saliva as it issues from the orifices of its ducts. A highly acid condition of the mucus of the mouth is assuredly productive of injurious effects upon the teeth. Although this state of the buccal mucus cannot be regarded as giving rise to the peculiar caries to which the teeth are so remarkably liable; nevertheless, it cannot be doubted that it predisposes the teeth to this affection, and that it hastens greatly the progress of the decay when once this has commenced. To correct the condition of the stomach, if it be faulty, the internal administration of alkalies should be had recourse to; and to remedy the local acidity, tooth powders, composed principally of of some alkaline carbonate, should be employed.

The Vaginal Tricho-Monas.

M. Donne has discovered in the vaginal mucus of women labouring under discharges, either specific or otherwise, a new species of human parasite belonging to the order of Infusoriae. This animalcule, owing to its resemblance to the spherical mucous globules with which it is constantly associated, is with difficulty discoverable by those who are not practically familiar with its appearance, and the mode of detecting it. Thus, it presents nearly the same size, form, granular structure, and colour as the mucous corpuscles alluded to; it is to be distinguished from these, however, by the independent locomotive power which it possesses, the movements which it performs being produced principally by means of a long lash or cilium with which its anterior extremity is furnished, and the presence of which causes the animal to lose somewhat its circular contour, and assume a form approaching the oval ; in addition to this long cilium, three or four other shorter cilia exist, which surround the mouth, and which can only be satisfactorily detected when the motions of the animalcule become somewhat retarded. (See Plate XII. fig. 6.) In order that it may be seen alive and in active movement, it is necessary that the mucus containing it should be submitted to examination as soon as


182 ORGANIZED FLUIDS.

possible after its removal from the vagina; the animal once dead, it is then almost impossible to distinguish it from a mucous corpuscle.

M. Donne, on first discovering this parasite, was for some time in doubt as to whether its occurrence was to be regarded as having any connexion with the specific disorders of which the vagina is sometimes the seat, and he has at length arrived at the conclusion that no such relation as that suspected exists, and that any inflammation, specific or otherwise, sufficiently active to give rise to the secretion of puriform matter, may be accompanied by the tricho-monas which has been described.

In addition to the positive characters which have been indicated, denoting the presence of this animalcule, there is another altogether indirect which serves to signalize its existence in the vaginal mucus, and this is the presence in it of air-bubbles, which are not encountered in healthy mucus.

Vaginal Vibrios.

The tricho-monas is not the only animalcule which lives in the mucus of the vagina; there are frequently met with in it minute vibrios, which, to be satisfactorily seen, require to be viewed with a magnifying power of not less than the ji ? of an inch.

In the same manner as the tricho-monas, they always occur in connexion with pus globules ; they are not, however, any more than the tricho-monas, to be regarded as indicating the existence of specific or venereal affections, although they are not unfrequently met with in the secretion of chancres of an undoubtedly specific character.


Article IV. - Pus

GENERAL CHARACTERS.


Healthy, phlegmonous, or laudable pus, is a fluid of the colour and consistence of cream, readily miscible with water, in which after a time it sinks; it does not admit of being drawn out into threads, and exhibits usually an alkaline, though sometimes an acid, reaction.

Like mucus, which it resembles so closely, pus is made up of two constituents, the one fluid, the other solid; these, if allowed to stand at rest for a time, will undergo a spontaneous separation from each other, the corpuscles subsiding to the bottom, and the fluid or serum floating upon the top; this also will be frequently observed to be covered with a delicate film composed of oil globules. The fluid portion of pus, as of mucus, is probably the only essential, as it certainly is its only distinctive constituent; but while the latter is sometimes free from globules, the former is never without a greater or less amount of corpuscles, on the presence and numbers of which its opacity, its colour, and its consistence mainly depend.

The general characters of pus, however, undergo many changes in disease; thus its consistence, colour, smell, and all other sensible qualities, vary greatly in pathological conditions.

IDENTITY OF THE PUS AND MUCOUS CORPUSCLE.

The globules of pus resemble in all essential particulars those of true mucus, the characters of which have been already described; thus, they present the same form, the same constitution, and they comport themselves in a manner almost identical with chemical reagents. (See Plate XI. fig. 1, and Plate XIII. fig. 1.)

In one respect only can a difference in the effect of reagents on the pus and mucous corpuscles be detected; this difference is, however, one of degree, and not of kind; thus, the mucous corpuscle is less readily acted upon by the acids than the pus globule; in the former, a solution of acetic acid, not too concentrated, will often disclose but a single, although large, nucleus ; while the same solution applied to the latter, will render apparent seldom less than three or four nucleoli. (See Plate XIII. fig. 2.) This is, however, by no means a constant result, and the effect of the application of strong acetic acid to the mucous globule is almost invariably to render apparent three or four


184 ORGANIZED FLUIDS.

nucleoli; so that, from the circumstance of the number ot nuclei disclosed by acetic acid, no opinion can be formed as to the nature of the corpuscle, whether it be a mucous or a pus corpuscle. Of the accuracy of this view, notwithstanding that a contrary opinion is held by many observers, not a doubt can be entertained.

It is not in every example of pus that we find the well-formed and spherical corpuscles, which characterize healthy and normal pus. In the pus which has been long secreted, as in that of old abscesses, we find but few corpuscles, the majority being broken up and reduced to their elementary particles. (See Plate XIII. fig. 5.)

The best examples of pus corpuscles are seen in pus which has been recently secreted, as in that just formed on some healthy granulating surface. (See Plate XIII. fig. 1.)

When, therefore, pus and mucous globules are spoken of, it is not to be understood that these terms indicate two distinct structures, but merely the occurrence of the same solid element in two fluids, which, although usually presenting some points of difference, are in all probability not essentially distinct.

THE NATURE, ORIGIN, AND FORMATION OF PUS CORPUSCLES.

In having indicated the nature of mucous globules, we have also, to a very great extent, pointed out that of pus corpuscles, seeing that the corpuscles of both have an organization precisely similar.

One of the earliest opinions formed in reference to the nature of pus was, that it was constituted of blood deprived of its colouring matter, a view which was entertained even before the discovery of the blood corpuscles themselves.

Subsequently to the period of the detection of the red corpuscles in the blood, many observers have conceived that pus consists of these corpuscles altered merely in colour.

A third opinion in reference to the formation of pus and mucous globules is that of Vogel, who maintained that they arose out of a transformation of the epithelium, the nuclei of which constituted the corpuscles. This view, although not without ingenuity, has but little even of probability to recommend it, and it will be perceived that it is the very reverse opinion to that which is maintained in these pages, and which is, that the epithelium is itself derived from mucous and pus globules.

We have already, under the head of Mucus, adverted to the opinion of Addison, that mucous and pus globules are altered colour


pus. 185

less blood corpuscles, an opinion which we have also endeavoured to refute, principally by reference to the impossibility, save from lesion, of the escape of the white corpuscles from their containing vessels.

Reference has also been made to the view entertained by Henle respecting the nature of pus corpuscles, who says of them that they are nothing else than elementary cells in process of being transformed into those of the tissue, which the organism regenerates in the injured part.

I also agree with Henle in considering pus corpuscles to be elementary cells, but I differ from him in not regarding them as representing the cells of the tissue in which the pus is formed.

Pus corpuscles I conceive to be identical with mucous corpuscles, and these again are to be regarded as repi'esenting an early stage in the development of epithelial scales.

Further, it is here supposed that the formation of pus is to be viewed in the light of a salutary process, and as indicating the effort on the part of the organism, where suppuration occurs as the result of lesion of any kind, to repair the mischief sustained, and which it does by the elaboration of pus corpuscles capable of being transformed into a protecting epithelium.

In support of this view, reference may be made to the fact that it is by no means uncommon to encounter epithelial scales mixed up with the ordinary pus corpuscles contained within the cavity of an abscess, or covering the surface of an old ulcer.

But, it may be asked, how happens it then that all pus corpuscles do not become converted into epithelial scales, and that so many of them are discharged or thrown off from the system without attaining to the higher degree of development of which they are stated to be susceptible ?

This arrest of development doubtless arises from the rapidity with which the pus corpuscles are formed, and which is indicative of the strength of the Vis medicatrix naturce, the result of which is that the earlier formed corpuscles become displaced by the more recently developed ones, and are thus removed without the sphere of growth, in consequence of which they perish.

Having thus considered the nature of pus corpuscles, we will next endeavour to form some opinion in reference to their origin and mode of formation; in these respects also an essential correspondence doubtless exists between pus and mucous globules.

Mandl attributes to the pus globule the same mode of formation


1S6 ORGANIZED FLUIDS.

which he has described as belonging to the white corpuscles of the blood, that is, that they are formed external to the vessels by the aggregation of molecules precipitated from the fibrin, and hence Mandl terms both the white and pus corpuscles "fibrinous globules."

This view of the formation of pus corpuscles is supported also by the observations of Vogel (already cited) made upon abraded surfaces.

Mandl, therefore, is most probably correct in his opinion as to the mode of formation of pus corpuscles, viz: by precipitation; but it is at the same time almost certain that they are not constituted of fibrin, as supposed by that micrographer : this may be inferred from the different manner in which acetic acid acts upon fibrin and pus corpuscles; thus, the former swells up, and is rendered soft and friable by its application, while the latter under its influence become smaller, and their contained molecules more distinct.

Donne dissents from Mandl's view altogether. At page 191 of the Cours de Microscopie, M. Donne expresses himself as follows: — "Thus I do not admit that the globules of pus are formed at the expense of the fibrin of the blood ; that they ought to be considered as a sort of precipitate of the fibrinous part of the fluid blood; and in spite of their analogy of structure and composition with the white globules of the blood, I nevertheless do not admit that they have any thing in common in their origin and in their intimate nature .with these last. I regard the globules of pus as a product of special secretion direct from the pus forming membrane."

There appears to me to be much of error in the preceding observations: there is doubtless very much in common between the white corpuscles of the blood and pus globules, viz: a common mode of formation and a common function to perform.

At the same time it must be admitted, with Donne, that the surface or membrane, from which the pus proceeds, is also intimately associated with the development of the pus corpuscles.

DISTINCTIVE CHARACTERS OF MUCUS AND PUS.

We have now to ask ourselves the question, which doubtless many have applied to themselves before, viz: what are the distinctive characters between mucus and pus revealed to us by the microscope, and the satisfactory recognition of which has been deemed to be of so much importance?

To this inquiry no sufficient answer has as yet been returned: this difficulty the microscope has failed to solve; and this, in all probability,


pus. 1S7

for the very adequate reason, that between the fluids in which a distinction has been sought, no microscopic difference exists. The inquiry has been made on the false assumption that mucus and pus are really essentially distinct ; and its importance has been magnified by the idea that it would impart, as indeed it undoubtedly would do, if real, increased assistance in the diagnosis of disease.

Since, however, the establishment of the fact that pus may be formed independently of any appreciable structural lesion, much of the interest which was supposed to attach to this inquiry has been lost, and that which still appertains to it has been further lessened by the demonstration at which we have arrived by means of the microscope, of the perfect identity of pus and mucous corpuscles.

Now, the manifestation of this identity by the microscope is not less a triumph of that instrument than if it had really proved that the notion of physiologists was actually founded on fact, and that there does really exist a tangible difference in the microscopic characters of the two fluids.

Notwithstanding the absence of any positive known microscopic character, whereby at all times, and in all conditions, pus may be discriminated from mucus, this want of knowledge, arising from the very sufficient fact to which allusion has already been made, viz: that no such character really exists, the two fluids under discussion may frequently be distinguished, at a glance, by certain outward and physical properties and appearances, and this is especially the case when they occur without admixture with each other.

These differences in the outward character of the two fluids are not always, however, equal to their discrimination, and which arises from the fact, that they are all of them subject to the greatest possible variation, so that there is not one which can be regarded as truly distinctive. Thus, in morbid conditions, the one fluid will pass by insensible degrees into the other, or they will both be mingled together in such proportions as to set at defiance all physical means employed to distinguish them.

But it may be said that the chemist can at all times distinguish pus from mucus: there can be no doubt but that, when all other means have failed, he can occasionally arrive at a tolerably accurate conclusion, but it is conceived that his powers in this respect are also limited.

Now, the physical and chemical difficulties encountered in the endeavour to discriminate pus from mucus arise in all probability,


188 ORGANIZED FLUIDS.

from the same cause which rendered it microscopically impossible so to do, viz : that no constant or essential difference does really belong to these fluids, whereby at all times they may be characterized.

Normal mucus and pus may be contrasted as follows : Mucus is a thick, tenacious, and transparent substance, easily admitting of being drawn out into threads, not readily miscible with water, in which it floats, not so much from its less specific gravity as from the circumstance of its great tenacity, allowing it to retain in its substance numerous air globules, which thus render it specifically lighter than the water: it exhibits sometimes an acid, and sometimes an alkaline reaction, according to the nature of the surface from which it proceeds ; and it contains imbedded in its substance solid particles of two forms, globules and scales: the former are present in alkaline mucus, the latter in that which manifests an acid reaction.

Pus, on the contrary, is a thick, opaque, somewhat oily substance, which does not admit of being drawn out into threads, is readily miscible with water, in which it sinks ; its chemical reaction varies, being sometimes alkaline, at others acid : the solid particles which it contains are mostly of one kind, globules : these are always very abundant, and float freely in the fluid portion of the pus, while in that of mucus they are unable to do so on account of its tenacity.

Healthy mucus and pus, when thus contrasted, may frequently be distinguished from each other, but it is in unhealthy conditions of these two fluids, and especially when they occur mixed together in variable proportions, that the difficulty of discrimination is felt, and that the want of a certain and positive character, whereby the diagnosis may be always established, is experienced.

This mixture of mucus and pus may actually exist, or it may not, in cases of suspected phthisis, in which sputa are present. Now, it is in cases of this description that we recognise the importance of the discrimination of these substances, and it is precisely in these and similar instances that the microscope utterly fails us, for the want of an ascertained and tangible difference in the two fluids submitted to the test of its powers.

Even the most marked physical qualities of pus, such as its opacity and tenuity, may all be effaced by the employment of certain reagents, and converted into those which are characteristic of mucus; thus, pus, by the addition to it of liquor potasses or of ammonia, is rendered transparent, and is transformed into a thick and tenacious substance, resembling mucus closely. This singular fact has been noticed by


pus. 189

both Addison and Donne, and on it the former clever observer has built a theory remarkable for its ingenuity, but which is here, nevertheless, deemed to be incorrect.

The change of pus, from an opaque substance to a transparent one, doubtless results from the solution of the pus corpuscles, and to the presence of which the colour and opacity of pus is due ; of the increased density and tenacity of the pus thus treated, it is less easy to afford a satisfactory explanation.

Addison thus accounts for it: The mucus and pus globules, he says, contain filaments imbedded in a fluid; these. the liquor potasses sets free by dissolving the envelopes of the corpuscles, and it is upon these filaments that the tenacity of mucus, and of pus so acted upon, depends. Mr. Addison, however, carries his reasoning upon the fact of the conversion of pus into a fibrillating substance similar to mucus still further. The white corpuscles of the blood, he states, also contain fibres, and that these corpuscles, immediately on their abstraction from the system, burst, giving issue to the contained filaments.

These filaments he conceives to constitute the fibrin of the blood, which he declares does not exist in that fluid as fibrin, but is only liberated from the corpuscles after the abstraction of the blood from the system.

The entire of this theory is here conceived to be erroneous, and this for the following reasons :

1. The existence of such filaments in the white corpuscles has not been proved.

2. The bursting of these corpuscles, referred to by Mr. Addison, is an occurrence which is rarely, if ever, seen to take place while they remain imbedded in the liquor sanguinis.

3. The actual consolidation of the fluid fibrin may be witnessed to occur on the field by the microscope in a drop of blood, and wholly independent of any rupture of the white corpuscles, which remain without appreciable alteration.

There is some consolation, however, in knowing that this inquiry is not of so much importance as it would appear; for even were we able to make the distinction which has been the subject of so many anxious thoughts, and decide that pus did exist in the sputa, yet this fact, viewed separately, would not prove that disease of the lungs did really exist, since it is ascertained that pus may be formed without any structural lesion; and, further, if lesion were really present, it would not necessarily follow that this had its seat in the cells of the


190 ORGANIZED FLUIDS.

lungs, for it might be situated either in the bronchi or larynx. Thus, even in this supposed case, the diagnosis would be subject to considerable uncertainty.

Various opinions have been expressed by different observers in favour of the possibility of distinguishing pus from mucus. To some of these we will now refer.

There is always met with in pus, in greater or less quantity, globules of oil; the presence of these was conceived by Gueterboch to afford a sign, absolutely distinctive, between pus and mucus ; that they are not so, however, is proved by the fact that similar globules are occasionally encountered in normal mucus.

Weber conceived the idea that the fluids might be distinguished by the size of the globules contained in them, the pus globule being twice as large as that of mucus : this character is likewise too uncertain, and too variable for the purposes of discrimination.

Lastly, Gruithuisen indicated, in solutions of pus and mucus in water, certain animalculae; those generated in the former being different from those formed in the latter solution. By means of these he asserted that pus might always be known from mucus; but the infusoria described by him are not confined to the fluids in question, but are such as are formed almost indifferently in any solution of animal matter. It would appear, then, that up to the present time no satisfactory and direct means of distinguishing pus from mucus have been detected, and this for the reason assigned, that the two fluids are essentially identical.

DISTINCTIONS BETWEEN CERTAIN FORMS OF MUCUS AND PUS.

Although it is impossible to discriminate between true mucus and pus by means of the microscope in a positive manner, we are yet enabled to distinguish with that instrument false mucus from pus, because in this mucus the corpuscles exist in their fully developed form of tesselate epithelium. Now, this power of discrimination is not without importance, as will be perceived immediately.

Many persons on arising in the morning are in the habit of expectorating more or less of a substance bearing much resemblance to pus. This habitual occurrence is not unfrequently a source of much uneasiness, not merely to the person the subject of it, but also to his medical adviser whom he is led to consult upon it.

Now, in such cases as these, it is often in our power to dispel the anxiety of our patient and our own at the same time ; for the solid


pus. 191

constituents of such sputa are frequently found to consist almost entirely of epithelial cells, in which case we may safely pronounce that they are not purulent; if, on the contrary, the sputa contain only globules, the evidence which this fact would furnish, although apparently, and indeed most probably, unfavourable, would still be but of a doubtful nature.

Again, the microscope will frequently determine the nature of a suspected fluid, by indicating in it the existence of shreds of cellular tissue, muscular fibrillae, and a variety of other organisms which enter into the formation of the human body; and by the presence of one or more of which, not merely the nature of the puriform matter may be ascertained, but also the locality from which the pus had itself proceeded.

DETECTION OF PUS IN THE BLOOD.

From what has been said in reference to the structural identity ot the white corpuscle of the blood with that of mucus and pus, we are prepared for the announcement that no known characters exist whereby the presence of pus in the blood may be established by the microscopic examination of that fluid.

That the elements of pus in some cases are really present in the blood, circulating with it, scarcely admits of a single doubt, since it is not unfrequently met with in situations, such as on the lining membranes of the vessels, where it is utterly impossible for it to remain without some portion of it becoming commingled with the blood.

The same fact is also proved by the spontaneous absorption ot large collections of matter, an occurrence which is not unfrequently witnessed, and which is only to be accounted for on the assumption that the elements of pus are again absorbed into the blood from which originally they were derived.

There can scarcely be a question, then, that pus is occasionally contained in the living blood, although we possess only indirect means of establishing this fact ; and according to the views here entertained, it may be present in the blood in two ways: thus, as we have seen, it may be formed in the blood-vessels themselves, or it may be formed without those vessels, and again reabsorbed into the blood from which in every case it almost immediately proceeds.

But pus, as we know, is composed of two elements, the one fluid, the other solid, the globules. Now, we must not expect to see pus circulating in the blood as pus, although that liquid may contain all


192 ORGANIZED FLUIDS.

the elements of pus: the fluid portion of course, as soon as it enters the circulation, is dissipated, the solid alone remaining, and this does not constitute pus, but is only one element in the constitution of that fluid.

In certain states of disease, the presence in the vessels of an unusual number of white corpuscles has been observed; now it is but little probable, that these are derived from the reabsorption of pus, which had been previously formed without those vessels ; it is more natural, and more consonant with known facts, to suppose, that this accumulation is to be regarded as an indication that the disposition to the formation of pus, on the part of the blood and of the system, exists to an unusual extent, and that such a condition of the vital fluid always precedes sudden and extensive purulent collections.

Except in the case of the formation of pus in the blood-vessels themselves, it is scarcely possible to suppose that the pus corpuscles are taken bodily into the circulation again; but it would rather appear, from the condition of pus in most abscesses, that the corpuscles become disintegrated and reduced to their elementary particles, and that thus they enter the circulation again in a fluid state.

The artificial admixture of pus with the blood immediately after its escape from a vein, and before its coagulation has commenced, is productive of somewhat singular results. The clot formed in blood, which has been mixed with one quarter part of its own quantity of pus, is soft, diffluent, and dark coloured, sometimes almost livid, and the red corpuscles are found to be wrinkled and deformed, part of their colouring matter having escaped from them and passed into the serum.

These changes ensue in from twenty-four to forty-eight hours, and possibly result from the state of decomposition in which the pus itself might have been when introduced into the blood, and which condition it communicated to the mass of the blood itself.


There are many substances and fluids having resemblance to pus which are not really purulent; thus, softened clots of fibrin, which are so frequently encountered, especially in phlebitis, bear the closest possible similitude to true pus in general appearance, and yet in their intimate structure they are totally dissimilar, as may be clearly determined by means of the microscope.

If a portion of softened fibrin be examined microscopically, it will


pus. 193

be found to be made up of a granular material, from which pus corpuscles, or corpuscles similar to them, are either entirely absent, or in which they occur but in very small numbers. Now, with true pus, the reverse is the case; the corpuscles are its chief and most conspicuous element.

It is only by means of the microscope that the nature of softened fibrin can be ascertained; until within the last few years it has always been mistaken for true pus, and the occurrence of masses of fibrin thus altered in the blood-vessels has led to the opinion that the formation of pus in them is not an unfrequent event.

On the other hand, fluids are sometimes met with which look very unlike proper pus, and which are yet found on examination to be veritable pus. These facts show the necessity of a careful microscopic examination in all important and doubtful cases.

METASTATIC ABSCESSES.

Another notion, the erroneousness of which has been rendered manifest by means of the microscope, is that which has been entertained in reference to the removal of an abscess seated in one part of the body, and its subsequent deposition in another situation.

The knowledge of the existence of pus corpuscles in the fluid of abscesses, and the fact that no channels exist by which they can be conveyed bodily from one part of the system to another, clearly show that any such translation of the matter of an abscess as that presumed is an occurrence beyond the range of possibility.

Abscesses may indeed be reabsorbed into the system, as daily observation teaches us to be the case, and other purulent depositions take place subsequently to the resorption of the matter of the first abscess ; but the elements of pus, and assuredly its solid constituents, are not carried into the constitution bodily and without alteration; the corpuscles doubtless become disaggregated, and in all probability reduced to a fluid state previous to absorption, so that it cannot be the same purulent matter which constitutes the pus of supposed metastatic abscess.

The simultaneous or consecutive occurrence of abscesses in different parts of the body, may be satisfactorily explained by reference to the condition of the system, or perhaps more immediately of the blood itself, which is evidently charged with purulent matter, and of which it. relieves itself by the formation of abscesses.

13


194 ORGANIZED FLUIDS.

VENEREAL VIBRIOS.

M. Donne has discovered in- the pus of syphilitic primitive ulcerations, and of chancres which have not been treated with topical applications, numerous vibrios of excessive tenuity. (See Plate

XIII. fig. 6.)

These vibrios are not encountered in the pus of secondary chancres, nor even in that of buboes, which, according to the experiments of M. Ricord, is capable of giving origin to a chancre by inoculation.

Neither are they to be met with in the pus proceeding from wounds, nor in fetid pus altered by the contact of the air.

Again, in the instances in which suppuration has been artificially excited around the edge of the glans penis, the ordinary situation of primary syphilitic ulcerations, the vibrios are invariably found to be wanting in the discharge thus created. This experiment proves that locality has nothing to do with the development of the vibrios.

Finally, if inoculation be practised with the pus of a chancre containing the vibrios, the matter of the pustule resulting from the inoculation will also be found to contain the animalcules.

Now, the inference to be deduced from these several facts and experiments is, that if the vibrios in question be not intimately connected with the propagation of the syphilitic virus, that the matter of syphilis is at least peculiarly fitted for their development.

It is probable that the presence of these vibrios accounts, in a great measure, for the beneficial effects of topical applications, which act by killing the animalcules.


Article V. — Milk

The general aspect and qualities of milk are known to all; they need not therefore be here detailed.

Healthy and fresh milk, when submitted to the action of test paper, exhibits an alkaline reaction: in states of disease, however, and some time after its removal from the mammary gland, it frequently manifests more or less of an acid reaction.

Like the other fluids which have as yet been described in this work, milk is made up of two distinct elements, the one fluid, the serum — the other solid, the globules; these, a few hours after its abstraction from the system, and when left at rest, undergo to a certain extent a spontaneous separation from each other, the larger globules, ascending to the surface, forming a scum or cream, while the smaller remain diffused through the subjacent serum.

The following analyses will serve to give an idea of the composition of milk.

The relative proportions of the organic constituents of human milk are thus estimated by Simon : 88 • 06 water. 3 ' 70 caseine. 4 "54 sugar. 3 • 40 butter.

0*30 salts, extractives, &c. The inorganic components of the milk of the cow are computed as follows by Haidlen :

Chloride of sodium - - ■ 024.

Chloride of potassium - -0144.

Soda - - - -0-042.

Phosphate of lime - - 0'231.

Phosphate of magnesia - - ■ 042.

Phosphate of the peroxide of iron - 0*007. From the above brief sketch of the constitution of the milk, it will be seen that a very close analogy exists between that fluid and the blood : like it, the milk is made up of two parts — the one solid, the other liquid ; like it, too, it contains all the elements requisite for nourishment and development, it serving for both during a very long period of the life of the human species.


196 ORGANIZED FLUIDS.


THE SERUM OF THE MILK.


The separation of the serum and the globules, accomplished in an imperfect manner naturally, is more completely effected artificially by filtration; the serum, by means of the ordinary filtering paper, may be obtained transparent and colourless, almost free from globules, these being for the most part retained upon the filter.

It may, however, be observed, that the first portions of serum which pass through the paper will be more or less coloured in consequence of their containing a certain number of the smaller globules, which had escaped through the interstices of the paper; these coloured and semi-opaque portions of serum should be rejected.

The serum contains dissolved in it the sugar, and the principal portion of the cheese of milk, as well as certain salts, the principal of which are pointed out in the analysis of Haidlen.

The cheese or caseine is an animal principle, which in its properties approaches closely fibrin: it is precipitated by the mineral, the acetic, and the lactic acids.

Although the greater portion of the caseine exists in the milk in a fluid condition, M. Quevenne appears to have established the fact, that it is also present in a solid state in the form of globules, these being exceedingly small, and refracting but slightly the light; the same globules may also be detected in recently precipitated cheese. (See Plate XV. fig. 5.)

M. Donne has shown that these cheese globules may be demonstrated by the process of filtration; thus, the first few drops of the milk of the cow, the ass, or the goat, which pass through the filter, and which are generally white and opaque, being rejected, and the second portion of filtered milk being preserved, and allowed to remain undisturbed for a few minutes, it will be seen to separate into two parts, the inferior of which is clear and transparent, while the superior is somewhat opaque. Now, if a drop of the fluid of this inferior layer be examined with the microscope, it will be found to contain an innumerable quantity of globules of exceeding minuteness, and refracting the light but feebly, as well as occasionally other globules more rare, larger, and refracting the light very strongly; the former are the cheese globules, and the latter the proper milk globules.


MILK. 197


THE GLOBULES.


It is to the presence of the globles which occur in such vast quantities in each drop of healthy milk that the colour and opacity of that fluid is due.*'

These globules are of perfect rotundity, their surface being smooth, presenting a pearly aspect, and refracting the light strongly; the circumference of each globule is dark and the centre light : the globules vary greatly in size; the smallest, which are in active molecular movement, being reduced to mere points, and not exceeding the t 8-7oo of an inch, the largest frequently attaining the 20V0 of an inch, and the medium size ranging between the 4 oV of an inch in diameter and the 45V o- (See Plate XIV. fig. 1.) In milk which is healthy, the globules float freely in the serum, and do not adhere to each other.

Such is the form, appearance, and variety of size exhibited by the milk globule; much difference of opinion has existed in reference to its organization, some observers conceding to it a very complex structure, others denying it even the most simple organization.

Some of the more remarkable of the opinions entertained by the more noted investigators may here be referred to.

According to Turpin, "the structure of the milk globule consists of two spherical vesicles, fitting the one into the other, and enclosing in their interior very fine globules and buttery oil."f

Mandl says, " the globules of milk ought then to be considered as organized corpuscles, composed of a membrane probably formed of cheese, and of contents which constitute the butter." J

Henle writes, the globules of milk "are not simple molecules of grease, and have an independent membrane surrounding them ;"§ this he elsewhere states to be probably composed of caseine, in which respect there is an agreement of opinion between Henle and Mandl.

The complex structure ascribed to the milk globule by Turpin it is altogether impossible to demonstrate ; and the experiments and observations which have hitherto been made in reference to its constitution

  • Leeuwenhoek first clearly indicated the existence of these globules in the milk

in the following terms: " Vidi multos globulos, similes sextas parti globuli sanguinei; et etiam alios, quorum bini terni aut quaterni se invicem modo attingebant, fundum versus descendere; et multos varies magnitudinis globulos in superficie fluitantes, inter quos posteriores adipem sive butyrum esse judicabam."

f Annates des Sciences Naturelles. j Anat. Micros, p. 53.

§ Anat. Gen. t. vii. p. 522.


198 ORGANIZED FLUIDS.

are entirely opposed to his view, which may safely, therefore, be considered to be incorrect.

Mandl founded his belief of the existence of a distinct membrane enveloping the globules mainly on the following observation: He remarked that if a little drop of milk be compressed strongly between two plates of glass, the upper plate at the same time being drawn over the surface of the other in a straight line, the milk globules will be broken up by the compression, and drawn out into a certain form : if a magnifying-glass be applied to the globules thus compressed, they will be seen to present the appearance of long pale and straight lines, with smaller straight lines placed usually at right angles to the larger ones. "These little lines," he says, "are nothing else than the curled membranes of the globules, the contents of which, the butter, constituting the long streaks : we may easily convince ourselves of this by adding a little water. The streaks disappear, and we see in their place oleaginous drops of different forms, while the little membranes remain either attached to the glass or indifferently curved, swimming in the serum. These membranes are insoluble in ether, which dissolves the drops."

These observations of Mandl, presuming for a moment that they are accurate in every particular, are yet insufficient to prove the existence of a distinct membrane surrounding the globules, although they certainly would be so, if correct, to establish the fact that they are constituted of two different substances, the one of which is soluble in ether and the other insoluble. Had iodine been employed, and had it been imbibed by the supposed membrane, and turned of a deep brown, the reality of the existence of the membrane in question might have been considered as demonstrated : but we know that iodine does not affect the colour of the milk globule in the least.

I am far, however, from attaching the smallest importance to the experiment of Mandl, because I conceive that he has misinterpreted the appearances which he noticed. The larger streaks are not constituted of a single elongated globule, but are made up by the union of several milk globules, as is evident — first, from the size of the streaks, and, second, from the traces which they bear of such a composition in themselves; as, for example, the occurrence of contractions at certain intervals, while the smaller lines, and which are most generally absent, are formed usually by other globules of less size joining at an angle the larger streaks. The solubility of the one in ether and the insolubility of the other in that reagent, I have not been able to observe.


MILK. 199

The opinion of Henle, that the milk globule is furnished with an envelope, rests chiefly upon the manner in which acetic acid acts upon it.

Henle thus describes the effects of the application of acetic acid:

" Treated by dilute acetic acid, the globules of milk undergo, little by little, a remarkable change; some of them become oval or take the the form of a biscuit; upon others, appear gradually on one or many points a smaller globule, which rests upon the margin, and increases in an insensible manner." *•■*.*« If more acetic acid be added, the milk globules appear, as it were, melted down with smooth but irregular borders : they approach the one to the other, and unite into large masses, which resemble perfectly melted fat which has run along in an irregular manner. When to a drop of milk are added two drops of concentrated acetic acid, and the mixture then placed under the microscope, we no longer perceive any regular globule of milk, or, at least, we discover but very few: the most are reduced into one or several irregular particles, which, with the naked eye, may be distinguished upon the surface of the drop, which otherwise has become clear. The same changes are produced in the space of a few days, when the milk, abandoned to itself, becomes acid by the metamorphosis of its sugar."*

These ingenious observations of Henle, like those of Mandl, are yet insufficient to demonstrate the existence of a distinct and organized membrane surrounding the milk globule, although they would be assuredly so, if correct, to render it quite certain that it is enveloped with a coating of a material very distinct from fat, and probably of the nature suggested by Mandl and Henle

Here, again, however, it becomes a question whether the appearances noticed by Henle have not been misinterpreted, and whether the internal buttery substance does really protrude through apertures in the envelope of the globule occasioned by the action of acetic acid: in the first place, it seems to me that the milk globules are too small to allow of the determination of the point in question with any degree of certainty ; and, secondly, that in those instances in which observers might fancy that an escape of the included substance of the globule through its envelope had really occurred, such an appearance is, in all probability, due to the adhesion together and partial fusion of two or more globules. (See Plate XV. fig. 4.)

  • Henle, Anat. Gen. p. 521, 522.


200


ORGANIZED FLUIDS


There are other observers again — as Wagner, Nasse, arid QueVenne — who would deny to the milk globule all organization, and who regard it as of a perfectly homogeneous nature.

The truth in this instance, as in so many others, would appear to lie in the mean. That the milk globule is not provided with a distinct and separate membrane, similar to that of the mucous corpuscle, is proved by the impossibility of demonstrating the existence of any such structure, as well as by the absence of a double line around its margin, the non-effect of iodine, and the coalition of the globules resulting from pressure, first observed by Dujardin.

That it is not constituted of a single perfectly homogeneous substance, is also demonstrated by the observations of Mandl and Henle, and especially by those of the latter observer on the effects produced by acetic acid.

That the milk globule is not wholly composed of fatty matter, is shown by its insolubility in boiling water raised to a very high temperature, in boiling alcohol, in the alkalies, and by the effects of the application of acetic acid. Ether dissolves the milk globules : their solution, however, it does not entirely accomplish on its first application, although the ether, the moment it comes in contact with the globules, causes them to lose their rotundity, to fall down, and to run together into masses of various sizes, but most of which still present a circular outline.

If a drop of milk be examined microscopically, after its treatment by ether, a hasty observer might conclude, from noticing so many of the circular masses alluded to, that the reagent had not exerted any influence on the milk globules, and that these masses were the unaltered globules. This view, however, a little reflection would soon show to be incorrect; for many of the circular bodies now noticed on the field of the microscope are larger than even the largest milk globules, and all of them are flat and semi-fluid. (See Plate XV. fig. 3.)

The several facts now adduced, while they prove that the milk globule is not organized in accordance with the interpretation of the .word organization usually given, yet seem sufficient to establish the fact that it is composed of two distinct organic products — the one internal and fatty, and the other external, and possessed of properties distinct from fat.

This explanation of the constitution of the milk globule serves to explain also satisfactorily the facts above alluded to, viz: the non


MILK. 201

action of boiling water, alcohol, and alkalies, all of which affect more or less fat, as also the slower operation of the ether: it also shows why boiling alcohol should immediately dissolve the milk globules, to which a little acetic acid had been previously added, this latter reagent first removing their outer coating, which is insoluble in alcohol.

Between the globules of the previously-described fluids — those of the lymph and chyle, of the blood, mucus and pus, and globules of milk — no structural or functional relation whatever exists ; the former being complex and definite organizations or cells, and the latter constituted of two distinct substances indeed, yet want entirely the attributes of cells, being destitute of nucleus and cell wall.

It is of the globules just described that the cream is constituted, their accumulation on the surface of the milk being due to their lighter specific gravity; it is also by their incorporation with each other, and which is effected by the operation of churning, that butter is formed.

COLOSTRUM.

The milk which is secreted the first few days after child-birth has been denominated colostrum : it differs very considerably from ordinary milk, being of a yellow colour, of a viscous consistence, and containing a very large proportion of milk globules, which give rise to the formation upon it of a thick layer of cream; when treated with ammonia, it becomes glairy and tenacious.

Corresponding with the outward characters of the colostrum, there are others indicated by the microscope not less remarkable : thus, the larger true milk globules which occur in it are but ill-defined, being irregular in form and size, appearing as though they were but imperfectly elaborated, and presenting rather the aspect of oil globules, while the smaller ones are like a fine powder strewn through the serum, and adhering to the surface of the larger globules, which also, in place of floating freely and separately in the serum, are agglomerated together as if held in union by some viscous material. (See Plate XIV. figs. 4 and 5.)

But besides the state of the ordinary milk globules just described, there are found in the colostrum peculiar corpuscles of a totally distinct structure : these were first discovered and described by M. Donne, who has denominated them " Corps granuleux."

These corpuscles are mostly several times larger than the milk globules, are less regular in form, although usually more or less


202 ORGANIZED FLUIDS.

spherical in outline, and present a uniformly molecular aspect and a yellow coloration; the edges of the corpuscles sometimes appear smooth, as if possessed of an envelope ; at others, their margins are rough, and convey the impression that they are destitute of any external covering. See Plate XIV. figs. 3 and 4.) Occasionally one or more milk or oil globules are imprisoned in the substance of the corpuscles, which then occupy the position, although they do not discharge the office, of a nucleus.

Some difference of opinion is entertained respecting their intimate structure: Gueterboch, and probably Donne,* conceive that they are furnished with an investing membrane, and therefore that they are veritable cells, while Henlef regards them as masses or aggregations of granules agglomerated together in an amorphous and mucoid substance ; an opinion in which I concur.

Donne states that the colostrum corpuscles are soluble in ether, and therefore that they are of a fatty nature : the fact of their solubility, however, seems to me to be difficult to verify ; and from observations which I have made, I cannot help thinking that this point is scarcely as yet established. Certain it is that corpuscles larger than mucous globules, and in every way similar to the colostrum corpuscles, save that traces of nuclei may be detected in them, appear in colostrum treated with ether.

The " Corps granuleux " are insoluble in the alkalies, J are coloured brown by iodine, and the substance which unites the granules is dissolved by acetic acid.§

The state of the milk just described does not continue without alteration, each condition which has been alluded to undergoing a daily modification : thus the milk globules from day to day acquire greater uniformity of size and shape, they no longer adhere together, but float freely and singly in the serum, which does not become viscid on the addition of ammonia, the smaller dust-like globules also altogether disappearing ; at the same time the number of the colostrum corpuscles diminishes until at length none exist. (See Plate XIV. fig. 1.)

These several changes are all accomplished in the course of a few days, so that by the end of the twenty-fourth day, the milk has usually entirely passed from the condition of colostrum, and presents only its ordinary characters. The colostrum, however, does not

  • Cours de Microscopie, p. 401. f Anal. Gen. t. vii. p. 525.

J Donne, loc. cit. p. 401. JHenle, loc. cit. t. vii. p. 525.


MILK. 203

always pass through its various modifications in the time specified ; it may do so in either a shorter or a longer period than that stated: thus, the existence of the milk in the form of colostrum can scarcely be regarded as affording any very certain test whereby the age of the milk may be determined.

The colostrum corpuscles would appear to be almost peculiar to the human subject, for while their presence in the milk of woman is almost constant, their occurrence in that of animals — as the cow, the ass, and the goat — i%rare and exceptional.

Professor Nasse states that they disappear sooner in women who have borne many children than in those who have had but a single child.

Mucous corpuscles are also occasionally encountered in the colostrum. They are, however, neither very generally present, nor do they occur in any very great numbers.

The colostrum, or first milk, is possessed of purgative qualities.

PATHOLOGICAL ALTERATIONS OF THE MILK.

Persistence of this Fluid in the condition of Colostrum.

It has been stated, that usually by the end of the twenty-fourth day after child-birth, and frequently at a much earlier period, the colostrum has lost all its distinctive characters, and the milk has arrived at its perfect condition.

This transformation of the colostrum into fully- elaborated milk, it has been observed, is not always effected in the time named : it may be accomplished in either a shorter or a longer period ; thus, the milk in some cases loses the chief characters of colostrum in as short a space of time as three or four days, while in others it retains them for months after the birth of the child, and even until the end of lactation.

This persistence of the milk in the state of colostrum may be present without any suspicion of its existence being entertained, the milk exhibiting its ordinary outward appearances.

It is, therefore, only by means of the microscope that its true condition can be ascertained. Examined with this instrument, the characteristics of colostrum will be detected ; thus, the globules which do not float freely in the serum, and which are large and ill-formed, will be seen to adhere together in groups, as though held in union by some viscous substance, and intermixed with them will be noticed numerous colostrum corpuscles.

It cannot be doubted but that such persistence of the milk in the form vi colostrum exerts a most injurious effect upon the child : the


204 ORGANIZED FLUIDS.

colostrum is, as we know, possessed of purgative properties; these, during the first days of the life of the infant, are necessary; their continuance cannot but impair its strength and health.

Recurrence of Colostrum.

M. Donne has established the interesting fact that milk which has entirely lost the character of colostrum, and which has reached its perfect maturity, may again pass into the state^of colostrum at any period during the course of lactation.

Thus, the milk which had at one time presented the constitution of perfectly formed milk has been seen by M. Donne to acquire gradually that which is indicative of the colostrum, it becoming viscous, and the globules contained in it, instead of floating freely and singly in the serum, uniting with each other, forming irregular masses, the granular and mucous corpuscles at the same time being present in it in considerable quantities.

In the instances in which the recurrence has been observed, engorgement of one or both of the mamary glands has usually preceded it.

When but one gland is affected, the milk of that gland only presents the characters of colostrum, that of the opposite side retaining its usual properties and constitution.

The recurrence of the colostrum would appear to depend, as a cause, either upon lesion of the mammary gland, or upon a deranged or vitiated condition of the health.

Influence of prolonged Retention of the Milk on its Constitution.

M. Peligot has made the observation, important in a practical point of view, that the milk which has been allowed to remain for a long time in the breast becomes thin and watery, an effect which is contrary to that which occurs in reference to most other secretions of the economy, the urine and the bile, the density of which is heightened by retention.

Thus, if the milk abstracted at one time, and which has been long secreted, be divided into three parts, each being received successively into a distinct vessel, the first milk will seem to be poor and watery, the second more rich, and the third the most so of the entire. The first portion is to be regarded as that which has been longest formed, and the third as the most recently secreted.


MILK. 205

The knowledge of the above fact leads to one practical result in the case in which the milk is too rich for the digestive powers of the child ; thus by allowing such milk to remain for a longer period than usual in the breast, a fluid of lighter quality and less abounding with nutritive principles will be obtained.

A second effect of prolonged retention or engorgement of the milk in the breast is to occasion the aggregation of the globules into masses. (See Plate XIV. fig. 6.)

Pus and Blood in the Milk.

Having now described those constituents by the combination of which milk is formed, as well as the several conditions in which these may be encountered, we may next refer to those structures which occasionally occur in milk as the result of disease.

Thus, the corpuscles of both pus and the blood are sometimes encountered in the milk, those of the former fluid occurring much more frequently than those of the latter.

The puriform matter which issues from the breast in cases of abscess of that gland is made up of a mixture of pus and milk globules, with occasionally blood discs. (See Plate XV. fig. 1.)

But both pus and blood corpuscles* the latter very rarely, may be contained in the milk which issues from the breast through its natural channels.

I was so fortunate as to meet with an excellent example of blood in the milk, the occurrence of which is so rare that Donne, at the period of the publication of the " Cours de Microscopie," and with all his researches on the milk, had never encountered a single instance of such pathological alteration in the human subject. The case in which this occurred was that of a young woman confined of her first child ; the milk not appearing at the usual time, the friends became anxious, and one of them, more officious and more ignorant than the rest, had the nipples drawn with such vigour and effect as to cause the extraction of a liquid half blood and half milk. (Plate XV. fig. 2.) The occurrence of blood corpuscles in the milk can only take place as the consequence of a rupture of some of the smaller blood vessels which are distributed through the mammary gland.

The above facts clearly show the impropriety of applying an infant to the breast in cases of inflammation and suppuration in that organ.

Not the least difficulty need be experienced in the detection of pus and blood corpuscles in the milk, their form and structure being so


206 ORGANIZED FLUIDS.

totally dissimilar to those of the proper milk globules. Reagents also affect the different kinds of corpuscles differently. Thus, the milk globules are soluble in ether, which does not materially affect the pus and blood corpuscles, the latter of which is dissolved by acetic acid, and the former only by the caustic alkalies.

The Milk of Syphilitic Women.

M. Donne has made repeated attempts to discover in the milk of women labouring under syphilis, in different forms, some element which would account for the transmission of the affection from the mother to the infant. These endeavours were, however, entirely fruitless ; nor is this result other than what might have been anticipated, for it is scarcely to be supposed that the venereal virus exists any where in a tangible form ; and if it really does so, it would still be a matter of impossibility to point out the channels by which any solid matter could make its way through the system and mingle with the secretion of the mammary gland.

The Milk of Women in the Case of the premature Return of their

Natural Epochs.

The milk of women in whom the natural periods have returned during the course of lactation, has likewise been carefully examined. Except in a single instance, however, it has not been found to present any thing remarkable in its characters. In the case referred to, it had degenerated to the condition of colostrum, and contained the granular colostrum corpuscles.

THE MILK OF UNMARRIED WOMEN.

The breasts of many women who have not been married are frequently found to contain an abundance of milk, and from those of most, more or less of a milky fluid can be obtained.

This milk exhibits all the characters of colostrum, containing even the peculiar corpuscles which distinguish that condition of the milk ; it is therefore, like the first milk, to be regarded as an imperfectly elaborated substance.

THE MILK OF WOMEN PREVIOUS TO CONFINEMENT.

The breasts of most women during the last few weeks of gestation contain more or less milk, which also presents all the characters of colostrum.


MILK. 207

The quantity of milk contained varies greatly; in some cases a few drops of a milk-like fluid only can be obtained ; in others it is more abundant ; and again, in other instances, it is still more plentiful, and rich in quality.

The question may be asked, does there exist any relation between the quantity and condition of the milk before confinement, and its state when it has arrived at perfection after this event has occurred ? In other terms, can one pronounce, by the milk in the breasts, beforehand, whether a woman will have a sufficient quantity of milk to nourish her infant ?

This question, which so often presents itself to the consideration of the medical practitioner, M. Donne has discussed at some length, and to it he replies thus :

" The secretion of the mammary gland," he says, " is after confinement in constant relation with the state which it presents during gestation, so that it is possible to know in advance, by the observation of its characters during the last months of pregnancy, what its condition will be when it shall have acquired all its activity after parturition."* This law, he states, is so general, that in the sixty observations which he has made on women of all ages and temperaments, he has met with but two or three exceptions.

Pregnant women Donne divides into three classes, founded upon the characters presented by the colostrum during the last months of gestation :

1st. Those in whom the secretion is small, and the viscous liquid contains scarcely any milk globules, mixed with a very few colostrum corpuscles.

2d. Those in whom the colostrum is more or less abundant, but poor in milk globules, which are small, ill-formed, and containing also colostrum and mucous corpuscles.

3d. Those in whom the colostrum is very abundant, rich in milk globules, which are of good size, and unmixed with any other corpuscles save those proper to the colostrum.

Now, the indications to be deduced from the different states of the colostrum just described are —

That the first state appertains to women in whom the secretion of milk after child-birth is either very little, or in whom there is produced but a serous milk, poor in nutritive elements, and therefore insufficient for the nourishment of the child.

  • Cours de Microscopk, p. 406.


208 ORGANIZED FLUIDS.

That the second condition indicates those in whom tne secretion of milk after confinement is either small or abundant in quantity, but which is always poor and serous.

That the third state of the colostrum belongs only to such women as have an abundant supply of milk of good quality.

THE MILK OF WOMEN WHO HAVE BEEN DELIVERED, BUT WHO HAVE NOT NURSED

THEIR OFFSPRING.

The mammary gland of women who have borne children, but who have not nursed them, is frequently found to contain milk many months after confinement.

This milk always presents the characters of colostrum.

MILK IN THE BREASTS OF CHILDREN.

A milk-like fluid can frequently be expressed from the breasts of infants and young children, both male and female.

This fluid, examined microscopically, has been found to exhibit all the characters of ordinary milk; and, in some cases, the colostrum corpuscles have even been detected in it.

DIFFERENT KINDS OF MILK.

The milk of one mammiferous animal resembles so closely that of another that it is often a matter of impossibility to distinguish, either with the naked eye or by means of the microscope, the different kinds of milk.

The milk of the ass may, however, be generally known by its watery aspect, its bluish tint, and its lightness; that of woman by the promptitude with which the layer of cream is formed upon it; but it is, above all, by the taste that the several kinds of milk are characterized : thus, the taste of the milk of the cow can scarcely be confounded with that of the ass or goat, nor can the flavour of the milk of woman be mistaken for that of any of these.

The microscope aids but little in the discrimination of the different kinds of milk: the globules of the milk of the goat are certainly smaller than those of the other species named, and those of the ass are less numerous; nevertheless, these characters are so little constant that they are not, in many instances, sufficient to distinguish them from the milk of the cow or of woman.

The number of globules contained in the milk of different animals doubtless varies considerably; but there is as much variation in this


MILK


209


respect as in those just referred to; and, therefore, this difference is not sufficient to distinguish the several kinds of milk.

RELATIVE PROPORTIONS OF THE ELEMENTS OF MILK.

Chemical analysis indicates a very great variety in the relative proportions of the different nutritive ingredients of milk; and this, not merely with respect to the milk of different animals,, but also in reference to that of the same species, and even of the same individual, at different times.

The truth of these remarks will be evident from an examination of the following analyses :

Analysis of the Milk of Woman, by Peyen. Butter, - - - - 5-16

Sugar and cream, - - - 7 ' 80


Analysis of the same, by F. Simon. Water, ....

Caseine, ....

Sugar, ....

Butter, — Salts, extractive matter, &c,


88


06


3


•70


4


54


3


40



30


100


00


Analysis of the Milk of Woman, the Cow, the Goat, and the Ass, by Meggenhofen, Van-Stiptrian, Liuscius, and Bonpt, and Peligot.*



Woman.


Cow.


Goat.


Ass.


Butter,


8-97


2-68


456


1-29


Sugar,


120


5 68


9 12


6-29


Caseine,


1-93


895


4-38


1-95


Water,


87-90


84'69


81-94


90-95


It will be seen from the above analyses that the milk of woman is the richest in butter, while that of the ass contains the smallest amount of that element.

The assertion made by Donn&, that the quantity of butter in the milk of the same species stands in relation with that of the other essential ingredients of the milk, although supported by the researches of Peyen and Peligot, is contradicted by those of F. Simon. Accord

  • This analysis is copied from the Cours de Microscopie of Donne.

14


210 ORGANIZED FLUIDS.

ing to the analyses of Simon, the quantity of sugar is greatest immediately after delivery; a few days being passed, this diminishes, and the amount of caseine, which was at first very small, undergoes a gradual augmentation. The butter Simon considers to be the most variable element of the milk, its variations not being reducible to any law.

The relative proportion of the different ingredients of the milk of animals may be modified, and almost altered, at will, by the adoption of a certain regimen.

GOOD MTT.V.

The purity and the richness of milk were formerly estimated by its specific gravity, which is about 1 '032; if the milk was poor in cream, or if it was diluted with water, it was supposed that the gravity of the fluid would be in the first case increased, and in the second lessened.

The cream being the lightest element of the milk, its deficiency or its abstraction would, of course, increase the density of the remaining fluid, and the addition of water, after the removal of the cream, which is also of less weight than milk which is even pure and rich, would, of course, raise the gravity of the milk either up to or even beyond its natural weight.

Now, the abstraction of the globular element of the milk and the addition of water are the two frauds most frequently had recourse to; and they are of such a nature as to elude detection by reference to the specific gravity of the milk, when they are both put in practice in combination.

The specific gravity test of the purity and richness of milk is, then, one which is fallacious, and therefore but of very little value.

It has been proposed by M. Quevenne, not merely to estimate the specific gravity of milk, but also to measure the layer of cream which forms upon it by repose. This ingenious method is scarcely more to be depended upon than the preceding, and is put at fault by the fact that the addition of water favours the ascension of the cream.

Thus, the layer of cream formed on milk to which water has been added will be thicker than that of unadulterated milk, this effect being the consequence of the lessened specific gravity resulting from the addition of the water.

Donne has made the statement, which is borne out by the analyses of MM. Peyen and Peligot, that the globular or buttery element of the milk stands in relation, in the milk of the same species of animal,


MILK. 211

though not in different species, with the other nutritive ingredients of milk, the cheese and the sugar. The analyses referred to are the following :

Milk of Woman, analyzed by M. Peyen. Butter, - - 5-16 5-18 5 20 Sugar and cheese, 7 • 80 8*10 9 ■ 80

Milk of Asses, analyzed by M. Peligot. Butter, - - 1-55 1-40 1'23 1'75 1-51 Sugar and cheese, 10 '11 7 '97 7 34 8"25 7 -80

Donne, therefore, proposes to estimate the purity and the richness of milk by means of the globular element contained within it. The eye alone will, in some measure, indicate the number of globules contained in the milk; for, since the opacity of milk is due to the presence of the globules, it may be concluded that the milk which is white and opaque is rich in globules, while that which is watery and transparent is poor in the same.

The microscope, however, is a more certain means of determining the number of the globules, although by means of this instrument we can only arrive at an approximative knowledge of their amount.

In order to estimate as nearly as possible the number of globules existing in the milk, M. Donne has invented an apparatus which he has termed a lactoscope. By means of this instrument, the milk can be examined in very thin layers ; and in proportion to the opacity of the milk spread out in such layers, so will be its richness — the deeper the stratum, the richer the milk.

There is one fallacy attending the use of this instrument which requires to be noticed; this, however, is one which has reference to its employment in testing the quality of the milk of the cow, the ass, and the goat, and not of the milk of woman.

The milk of commerce is frequently adulterated with substances, such as chalk and flour, which are intended to heighten its colour and opacity ; the presence of these then in the milk would, to a certain extent, lessen the value of the opinion to be deduced from an examination of the milk with the lactoscope of Donne.

The effect, however, of the admixture of chalk and flour, in heightening the opacity of milk, is not so considerable as might be supposed, and this is especially found to be the case when it is spread out in thin


212 ORGANIZED FLUIDS.

layers, as in the lactoscope. Moreover, the presence of an insoluble substance in the milk might be detected by means of the microscope.

Applied to the examination of the milk of woman, the lactoscope would not be subject to the above fallacy.

Having now shown that the globules constitute an important element of the milk, and the methods by which their number may be ascertained, we may, in the next place, describe more particularly the qualities of good milk.

Healthy milk may be defined to be an alkaline fluid, having a specific gravity of about 1 : 032, holding in suspension numerous perfectly spherical and discrete globules, soluble in ether, and therefore of a fatty nature ; and, in solution, cheese and sugar, together with various salts.

If, on the contrary, the milk be viscous or acid — if the globules be ill-formed or few in number — if they adhere together in masses, and do not roll freely and separately in the serum — if also this contain the colostrum corpuscles — then the milk is either imperfectly elaborated or diseased.

Whenever the proper globules of the milk occur abundantly, are of the usual size, and are equally diffused throughout the serum, we may conclude that the other nutritive elements of the milk are likewise present in due proportion. (See Plate XIV. fig. 1.)

It must be held in mind, however, that the milk of different animals does not contain normally the same relative amount of nutritive ingredients: thus, the milk of woman is especially rich in cream, while that of the goat and ass is but poor in that element.

POOR MILK.

Not unfrequently the milk is found to contain a less quantity of globules than ordinary : the milk in which a deficiency of its globular element exists appears watery and transparent, and is also usually of greater specific gravity than good milk. (See Plate XIV. fig. 2.)

This condition of the milk is one of its most common as well as most serious states in its consequences to the child.

At the same time that the milk is poor in globules or in cream, the serum may be either deficient in quantity, or it may be in excess.

In either case, such milk, whether it be human or not, is deficient of the amount of the nutritive ingredients necessary for the growth and development of the child, which, instead of increasing in size, daily diminishes, becoming faded and emaciated. In the instances in which milk containing a super-abundance of serum is received into


MILK. 213

thj stomach, that organ becomes distended and weakened by its engorgement with a fluid, the digestion of which brings with it little or no nourishment.

An infant whose strength is reduced by the poverty of the milk given to it, is not unfrequently the subject of diarrhoea, which still further lessens its powers.


An opposite condition of the milk to that just described frequently exists, viz : that in which its nutritive principles are in excess, a fact which is most readily ascertained by an examination of the state of the globular element of the milk: this being super-abundant, it may, as already shown, be concluded that the sugar and cheese likewise occur in unusual quantities. (See Plate XIV. fig. 5.)

This condition of the milk is not to be regarded as an alteration of its qualities, but merely as an exaggeration of them ; nevertheless, it is one which is often incompatible with the well-being of the child. This rich milk is often too strong for the digestive powers of the child, whose nutrition in consequence suffers: it, moreover, is sometimes the occasion of colic and diarrhoea.

The state of the milk just noticed, and its consequent effects upon the child, may be modified, and even entirely remedied, by a judicious regulation of the diet, as well as by permitting the milk to remain in the breast for a considerable time, the effect of which retention is to render it more watery; the infant, also, should not be allowed to take the breast except at long intervals.

At the same time that the globules are more numerous in milk which is rich, they are also larger. The size of the globules is likewise found to undergo an increase from the first days of lactation, and this increase continues for some months afterwards : thus, the globules of the third month are larger than those of the first month, and those of the sixth month still larger, the number of the very small globules having diminished very considerably. The increase in the size of the globules referred to, is not, however, so uniform or so constant as to allow of the determination from it of the age of the milk.

ADULTERATIONS OF MILK.

There are but few articles of general consumption more adulterated, and on which more frauds are practised, than the milk. The more usual substances employed for the purpose of adultera


214 ORGANIZED FLUIDS.

tion are water, flour or starch, chalk, and the brains of sheep; of these, water is the one which is most frequently had recourse to, and which is the most difficult to detect.

The effect of water in altering the specific gravity of milk has already been referred to ; and it has been shown that the result of its addition to milk, a portion of the cream of which has been abstracted, is to restore the specific gravity which usually belongs to it.

Donne has shown that, however much the gravity of milk may vary, the density of the serum of the milk is almost constant. This fact is interesting and important; for, by a knowledge of it, the deterioration of milk by its admixture with water, or with some other substance of the same density with it, may be ascertained. The serum is constantly heavier than water; adulteration with it would then cause the serum to exhibit a less specific gravity than that which should properly characterize it; the conclusion to be deduced from this circumstance being that the milk has been deteriorated, most probably, by the addition of water.

The adulterations with flour and sheep's brains are readily detected by means of the microscope. The fraud by the former may be recognised by the peculiar form of the flour granules, as well as by the action of iodine upon them (See Plate XV. jig. 6) ; and that by the latter may be distinguished by the detection, in the fluid, of more or less of cerebral structure, and especially of the nervous tubuli.

The chalk in the milk is readily revealed by its effervescence with hydrochloric acid, as well as by its weight, which causes it to subside at the bottom of the vessel containing the milk.

FORMATION OF BUTTER.

Several explanations have been proposed with the view of determining the exact cause of the amalgamation of the cream globules with each other, and the formation of butter.

Some have supposed that the trituration to which the globules are subject in the churn, determines their union and incorporation with each other ; but it is known that the amalgamation is not a gradual process, as it would be were their union to depend upon trituration, but that it takes place in a manner almost instantaneous: moreover, agitation might fairly be presumed to have a contrary effect on the globules, which participate in the properties of oil, and that it would cause their further sub-division.

A second hypothesis conceives that a chemical alteration in the


MILK. 215

condition of the globules is determined by the presence of the air: this has been shown to be erroneous by the fact that butter will form in vacuo.

A third theory presumed that an acid state of the milk always preceded the formation of the butter : this notion is disproved, since butter is formed of cream, the alkalinity of which is purposely preserved by the addition of soda or any other alkali.

Donne thus explains the formation of butter : " The butter globules," he says, "are surrounded in the cream by cheese in a viscous state: this matter isolates the globules the one from the other, and is opposed to their union. The churning coagulates the cheese in which the globules are imbedded, and, once separated from this, the grease globules unite and agglomerate together easily."

It is doubtful how far this explanation, though more satisfactory than its predecessors, really accounts foi\the instantaneous formation of the butter.

MODIFICATIONS EXPERIENCED BY MILK ABANDONED TO ITSELF, AND IN WHICH PUTREFACTION HAS COMMENCED.

The first change which the milk undergoes, subsequent to its abstraction from the system, is that which has already been referred to, and which consists in the separation of the globular or buttery element of the milk from its other constituents, and its ascension to the surface of the fluid, where it forms the layer of cream; this change in the arrangement of the components of the milk is determined by the lighter specific gravity of the proper milk or butter globules.

All the milk globules do not, however, ascend and join those which constitute the cream : it is chiefly the larger ones which do so, the smaller remaining diffused through the subjacent milk, to which they impart the degree of opacity which belongs to it.

These smaller globules are not, however, equally scattered through the skimmed milk, the greater portion of them being spread through the upper stratum of it, and the lower appearing almost clear and transparent, containing but few butter globules, and these the smallest, as well as the minute cheese globules already described.

These changes consist merely in a different disposition of the normal constituents of milk, and are unaccompanied by any alteration in the constitution of its elements. The next series of alterations have reference to the decomposition of the milk, and are attended by changes in the actual state and composition of the milk.


216 ORGANISED FLUIDS.

The first change experienced by the milk, indicative of commencing decomposition, is that from an alkaline to an acid condition. This acidity, slight at first, goes on increasing, until at length other alterations are produced; thus, the layer of cream becomes thicker and thicker, condenses itself into a mass, and finally presents almost the appearance of butter; at the same time the cheese is coagulated, and precipitates itself to the bottom of the liquid: a portion of it, however, frequently remains suspended in the milk, in consequence of its retaining a number of butter globules, which lessen its specific gravity. Soon, however, other changes show themselves, still more indicative of putrefaction: the layer of cream swells up, becomes more yellow, and a fungus springs up upon its surface, the Penicillum glaucum. This at first presents the appearance of white velvet ; but afterwards, as soon as the fungus has reached the period of fructification, it assumes a green colour.

The idea of M. Turpin, that this fungus had its origin in, and was developed from, the milk globule, scarcely requires a serious refutation.

At the same time, the odour of the milk undergoes a complete change : sweet when it is fresh, it becomes acid as it decomposes, and gives out more especially the smell of cheese.

Examined with the microscope, in addition to the fungus alluded to above, numerous infusory animalcules will likewise be detected.

Now, the changes above described, and which are experienced by the milk of every animal, will be more clearly understood if the milk be previously filtered, and the butter and the serum being obtained separately, those alterations which ensue in each be noticed.

It will be observed, that it is the butter, or non-azotised substance, which undergoes the acid fermentation, and on which the fungi are principally and most generally developed.

The serum, on the contrary, becomes alkaline, and exhibits the ammoniacal or putrid fermentation, this depending upon the azotised principle which it holds in solution, viz : the cheese.

It will be remarked, also, that the serum, in changing, does not exhibit the striking odour of cheese which the milk itself gives out under the same circumstances, and from which it may be concluded that a certain amount of butter is necessary to produce the peculiar smell of cheese.

The phenomena to which the putrefaction of milk give rise result, then, from two kinds of fermentation ; the acid, in which the buttery element of the milk is concerned, and the alkaline, resulting from the decomposition of the caseine.


MILK. 217

THE OCCURRENCE OF MEDICINES, ETC., IN THE MILK.

The extreme rapidity with which the formation of milk from the blood is effected is most surprising, and is only equalled in the animal economy by that with which the urine is itself secreted.

The rapid secretion of milk from the blood serves to explain the almost immediate appearance in the former fluid of various chemical reagents and articles of food introduced into the system through the medium of the stomach.

Thus, many articles taken as food, or as medicine, have been detected in the milk a few minutes after they have been received into the stomach. The colouring matter of madder-root, the odorous principles of garlic, turpentine, &c. — neutral salts, nitrate of potassium — have all been encountered in the milk.

These particulars show the necessity of great precaution in the prescribing of remedies for a nursing mother, and explain the great susceptibility of children at the breast to the influence of the medicine administered to the parent.


[Farther than the directions already given for the examination of Lymph, Chyle and Blood, it is not thought necessary to add any instruction for the study of the fluids just treated of, the manner of preparation and examination being precisely the same, and the different reagents most striking in their effects having been fully indicated in the text.

The preservation of most of the fluids will be found a difficult matter, as most of the preservative solutions employed would so act on the constituents of each fluid, as to render them comparatively useless. The corpuscles of the blood are easily preserved in the manner indicated at the close of the chapter on that subject.

Those of lymph, chyle, mucus, pus, and milk, are best preserved in the flat cell with the naphtha-water, or with Goadby's B-solution, in the manner already indicated in the chapter on preservative fluids.

With all possible care, however, these preparations will soon lose their value, as the corpuscles will undergo more or less change, and therefore cease to have the same characters, as fresh specimens of the same fluid.]


Article VI. — The Semen

The seminal fluid, arrived at its perfect state, as when it is ejaculated, is not a simple liquid, the secretion of a single organ, but is compounded of the several products furnished, though not in an equal proportion, by the testicle, the epididymis, the vas deferens, the prostate gland, the glands of Cowper, the vesiculae seminales, and the follicles of the urethra.

But the spermatic fluid is also in another sense a compound product; thus, like the fluids which have already been described, it is made up of a liquid and a solid element, the latter consisting of numerous organized particles suspended in and diffused through the former ; these particles are of more than one kind, and may be divided into those which are essential and those which are non-essential: those which belong to the first category are the spermatozoa, the seminal granules, and the spermatophori; and those which appertain to the second, are the mucous corpuscles and epithelial scales : these last constituents occur but seldom, and are difficult to discriminate from the seminal granules and the spermatophori.

The spermatic fluid, resulting from the above combination of solid and fluid elements, is then usually a thick semi-opaque and gelatinouslooking substance, of a grayish, whitish, or yellowish tint, and endowed with a peculiar and penetrating odour, which Wagner states does not belong to the sperm previous to its departure from the testicle itself.

It is, above all, the spermatozoa, from the liveliness of their motions, the variety of their forms, the peculiarity of their developments, and their functional importance, which impart interest to the study of the spermatic fluid, and which the microscope has shown to occur in it in such vast numbers.

SPERMATOZOA.

The spermatozoa* are the most distinctive, as well as the most interesting, constituent of the semen, and once detected, the nature of the fluid under examination can no longer be doubted.

  • In reference to the discovery of the spermatozoa, the following passages are contained in Leeuwenhbek (Opera, t. iv. p. 57) : "N. Hartsoeker (Prccven der Doorsichikunde, s. Specimina dioplrices, p. 223) says that he made known the spermatic

animalcules in 1678, in the "Journal des Savants." I attribute the discovery to


THE SEMEN, 219

Each spermatozoon consists of two portions, an expanded part, to which has been assigned the several names of "disc,"' "head," and "body," and an attenuated extremity, which is called "tail."

The spermatozoa present great varieties in size and form: these variations are, for the most part, constant in a natural family and genus, and are always so in a simple species : thus, a knowledge of the particulars of form and size of the seminal animalcules is frequently sufficient to distinguish many groups, genera, and individuals from each other: spermatozoa are, therefore, capable of affording assistance in classification.

Form.

In the class Mammalia especially, with which, in this paper, we are chiefly concerned, the spermatozoa vary greatly in shape; but in several of the more natural groups of that class, one determined form and magnitude may be detected throughout the different species constituting such groups.

In man, and in some animals which approach near to man in their organization, the spermatozoa are small, the head or disc is ovate, the narrow extremity forming the summit of the disc, and the tail, proceeding from its broader end, diminishes in size from its origin to its termination, which is so fine, that its extreme point can with difficulty be discerned. (See Plate XVI. fig. 1.)

In the rat and m the mouse the seminal animalcules are large, and their form peculiar ; the head is half sagittate, and moveable upon the tail, which is long, and attached not to the base of the arrow-like head, but to its side: frequently the head is curved, in which case it resembles the blade of a curved cimeter. (See Plate XVII.)

In the guinea-pig, also, the magnitude of the spermatozoa is great, and the shape remarkable : in this animal the head is large, ovate, concave on one side, and convex on the other, the tapering and elongated cauda arising from the narrow end of the oviform head, which may be compared in form to a mustard-spoon. (See Plate XVII.)

Hamm. He brought me, in 1677, some gonorrhoea! matter, in which he found animalcules with a tail, which, according to him, were produced by the effect of decomposition. I afterwards examined fresh human semen, and I then perceived the same bodies. They were in motion, but in the liquid portion; in the thick part they remained immoveable. They were smaller than the corpuscles of the blood, rounded, obtuse before, pointed behind, with a tail five or six times as long as the body." The description of Leeuwenhoek appeared for the first time hi the Philosophical Transactions, December, 1677, and January and February, 1678.


220 ORGANIZED FLUIDS.

In birds, two singular types occur, the one characteristic of the order Passeres, the other typical of the Rapaces, Scansores, Gallince, Gralla, and Palmipedes. In the first, the head of the spermatozoon is elongated and spiral, resembling a corkscrew; the number of coils and the acuteness of the angles vary in different species ; usually two, three, or four turns are described; the attenuated and greatly produced tail proceeds from the finer end of the spire, and between it and the body no exact line of demarcation exists. (See Plate XVI. Jig. 2.) In the second, there is a distinct division into head and tail, and the former is elongated, as in the order Passeres; but, in place of being spirally coiled, is straight; the tail, arising abruptly from the body, is of great tenuity, of equal diameter, and the length exceeding but little that of the body.

The various forms assumed by the spermatozoa among the other vertebrate and invertebrate animals, it is unnecessary here to describe : the shape of those, however, belonging to the Tritons and Salamanders, from their great peculiarity, may be briefly noticed. At the junction of the body and tail of each spermatic animalcule an enlargement exists, the excessively attenuated caudal extremity being curved spirally round the body.

The effect of water in modifying the form of the spermatozoa is remarkable, it frequently causing them, when applied in large quantities, to coil up and form themselves into rings : this effect of the application of water is supposed to depend upon some hygroscopic property possessed by the spermatozoa.

Frequently the spermatozoa are seen to occur on the field of the microscope, grouped together in bundles, the bodies all lying one way, and fitting by their concavities into each other. (See Plate XVII.) This arrangement, as will be seen hereafter, is connected with the evolution of the spermatozoa.

Occasionally, in man and other animals, the head and tail are separated from each other, and lie apart; this separation is doubtless either the result of violence or the effect of decomposition. Henle* states that he has seen the tail move independently of the head.

Size.

Much diversity exists in the size of the spermatozoa in different animals, although but little difference can be detected in those of the same individual. Wagner, however, has made the observation that

  • Ajiat. Gen. p. 534.


THESEMEN. 221

their magnitude varies greatly in different individuals of the same species. These variations are, however, of course, confined within certain narrow limits. In the Mammalia, the spermatozoa of man are among the smallest, while those of the guinea-pig and rat are among the largest hitherto discovered. . In the birds the seminal animalcules of the order Passer es are very large, and especially those of the chaffinch.

Structure.

When first the spermatozoa were discovered, and their lively motions observed, much reluctance was entertained to regard them as independent animals or beings; and upon this point, even among modern physiologists, there is still an absence of accord, some of them attempting to explain the movements exhibited on purely physical principles.

Not many years ago, a celebrated and talented continental observer thus expressed himself, in terms more ingenious than accurate, in reference to the nature of the spermatozoa:

"When we place upon the object-glass of the microscope the semen of a subject who enjoys all the energy of his generative faculty, we there see corpuscles more or less rounded or oval, having a sort of caudiform appendix : some have made animalcules of these little bodies, since they have seen that they move, and have believed to have recognised in their movements a determined direction, a character which they thought could only appertain to animated beings. And as among the microscopic animalcules which they knew there are those which are provided with a tail more or less prolonged and more or less dilated, they have assimilated to them the little animalcules of the semen, and have made them Cercarice.

"But you are about to see that the conformation and the movements of the corpuscles in question may be explained naturally, without our being obliged to have recourse to the hypothesis of which I have spoken. It is certain that we find in the sperm little gelatiniform masses, more or less rounded, oval, and having one part prolonged into the form of a tail, like, in a word, to the drawings which Buffon and many other observers have given us of the pretended spermatic animalcules. These little masses float in a material less consistent than themselves, and even fluid. But at first their oval form results evidently from the manner in which they reflect the


222 ORGANIZED FLUIDS.

light, and afterwards as the fluid in which they are suspended — a fluid which is itself more or less viscous — attaches itself strongly to them, it results that in the microsco-chemical movements which take place in the sperm, the corpuscles which it encloses seem to have a tendency to escape from the kind of glutinous material which contains them. This material, seeking, if we may express it thus, to retain them, accompanies them to the situation only where they find themselves to be arrested by a filamentous prolongation, which presents sufficiently well the appearance of a tail, and even of a flexible tail, by reason of the lateral movements which the little body makes in its progression. There is merely in all this, as you see, a mechanical phenomenon, and, in the movement which there takes place, but a physical effect of the contact of two materials of different densities ; contact which provokes these materials to mingle together and to form but one, as arrives at the end of a time more or less long. Abandon the semen to itself, taking care that its watery part cannot evaporate by placing it in an atmosphere saturated with humidity, at the end of a certain time the mixture of the two materials will be complete, and you will perceive no longer any thing but a homogeneous fluid; the pretended animalcules have disappeared.

"If we wish to show you at the same time veritable microscopic animalcules and the little gelatiniform masses which move in the vehicle of the sperm, you will find a great difference between the first and these last. I may fortify my opinion on this subject with that of Buffbn and Spallanzani, who have denied that the masses of which I speak w r ere animalcules.

"Among the persons who have admitted the existence of these beings, there are those who have carried their pretension so far as to class them in genera and species by taking the form of the dilated extremity for the principal zoological character. Some micrographers, also, remarking the differences in the corpuscles of the sperm, according as one procures this liquid from the testicle, the vesiculse seminales, or after its ejaculation, have pretended, from that circumstance, to describe a series of evolutions in the development of these so-called Cercarice. They have told us that these animals do not exist in the product which occupies our attention at the moment that it is formed; that they appear but in the vesiculae seminales; that in these they are as yet but simple globular animals; that in their progress they become developed by the production of their caudal prolongations. Lastly, it has been pretended — doubtless with the


THE SEMEN. 223

design of marking with ridicule the opinions which we have reported — it has been pretended, I say, that the spermatic infusorias became among us, for example, veritable homuncules, having little arms, little legs, &c. But this is sufficient in itself to put us on our guard against an optical illusion which has unfortunately seduced a great number of persons, from Leeuwenhoek, one of its first favourers, even to MM. Prevost and Dumas, who in these latter days have still maintained the existence of the spermatic animalcules."

In the present day, it is needless to enter into any refutation of the above views ; it cannot, however, fail to be observed by the reader, that they are weakest just where they should exhibit the most strength, that is, in the explanations given as to the form and motions of the spermatozoa.

Those physiologists who deny the animality of the spermatozoa would, of course, be very reluctant to admit of the existence of any thing like organization in them; while those, on the other hand, who entertained a belief in their animal nature, would be most anxious to establish the fact of such organization.

The greatest possible difference of opinion, then, exists as to whether the spermatozoa are organized or not, and, if organized, as to the extent to which they are so.

In the centre of the disc of the spermatozoa of man and some other animals a light spot has been observed ; this some have imagined to be a stomach; others, again, have rejected this idea, and thus account for its presence : the disc, they say, is not ot equal thickness, and, like the red blood corpuscle, is thinnest in the centre, and which part, therefore, exhibits a lighter tint than the remainder: this latter view is most probably the correct one. The first opinion is entertained by Valentin, and the second by Dujardin and Henle. Miiller conceived the spot in question to be a nucleus.*

Leeuwenhoek remarked upon the spermatozoa of the ram two clear spots; at another time, numerous little points in the interior; a third time, two semi-lunar striae, united by a longitudinal line; he figures also in those of the rabbit a multitude of little globules — one of them, larger than the rest, being placed near the tail.

Gerber assigns a most complex structure to the spermatic animalcules of the guinea-pig, describing stomachs similar to those of the poly gastric infusorise, an anus and sexual apparatus; and conceiving

  • Muller's Physiology, p. 635.


224 ORGANIZED FLUIDS.

the existence of these several parts to have been established, he thus expresses himself in reference to the nature of spermatozoa in general : "The compound organization of the seminal animalcules and their production by no equivocal generation, but in particular sexual organs, and by the means of ova, to all appearance proclaim their affinity to the Entozoa."*

Valentin f has described an almost similar amount of organization in the spermatozoa of the bear: "The clear spermatozoa of the bear," he writes, "which in external form approach those of the rabbit, present distinct traces of internal organization, to wit, an anterior and posterior haustellate mouth, and internal cavities or convolutions of an intestine."

Again, Dujardin J has described and figured certain irregular knots and lobular enlargements at the root of the tail of the human spermatozoa; these have been noticed by Wagner, who believes that they occur only as the effects of certain alterations experienced by the animalcules in consequence of their long stay in urine, and especially when this fluid has contained at the same time a quantity of puriform sediment.

Wagner likewise points out, as occurring now and then, but by no means constantly, a small prominence or trunk-like process situated on the anterior part of the body of human spermatozoa: this, or a similar projection, he also states to be much more regularly present in the seminal animalcules of the bat, in which they occur as pointed spines. The same observer has, moreover, noticed upon one or two occasions the caudal end of the body to be double, bifid, or forked, and once too the body appeared to be double, as in a bicephalous monster.§

The above comprise all the particulars which have hitherto been promulgated in reference to the organization of the spermatozoa; scarcely any one of them has, however, been sufficiently established : we are therefore not authorized to receive them as proved, and to build any reasoning upon them : the most which we are warranted in deducing from them amounts to this, that traces of organization have been discovered in the spermatozoa, the precise nature and extent of which have not as yet been satisfactorily determined.

  • Gerber's General Anatomy, translated by Gulliver, p. 337.

f Repertorium, 1837.

I Ann. des Sciences Nat. viii. p. 293. plate 9. 1827.

§ Elements of Special Physiology, pp. 10. 16.


THE SEMEN. 225

Notwithstanding his observations, given above, Wagner* states that he has been utterly unable, after varied, repeated, and longcontinued examination, to discover true internal organs in the spermatozoa. Sieboldf has also been equally unsuccessful in his endeavours to detect such, as also HenleJ and Koelleker.

The determination of the fact that the spermatozoa are possessed of even the smallest amount of organization, would involve their classification in the animal kingdom, and the description of the different forms which occur as so many distinct species.

The view of the animal nature of the spermatozoa would appear to gather strength, and to admit almost of positive demonstration, by reference to their very remarkable motions.

MOTIONS OF THE SPERMATOZOA.

It is impossible that any thing can convey a more just idea of life than the spectacle of a drop of the seminal fluid in which the spermatozoa are in active and ceaseless motion.

Sometimes, indeed, when the semen is thick and tenacious, the movements of the contained spermatozoa are but feeble, the density of the liquor seminis presenting too great an impediment to the free motion of these minute creatures.

Often, however, in such cases, when the fluid has been diluted with water or with some other liquid, as serum or milk, of less density than itself, the spermatozoa, being now set at liberty, will frequently be seen to resume their locomotive powers, and to move about with the greatest activity. All the spermatozoa, however, contained in a drop of semen which has undergone dilution will not start into motion at once; many of them will remain for a time perfectly motionless, and then suddenly, and, as it were, by an act of volition, begin to move themselves in all directions.

Mode of Progression.

The motions of the spermatozoa are effected principally by means of the tail, which is moved alternately from side to side, and during progression the head is always in advance.

The strength of the spermatozoa is considerable, it enabling them, when they are immersed in either blood or milk, to cast aside, with

  • Loc. cit. p. 17. f Siebold in Weigman's Archiv. 1838.

\ Anatomie Generate, t. vii. p. 531. 15


226 ORGANIZED FLUIDS.

the greatest ease, the globules which may present themselves to impede their progress.

The spiral spermatozoa of the Passeres advance by a movement of rotation of the body, the tail remaining extended and motionless, acting rather as a rudder than as an organ of locomotion. The spermatozoa of the other orders of birds, and which consist of a cylindrical body to which a short and attenuated tail is attached, "scull themselves forward with their tails, either striking them slowly and with wide sinuosities, or more quickly and shortly, as when a whip is shaken ; they thus advance in circles with a quivering motion, holding the body extended in a straight line, although they also now and then bend this in various directions from side to side."*

The spermatozoa of the tritons and salamanders usually lie coiled up in the form of a ring, and seem to spin round as upon a pivot ; at the same time a second wavy and tremulous motion, like that produced by cilia, is observed; this arises from the rapid rotatory or spinning movement of the very delicate tail with which the spermatozoa of these animals are furnished, and which is wound spirally round the body. Wagner at one time entertained the notion, which, however, he subsequently discarded, that the wavy motion referred to was produced by a ciliary apparatus. Sometimes the coiled spermatozoa have been seen to unrol themselves and to cross the field of the microscope with slow serpentine motions.

Furthermore, in the various motions executed by the spermatozoa, they exhibit all the characters of volition; thus they move sometimes quickly, at others slowly, alter their course, stop altogether for a time, and again resume their eccentric movements. These movements it is impossible to explain by reference to any hygroscopic properties which may be inherent in the spermatozoa, they appear to be so purely voluntary. A strong argument, therefore, in favour of the independent animality of the spermatozoa may be derived from a consideration of the nature of their motions.

Duration of Motion.

The length of time during which the motions of the spermatozoa continue, either after the escape of the seminal fluid, or after the death of the animal, varies very considerably; thus it is maintained, for a longer period in warm weather than in cold, and when the semen is retained within its natural reservoirs than when it is

  • Wagner's Elements, p. 18.


THE SEMEN.


227


removed from those receptacles. The spermatozoa of some animals also preserve their powers of locomotion for a longer period than those of others ; thus, the seminal animalcules of birds die very soon after the death of the bird; according to Wagner, frequently in from fifteen to twenty minutes;* occasionally, nevertheless, the spermatozoa have been found moving in birds which have not been opened until some hours have elapsed after death: those of the Mammalia have been observed in motion for a very long period after the removal of the semen from the testicle, and after the death of the animal; but it is in fishes that the spermatozoa retain their powers of locomotion out of the body for the longest period, even for many days.

According to Dujardin,f the spermatozoa live thirteen hours in the testicles of the mammalia after the death of the animal.

LamperhoffJ has found living semen in the vesiculse seminales of dead men, in which the spermatozoa retained the power of locomotion for twenty hours.

Wagner§ has observed them exhibiting motion at the end of twenty-four hours.

Donn6|| states that he has watched their movements for an entire day, and that he has observed them in motion even on the second day.

It is, above all, in the place of their final destination that the spermatozoa live for the longest period ; thus, Leeuwenhoek first, and other observers subsequently, have discovered them in a living condition in the uterus and Fallopian tubes of a bitch seven days after connexion,^! and Bischoff** has found them alive eight days after intercourse in the rabbit.

The great length of time during which, under certain circumstances, the spermatozoa retain the faculty of locomotion, furnishes another strong argument in favour of their independent vitality.

Effects of Reagents.

The seminal animalcules retain their locomotive powers for a very long time in fluids of a bland nature ; for example, in blood, milk, mucus, and pus ; on the contrary, in reagents of an opposite character, and in those possessed of poisonous properties, they soon cease to move : thus, in the saliva and urine, unless these fluids be very much


  • Wagner, loe. cit. p. 21.

\ Diss, de Vesical. Semin.

II Cours de Microscopic, p. 284.

    • Miiller, Archiv. p. 16. 1841.


f Annates des Sciences Nat.

5 Loc. cit. p. 22.

IT Opera Omnia, 1. 1. b. p. 150.


228 ORGANIZED FLUIDS.

diluted, their motions are soon destroyed, and immediately cease in the acids and alkalies, in alcohol, iodine, strychnine, and the watery solution of opium.

The addition of water to the spermatic animalcules usually produces a remarkable effect, increasing greatly for a time the rapidity of their motions, which after the lapse of a minute or two entirely cease; this reagent, as well as the saliva, exerts a further peculiar influence upon them, causing them to curl up into circles or rings.

Poisons introduced into the system, and destroying the life, are stated not to affect the motions of the spermatozoa; an assertion to be received with some degree of hesitation : in cases of poisoning by prussic acid, I have usually found the spermatozoa to be motionless, even when viewed immediately after death.

The urine has the property of preserving the spermatozoa entire for weeks and months ; and Donne 1 has detected them in that fluid after an interval of three months.

The result, then, of the application of reagents, furnishes an additional argument in favour of the animality of the spermatozoa, and one which it would be difficult, if not impossible, satisfactorily to controvert.

SPERMATOPHORI.

The only essential solid elements contained in the seminal fluid arrived at its perfect state, as in the vas deferens, and when ejaculated, are the spermatozoa; occasionally, however, there are encountered in it, as non-essential constituents, mucous corpuscles, epithelial scales, and the seminal granules : the spermatic liquid, however, obtained from the body of the testicle, contains not only the several structures already named, but also minute and bright granules, and the compound cells or sperm atophori, the bright granules and the seminal corpuscles probably represent stages in the development of the spermatophori.

The several structures now named are all occasionally met with in the ejaculated semen; their occurrence in it is to be regarded rather as accidental than as essential ; the spermatophori belong to the testicle, the tubuli seminiferi of which in many cases are almost filled by them.

The spermatophori differ greatly from each other, both as respects size and the number of secondary cells or nuclei contained within them ; the smaller parent cells are about TJ \ o °f an mcn m diameter


THE SEMEN. 220

in man, and contain usually but a single nucleus, while the larger ones attain the magnitude of j ±-q of an inch in breadth, and include not unfrequently as many as six or eight nuclei, or, more properly speaking, secondary cells. Between the two extreme sizes given, every gradation presents itself, and many spermatophori contain but one, two, three, or four nuclei, which are the numbers most frequently encountered.

The secondary cells, like the primary or parent ones, are globular, and those contained within the same parent cell are usually of the same dimensions ; the centre of these cells occasionally presents a bright spot. (See Plate XVI. fig. 1.)

Not unfrequently certain large and perfectly transparent cells are encountered; these are, in all probability, the older spermatophori, the contents of which have been discharged.

It would appear, therefore, that the development and dissolution of the spermatophori are effected entirely within the tubes of the testes.

Cells, which Wagner has denominated seminal granules, occur, as already remarked, mixed up with the undoubted spermatophori ; these first are smaller, and do not contain nuclei; whether they are really distinct from the latter, it is not easy to determine. If but one kind of cell occurs in the testicle, then a double function must be assigned to it : thus, in the first place, the secretion of the liquor seminis must be effected by it ; and, in the second, the development of the spermatozoa occurs within its cavity; in which case the spermatophori would be the homologues of the cells of other glands, only in so far as they discharge an analogous function, and are secreting organs ; in the ulterior office allotted to them, that of being receptacles in which the spermatozoa are evolved, they stand alone in the animal economy, and are certainly without analogues in any other gland of the body.

It is most probable, however, that two kinds of cells coexist in the testes — the one secreting and corresponding with the cells of other secerning organs ; the other kind, of a peculiar nature, without parallel in the animal economy, and devoted to the development of the spermatozoa.

DEVELOPMENT OF THE SPERMATOZOA.

Not the least interesting part of the history of the spermatozoa is that having reference to their development.

Wagner was the first to state that the spermatozoa are developed within the spermatophori just described.


230 ORGANIZED FLUIDS.

This interesting discovery of Wagner has been amply confirmed by the extended observations of Kcelliker, Siebold, Valentin, and Lallemand.

Wagner thus describes the evolution of the spermatic animalcules in the spermatophori of a bird : " In the course of their development, a fine granular precipitate is observed to form between the included nuclei, by which these are first obscured and then made to disappear, and linear groupings are produced, which anon proclaim themselves as bundles of spermatozoa, already recognisable by slight traces of a spiral formation of one extremity. (See Plate XVI. fig. 2, g.) It were hard to say whether the fine granular precipitate is to be regarded as the product of a process of resolution occurring to the nuclei, or a new formation ; as, also, whether the spermatozoa spring out of or only in and amidst the yolk-like matter, or matter that is at all events comparable to the yolk of eggs in general. The vesicles now assume an oval form (see Plate XVI. fig. 2, h), the globules disappear, the granular contents diminish; the seminal animalcules are well grown, and lie bent up within the cyst ; their spiral ends are more conspicuous. The delicate covering (involucrum) is now drawn more closely around the bundle of spermatozoa it includes, and where it covers their spiral ends anteriorly it assumes a pyriform outline (see Plate XVI. fig. 2, i), and at the opposite extremity is perhaps at this time open ; but it is difficult to speak decisively on this point. The cysts are now very commonly bent nearly at right angles or like knees, but at length they appear stretched out and straight, and have attained their full size. (See Plate XVI. fig. 2, k.) The capsules of these vesicles are at all times, and especially towards the end of their existence, highly hygroscopic; the addition of a little water causes them to burst, the masses of spermatozoa rolled up like a little skein of thread or silk escape, and occasionally at this stage exhibit motions individually, which, however, while the. animalcules continue in the ducts of the testes, are frequently not to be observed, and are never either general or remarkable. The spermatozoa, after the rupture of the cyst, advance in freedom to the vas deferens."*

The process Wagner states subsequently to be precisely similar in man and the Mammalia, although it is more difficult to follow it in them.

The accuracy of the above account of the development of the spermatozoa has been admitted by most other observers in all respects

  • Translation of Wagner's Elements, by Willis, pp. 25, 26.


THE SEMEN. 231

save one important one: thus, Koelliker has shown that the evolution takes place in the included or secondary cells, and not, as Wagner describes it, in the spaces between these, a single spermatic animalcule being formed within each ; the granules enclosed in these cells disappear gradually as the spermatozoon assumes a definite form, and Koelliker further supposes that these granules constitute, by their union with each other, the substance of the spermatozoa which escape from both the secondary and primary cells by the rupture of their investing membranes. When the spermatic animalcules have escaped from the secondary cells, and these have disappeared, the spermatozoa form a bundle which is still included within the larger primary cell ; sometimes the seminal animalcules are irregularly disposed within its cavity, but more frequently they are applied directly to each other, the heads lying one way, and the tails in the opposite direction. This disposition of them is often preserved even after their escape from the spermatophori, during their stay in which the spermatozoa usually remain quite motionless.

The interesting and important fact of the development of the spermatozoa in the secondary cells, or ova, as they should now be called, Koelliker first ascertained by the study of their evolution in the guinea-pig;* subsequently, he extended his observations, and found that the spermatozoa in man were evolved in a manner precisely similar.

Valentinf during his inquiries observed masses of filaments in the mother cells of the rabbit and bear, and Hall man J noticed the same thing in those of the rays ; he does not, however, speak of the transformation of the included nuclei or ova.

In the class of invertebrate animals, it is most probable that a similar method of development prevails.

The spermatozoa are not encountered in equal numbers in all parts of the testicle, the more remote convolutions of the tubuli seminiferi containing chiefly the simple granular cells and the spermatophori, while it is only in those which approach near to the epididymis that they occur in any numbers; in this situation they usually lie immediately beneath the membrane of the seminiferous tube, and external to the spermatophori, their long axes being disposed in the direction of that of the tube itself. In the vas deferens the spermatozoa are pres

  • Beitrag. p. 56. tab. 11. fig. 20. f Repert. p. 145. 1837.

\ Muller, Archiv. p. 471. 1840.


232 ORGANIZED FLUIDS.

ent in vast numbers, and with scarcely any admixture of the other solid elements of the testes.

It is in the epididymis that the different stages of development of the seminal animalcules are best seen side by side.

The spring is by far the most suitable period for the study of the development of the spermatozoa, and birds, especially those of the order Passeres, present the best examples in which to trace their evolution, because in them the seminal animalcules are large, and the reproductive function is excessively active for a brief and determined period.

Wagner* has shown that from the commencement of the time of moulting, and through the entire winter, the testes of birds undergo an extraordinary degeneration, the spermatozoa and the spermatophori being entirely obliterated, and the volume of the testes reduced to at least the twentieth or thirtieth of the size to which they attain in spring. Thus, the testis of the common chaffinch is in winter not larger than a millet-seed, while in spring it exceeds a pea in size.

The same degeneration is doubtless experienced during winter, although to a less extent, by most animals of the class Mammalia.

THE SPERMATOZOA ESSENTIAL TO FERTILITY.

The spermatozoa do not exist in the testes of mammalia at all periods of life : thus, they do not make their appearance in that organ in man until the period of puberty, and they disappear gradually as old age advances. It is impossible, however, to determine the time at which they are first developed, or at which they cease to exist in that organ, because the period of puberty differs in different individuals, and some men are aged in constitution when others of the same years are hale and robust. Certain it is, that some men retain the power of engendering until a very advanced age, of which fact the celebrated Parr presents a memorable example, he having become a father at the extraordinary age of 142.

The number also of the spermatozoa contained in the seminal fluid varies in different individuals, and is usually in proportion to the activity of the reproductive function, and this again is dependent to a great extent upon the constitutional powers as well as upon the mode of life.

The activity, then, of the reproductive faculty in man is in many cases a good test of health.

The above few facts favour the idea of the essentiality of the

  • Elements, pp. 28 and 29.


THE SEMEN. 233

spermatozoa; others, however, of a stronger kind, still remain to be mentioned.

Wagner has instituted some most interesting inquiries in reference to the condition of the spermatozoa in male hybrids, and especially in ma^e hybrid birds, and he finds, that in them the characteristic animalcules are either altogether wanting, or occur but in small numbers, and are ill-formed and ill-conditioned; the hybrids in which the seminal animalcules have been thus found to be absent or degenerated, have been ascertained to be incapable of having offspring.*

Again, Leeuwenhoekf discovered living seminal animalcules in the uterus and Fallopian tubes of bitches seven days after connexion. J

Prevost and Dumas§ have more recently made the same observations at the same length of time after intercourse.

Siebold|| has detected the spermatozoa in a living state in the uterus and Fallopian tubes eight days after connexion. snj

Lastly, BischoffTl and Martin Barry** have observed the spermatozoa not merely in the uterus and Fallopian tubes, but also on the ovary itself.

From these facts it is therefore evident that the spermatozoa are essential to fecundity, although the precise manner in which they are so is still involved in the greatest obscurity. It is supposed by some observers, that they make their way into the ovum itself: this notion is as yet without evidence to support it.

It would be most interesting to determine whether impregnation could be procured by the artificial introduction of semen, the animalcules of which were dead; there is every reason to believe that in the many cases in which the artificial injection of the seminal fluid has

  • Loc. cit. pp. 30 — 34. f Opera Omnia, p. 150.

\ Leeuwenhoek signalized the discovery of the living spermatozoa in the uterus and Fallopian tubes, in the following words : " Nudo conspiciens oculo, nullum masculum semen canis in ea esse dicere debuissem; at eandem mediante bono microscopio, summse mese voluptati immensam viventium animalculorum multitudinem; semen nempe canis masculum contemplabar. His peractis, dictam aperiebam tubam, in fine suae crassitudinis, ac ibidem quoque magnam seminis masculi canis contemplabar copiam, quod semen illic vivebat, et hoc modo quoque cum dextra egi tuba, ac in eadem quoque immensam seminis viventis canis masculi copiam observavi. . . Materiam qua matrix concita est, observans, majorem adhuc viventium animalculorum copiam deprehendebam."

\ Annales des Scien. Nat. t. iii. p. 122.

|| Miiller, Archiv. p. 16. 1841. IT Wagner's Elements, p. 66.

    • Researches in Embryology, Second Series, Phil. Trans, p. 315. 1839.


234 ORGANIZED FLUIDS.

been successful, the contained spermatozoa were in a living condition; and from all that is yet known in relation to the animalcules, there is strong presumption to believe that the experiment referred to, viz: the introduction of semen, the animalcules of which were dead, would be unattended with success.

One remarkable experiment of Spallanzani, however, deserves to be referred to. Most observers agree in saying, that the spermatozoa of the frog die after some hours of immersion in water. It is known, however, that Spallanzani succeeded in fertilizing the ova of frogs with spermatized water, containing three grainsof seminal fluid to eighteen ounces of water, thirty-five hours after the mixture had been prepared, and this, in a chamber with the thermometer at from seventeen to nineteen degrees; and again, that in an ice-house, the thermometer being three degrees above zero, the spermatized water preserved its prolific power for fifty-seven hours.

Now, the tendency of this interesting experiment is certainly to prove the possibility of fertilization occurring with semen, the spermatozoa of which are dead: this inference would appear, however, to be negatived by another ingenious experiment of MM. Prevost and Dumas, who filtered the seminal fluid, and found that the fluid portion which passed through the filter would not vivify the eggs, while the more solid part, consisting of the spermatozoa, produced the results peculiar to the seminal fluid.

Jacobi succeeded in fertilizing the ova of a carp with semen which had been contained within the body of the fish for four days; but it is well ascertained that the spermatozoa of fishes in general live for a much longer period than that named.* Some have supposed that the only use of the spermatozoa is by their movements to hasten the advance of the semen towards the Fallopian tubes.

PATHOLOGY OF THE SEMINAL FLUID.

The quantity of seminal fluid secreted varies greatly according to the age and constitution of the individual. In young men, and in those whose health is vigorous, the secretion is rapid and abundant; in the aged, and in those whose vital powers are feeble, it is but slow and scanty. It is, however, in severe states of disease that the amount of seminal fluid secreted is greatly diminished, if the formation of it be not in some cases altogether suspended for a time. Under the

  • Several most interesting particulars in reference to artificial impregnation are

given in Wagner's Elements, chap. iii.


THE SEMEN. 235

influence of recovery, the quantity of semen formed again undergoes an augmentation.

An inordinate secretion of the seminal fluid, as also its prolonged retention in the testes, are sometimes the causes of involuntary seminal discharges, which, however, are far more frequently occasioned by organic weakness, the result of over-indulgence.

If these emissions be very frequent, the ejaculated semen will be found to be thin and watery, and to contain comparatively few spermatozoa.

It is unnecessary to describe here the destructive effects of these emissions on the constitution.

It is often a matter of great importance to determine, independently of any revelation on the part of the patient, whether in any particular case seminal effusions exist.

This fact, it is in the power of the microscope, according to some observers, in all cases to declare with the most absolute certainty.

After each effusion of semen, in whatever way occasioned, a certain amount of that fluid will still remain behind, adhering to the surfaces of the urethra; this, of course, contains the seminal animalcules, which will be washed away on the first passage of the urine through the urethra.

The great object, then, is to establish the fact of the existence of spermatozoa in the urine : this may be accomplished in two ways ; either by filtration or decantation, the latter being perhaps the preferable method of the two; the spermatozoa, being heavier than the urine itself, always subside at the bottom of the vessel, and where they may always be found, if present in even the smallest numbers.

The urine, as already mentioned, has the property of preserving the seminal animalcules, which may be detected in it months after their discharge from the urethra.

M. Donne* states, that he has never succeeded in detecting the seminal animalcules in the urine, unless as the consequence of an emission of semen, and which may have occurred either during connexion, in an involuntary manner, or through masturbation. Now, if this be true, the occurrence of the spermatozoa in the urine declares positively the fact, that a discharge of semen has been sustained, and this particular is often in itself sufficient to enable a medical man to form an opinion of the case.

It seems to me, however, by no means sufficiently proved, that an

  • Cours de Microscopie, p. 318.


236 ORGANIZED FLUIDS.

escape of the seminal fluid with the urine does not take place independently of any distinct emission. I am inclined to think that such escape is an habitual occurrence even with the most healthy, especially with the continent, and that by it the surcharged testes are relieved whenever requiring such relief.

This view is to some extent supported by the observations of Dr. John Davy* and Wagner :f the former excellent observer states that on examining the fluid from the urethra after stool in a healthy man, he had always detected spermatozoa.

In connexion with the above few remarks on the pathology of the semen, we may refer to the observations of Donne" on the effects of an exceedingly acid condition of the mucus of the vagina, and a very alkaline state of that of the uterus itself, on the vitality of the spermatozoa.

The mucus of the vagina, in its normal state, is slightly acid, this degree of acidity being perfectly compatible with the life of the sem inal animalcules; but Donn6 has shown that under some circumstances — as from congestion, irritation, or inflammation — this mucus becomes so strongly acid as to destroy in a few seconds the vitality of the spermatozoa.

Again, the mucus of the uterus in its healthy state is slightly alkaline, but not so much so as to exert any injurious effects upon the spermatozoa; in conditions of derangement and disease, however, it becomes so alkaline, as Donne" has shown,J that in like manner with the acid mucus of the vagina, it kills the seminal animalcules in a very short space of time.

Now, after what has been said and detailed in reference to the essentiality of the spermatozoa, it can scarcely be doubted that women whose vaginal and uterine secretions are so disordered, are inapt to conceive, and this from the effect of their vitiated secretions upon the spermatozoa.

It would be interesting to determine whether the spermatozoa are ever entirely absent from the semen of man: it is very probable that in certain rare cases they are so, and from the facts already ascertained there can be no doubt that those individuals whose spermatic fluid is devoid of its characteristic living element, would be wholly incapable of having offspring.

It is probable that in the impotent the spermatozoa are almost, if not entirely, extinct.

  • Edin. Med. Surg. Jour. vol. ii. p. 50. t Loc. cit. p. 21.

t Cours de Microscopie, p. 292.


THE SEMEN. 237

APPLICATIONS OF A MICROSCOPIC EXAMINATION OF THE SEMEN TO LEGAL MEDICINE.

The detection of the spermatic animalcules is frequently a matter of high interest and importance in a medico-legal point of view.

There are three classes of cases in which the microscope, by revealing the presence of spermatozoa, is capable of forwarding the ends of justice, and of bringing conviction home to the guilty.

1st. In cases of suspected violation.

2d. In determining the nature of doubtful stains observed on the bed-clothes, &c.

3d. In unnatural offences.

With respect to those cases which come under the first division, it may be observed that the medical testimony on which these are usually decided is too often of such a nature as to lead to the acquittal of a really guilty individual ; the medical man, judging merely from external appearances, being compelled to give evidence either directly favourable to the prisoner, or which is at best but of a doubtful character.

In suspected violation, then, when the evidence to be deduced from an outward examination is insufficient for the formation of a satisfactory and decided opinion, the microscope may frequently be employed with the greatest advantage.

If the offence imputed has been committed, and if connexion has really occurred, then by means of this instrument, provided too long a time has not elapsed from the period of the occurrence, that is to say, a period not exceeding from twenty-four to forty-eight hours, the spermatozoa will be detected in the mucus, properly examined, and obtained from the upper part of the vagina: now, the detection of these in such a situation is a demonstration that intercourse has taken place.*

The examination of the urine of women whose persons are suspected to have been violated would also frequently furnish evidence of the fact by manifesting the presence in it of the spermatozoa, which in its passage through the vagina it had washed away from its walls.

With reference to the second class of cases mentioned, those requiring for their satisfactory elucidation the determination of the nature of suspicious stains, here again, by means of the microscope, evidence the most conclusive may frequently be obtained.

  • Donne, in the Cours de Microscopie, states that he has detected the spermatozoa in the vaginal mucus of women admitted into the hospital, in which instances it is

most prohable that connexion had occurred at least some hours previous to a dmis sion.


238 ORGANIZED FLUIDS.

Now, if the stains in question be formed by the seminal fluid, and if they be not too old, the microscope applied to them will detect in them the spermatozoa.

With regard to the length of time at which the spermatozoa may be detected in the matter of a stain, I have reason to think that this has scarcely a limit: I have myself noticed them in the semen several weeks old, and they then appeared to have undergone scarcely a single appreciable change, the spermatophori contained in the seminal fluid being equally well seen.

In examining stains occasioned by the seminal fluid, it is advisable to use the same precautions as those which were pointed out in reference to blood stains, and to moisten them with either serum or albumen.

The reader's imagination will suggest to him numberless cases in which the determination of the nature of suspected stains would be a matter of the utmost importance, and would lead to the production of evidence of the greatest consequence, and in no other way obtainable.

Lastly, with reference to the third class of cases, those of unnatural offences: here also the microscope, by revealing the presence of the spermatozoa in the rectum, or on some other part of the body, may throw great light on occurrences which otherwise would in all probability be buried in complete oblivion and mystery.

An examination of this kind was assigned by the magistrates in France some years ago to two physicians, on the occasion of an assassination in a hotel. A traveller having been killed by a young man whom he had received into his chamber during the night, justice was interested to know whether semen would be found in the rectum or not.*

It is known that in death by hanging, an emission of the semen usually occurs, and this, in the absence of other proofs, has been adduced as a sign of death by suspension. It would appear, however that such an indication is not without its sources of fallacy.

It is thus apparent that in the cases here referred to, the microscope is capable of affording positive evidence of a most important and conclusive kind; on the other hand, the negative testimony deducible from its application in these cases is not without its value.

  • See Annates d'Hygiene Publique el de Medecine Legale, Paris, 1839, t. xxi. pp.

168 and 466.


THE SEMEN. 239


SEMEN.

[In making examinations of the seminal fluid, the purest and most concentrated will be found in the vas deferens or epididymis The sooner this is examined after the death of an animal, the less change will be detected, and the motions of the spermatozoa will be most active. If a small drop of the fluid is placed on a plain glass slide, covered with thin glass, and placed in the field of the microscope, many of the spermatozoa will be seen in active motion, with a ith-inch object-glass. It will be found better to dilute the fluid before covering it with the thin glass. For this purpose, albumen, or a little water which has -^\th part of salt or sugar dissolved in it, will answer, or, still better, a little serum of the blood. When properly diluted, the thin glass is applied, as before, and the seminal animalcules will be much better defined than without this dilution. The reagents most striking in their effects have already been pointed out.

PRESERVATION.

The seminal animalcules may be preserved, either in their own fluid, or in a weak solution of salt and water, or of chromic acid. In either case, the flat cell, or the thin glass cell, is to be employed, and the cover cemented with gold-size. In this condition, they will keep for many years.]


UNORGANIZED FLUIDS.

Article VII. — Saliva, Bile, Sweat, Urine

The fluids comprised under the heading of Unorganized Fluids differ from those of the first division, viz: the Organized, in that they do not contain, as essential elements, organized structures; solid organic particles are indeed usually to be encountered in them, but these are to be regarded either as accidental, or at all events as nonessential adjuncts, and which appertain usually to the structure of those organs from which the fluids have themselves proceeded.

The presence and nature of the solids contained in the Unorganized Fluids serve to indicate, to a considerable extent, the condition of the glands by which they have been secreted, and thus frequently throw great light upon their pathology.

There is, however, one kind of solid constituent which is found almost constantly in these fluids, viz: the crystals of various salts: these being, however, unorganized, their consideration does not properly belong to a work devoted to descriptions and delineations of organized tissues.

It is proposed, therefore, in order to render the application of the microscope to human physiology and pathology as complete as possible, to prepare a separate treatise on the subject of the crystallizations formed in the various fluids, &c, of the body, under the title of Human Crystallography.

We will now pass in review the fluids comprehended in the division of Unorganized Fluids. In reference to some of them, but little remains to be said, as will have been inferred from a knowledge of their structureless character. In the treatise on Crystallography, however, many interesting and important details will be given.

The Unorganized Fluids comprise the saliva, the bile, the sweat, the urine, and the gastric, pancreatic, and lachrymal fluids; these several fluids especially deserve the name of secretions, since they are elaborated by large and complexly organized glands.


THE SALIVA.

The saliva is a peculiar fluid secreted by the parotid, sub-maxillary and sub-lingual glands, from which it is conveyed by certain ducts into the mouth, where it becomes mingled with the buccal mucus. The amount of saliva secreted during the day is estimated at from ten to twelve ounces; during salivation, either spontaneous or induced by mercury, the quantity may exceed two or three quarts. It is worthy of remark, however, that in these latter cases the mercury has never been detected in the saliva.

Mitscherlich* made the following observations on a person having a salivary fistula, and in whom the saliva could be collected directly as it flowed from Steno's duct. He found that there was no flow of saliva while the muscles of mastication and of the tongue were in complete repose, and all nervous excitement avoided. He observed, also, that during the acts of eating and drinking, especially at the commencement, the secretion was most abundant, and in proportion to the stimulating nature of the food and the degree to which it was masticated. From two to three ounces of saliva flowed from the duct in the course of twenty- four hours.

The solid constituents of the saliva are composed of fat, ptyalin, watery and spirituous extractive matters, a little albumen, certain salts, a trace of sulphocyanogen, mucous corpuscles, epithelial scales, and, lastly, corpuscles resembling mucous globules, which have been termed salivary corpuscles, and which are probably nothing more than epithelial cells in progress of development.

The salts of human saliva are, according to Mitscherlich, chloride of calcium, lactates of soda and potash, soda, either free or combined with mucus, phosphate of lime, and silica.

In certain pathological states Simon detected in the saliva acetic acid, and a considerable quantity of a substance resembling caseine.

The saliva is with difficulty to be obtained in a pure state, it being generally intermixed with a greater or less quantity of buccal mucus ; now the normal reaction of the saliva is alkaline, that of mucus acid; it therefore follows, the fluids in question being thus intermingled in variable proportions, that the reaction presented by the fluid obtained varies according to the relative quantity of each ingredient; thus sometimes the saliva, when tested, will appear to be acid, alkaline, or neuter, and the same will be the case with the buccal mucus.


  • Rust's Magaz. vol. xl. 16


The true reaction of the saliva, then, can be ascertained only by obtaining it unmixed with the mucus of the mouth, and then testing it; this may be effected by first washing the mouth with water, and then applying the test-paper to the saliva as it flows from the orifice of its ducts.

The fact referred to of the admixture of the two fluids, saliva and mucus, will serve to explain why test-paper, applied to the upper surface of the tongue, exhibits frequently an acid reaction, while that placed beneath it manifests the presence of an alkaline fluid.

In morbid states the normal reaction of the saliva may undergo a complete change, and it may become either neuter or acid : this alteration has been especially observed to occur in deranged conditions of the stomach, in acute rheumatism, in cases of salivation, and, according to Donne\ in pleuritis, encephalitis, intermittent fevers, uterine affections, and amenorrhea.

Acid saliva doubtless exerts a very injurious effect upon the teeth.

The admixture of the saliva with mucus is readily shown by means of the microscope, which reveals the presence of mucous epithelial scales in all stages of their development; as the scales found in the sweat are derived from the desquamation of the epidermis, so are those of the saliva and mucus from that of the epithelium.

The saliva, as well as the sweat, yields on evaporation crystals of the various salts referred to in the analysis.

Blood corpuscles are sometimes present in the saliva and mucus; these proceed usually from the gums.

The uses of the saliva in the animal economy are classified by Dr. Wright as follow:

Active. — 1. To stimulate the stomach and excite it to activity by contact. 2. To aid the digestion of food by a specific action upon the food itself. 3. To neutralize any undue acidity of the stomach by supplying a proportionate alkali.

Passive. — 1. To assist the sense of taste. 2. To favour the expression of the voice. 3. To clear the mucous membrane of the mouth, and to moderate thirst.


The bile, like the unorganized fluid already described, presents but little of interest to the microscopist in its normal state.


It happens, however, occasionally, when it has been retained in the gall-bladder for a long time, in consequence of which it has become inspissated, that it does contain solid and coloured particles.

These particles have been noticed by Scherer* and also by Dr. H. Letheby of the London Hospital, who was so considerate as to transmit, for my examination, a portion of inspissated bile, containing them, as also plates of cholesterine, in great numbers.

The bodies in question consist of two parts, an external colourless investing portion, and an internal coloured and granular matter; this disposition of the colouring matter imparts to them the aspect of " pigment cells," which, in fact, Scherer considers them to be.

There are but three kinds of cells, which, if cells at all, they could be by any possibility, viz: liver, epithelial, or pigment cells. Now, they are certainly neither of the first two mentioned, as may be inferred from the dissimilarity of size, appearance, and structure with these; and they are as surely not "pigment cells," because such structures do not enter into the organization of the liver.

It is, then, conceived that these cell-like bodies are not true cells, but are to be regarded as masses of concrete mucus, enclosing more or less biliary colouring matter; the great differences observed in their form, size, and general appearance, are all opposed to the notion of their being definitely organized cells.

The meconium of infants very generally contains the cell-like bodies described, together with intestinal mucus, cuneiform epithelium, and occasionlly cholesterine in a crystalline form.

THE SWEAT.

The sudoriparous glands, distributed over the whole surface of the body, constantly secrete a very considerable quantity of watery fluid: this fluid passes off usually in the form of an insensible vapour; in some cases, however, as under high external temperature, active exercise, and in certain stages and forms of disease, it collects on the skin in the form of drops, which, in drying up, deposit their solid constituents over the whole extent of the cutaneous surface : it is then more particularly termed sweat.

Many attempts have been made to determine the amount of fluid passing off by the skin; the average quantity, according to Seguin amounts to about twenty-nine ounces of fluid, the maximum to five pounds, and the minimum to one pound, eleven ounces, and four drachms.

  • Unlersuchungen, &c, p. 103.


The amount of solid constituents carried off with the fluid is, comparatively, very small, not exceeding in the twenty-four hours seven or eight scruples ; the remainder being merely water, retaining in it -carbonic acid and nitrogen, the quantity of the former gas being increased by vegetable diet, and the amount of the latter by an animal regimen.

Simon has established the existence, in normal sweat, of —

1. Substances soluble in ether: traces of fat, sometimes including butyric acid.

2. Substances soluble in alcohol: alcohol extract, free lactic or acetic acid, chloride of sodium, lactates, and acetates of potash and soda, lactate or hydrochlorate of ammonia.

3. Substances soluble in water : water extract, phosphate of lime, and occasionally an alkaline sulphate.

4. Substances insoluble in water: desquamated epithelium, and, after the removal of the free lactic acid by alcohol, phosphate of lime with a little peroxide of iron.

The quantity of fluid exhaled is subject to very great variations; thus, it is increased by a dry and light atmosphere, while it is diminished by a damp and dense condition of the air. It is at its minimum at and immediately after meals, while it is at its maximum during the actual period of digestion. The cutaneous perspiration is in antagonism with the urinary secretion; thus, an excessive secretion of urine diminishes that of the skin, and a diminution of the activity of the kidneys is usually followed by an augmentation of that of the sudoriparous glands.

But little of interest, in a microscopic point of view, attaches to this fluid; the only solid organic constituent contained in it being detached scales of epidermis, which is ever undergoing a process of destruction and renewal; these scales, therefore, do not form part of the sweat, but become mixed up with it in a secondary manner.

The copious formation and discharge of the cutaneous fluid which occur under certain circumstances, thus do not merely afford a relief to internal organs, but serve, also, by detaching and washing away the older and useless cells, to cleanse the epidermis, and to render this more efficient as an evaporating surface.

The crystals formed on the evaporation of the sweat, in states of health and disease, have been but little studied; it is probable that a knowledge of them would lead to the discovery of some facts of interest.

The cutaneous fluid, it is known, is in health acid ; there are some situations, however, in which it is constantly alkaline, as in the axilke, about the genital organs, and between the toes ; this, probably, arises from its admixture with the secretions of the small follicles which are situated in those parts.

The sweat, like the urine, is to be regarded as a cleansing fluid, the system being through it relieved of certain surplus and effete matters.

The pathology of the sweat is but little known ; albumen has been observed in it by Anselmino, in a case of febris rheumatica, and Stark states, that it may be met with in the sweat in gastric, putrid, and hectic diseases, and also on the approach of death. The amount of acetic acid, ammonia, and the salts, may all be increased. Uric acid and quinine have been found in the sweat, the latter preparation being of course at the time administered medicinally.

THE URINE.

Few fluids have been more studied of late years by the microscopist than the urine; this has arisen from the elegance of form, variety of composition, and important character of the numerous crystalline deposits which are formed in it in states of health and disease, and which can be satisfactorily determined only by the aid of the microscope.

The great advantage of the application of the microscope over that of chemical tests to the study of the urine is, that the indications which it affords are not merely certain, but also prompt and facile, while the results obtained through the agency of chemistry, although not less certain, are often tedious and difficult.

The description of the various crystals formed in the urine is reserved for another occasion ; in this place will be noticed only the organic constituents which occur in normal and abnormal urine.

In order that the pathological alterations to which the urine is liable may be more clearly understood, it will be advisable, first, to describe the appearance and the constitution of healthy urine.

Healthy urine, when first passed, is a limpid fluid of an amber colour, emitting a peculiar odour, exhibiting an acid reaction, and having a specific gravity of about 1011.

Abandoned to itself, it soon loses its limpidity, becomes troubled, and putrefies more or less quickly, according to its chemical constitution and the state of the temperature.

The following is Berzelius' analysis of healthy urine, and with which all other subsequent analyses have been found to agree to a very considerable extent: 1000 parts contained —


Water, 933 00

Solid residue, 67 00

Urea, 30-10

Uric acid, 100


Free lactic acid, lactate of ammonia

alcohol and water extract,


1714


Mucus, 32


Sulphate of potash, 371^


Sulphate of soda, 316


Phosphate of soda, 2 94


Biphosphate of ammonia, 165


Chloride of sodium, 4-45


Chloride of ammonium, 150


Phosphate of lime and mag]lesia, 100


Silicic acid, 03>


Fixed L salts, 15 29.


It will be seen from the above analysis that healthy urine does not contain the nitrogenized principles albumen, fibrin, or caseine, which are encountered so frequently in urine voided in disease.

The only solid organized constituents which are constantly encountered in healthy urine, are mucous corpuscles and epithelial scales; these do not form part of the urine, but belong to the structure of the mucous membrane of the bladder and urethra, and both of them may be detected with the greatest facility by the microscope. On account of their greater specific gravity, they subside at the bottom of the vessel containing the urine, where they may, at most times, be procured for examination.

Occasionally, however, in the urine of man, under the circumstance already referred to in the article on the semen, the spermatozoa are present in the urine also.


PATHOLOGY OF THE URINE.


The organic principles contained in diseased urine may be divided, firstly, into those which are usually encountered in that fluid in a state of solution, but which do yet, under certain circumstances, assume the solid form ; and, secondly, into those which, being definite organisms, occur only in a solid condition. Albumen, fibrin, caseine, and fat, belong to the first, and the blood and pus corpuscles to the second division.

Albuminous Urine.

Albumen is frequently present in the urine in disease; it has been noticed to occur especially in Bright's disease of the kidney, and in the urine passed after scarlatina.

If the albumen be present in any considerable quantity, nitric acid or bichloride of mercury will cause a precipitate, and the urine will become turbid on the application of heat, and deposit flocculi of coagulated albumen.

The colour, specific gravity, and reaction of albuminous urine are various ; thus, it may be either light or dark coloured, it may be of high or low specific gravity, it may exhibit either an acid or an alkaline reaction, or it may be neutral.

When the albumen is small in quantity, heat is the most efficient test for its detection; it is only when the urine manifests a decided alkaline reaction, that nitric acid is preferable, the albumen being held in solution by the free alkalies.

Urine may, however, become turbid from the application of heat, even when no albumen is present ; this arises from precipitation of the earthy carbonates; in these instances, the addition of nitric acid will immediately disperse the cloudiness, and the reapplication of heat will not occasion any further precipitation.

Dr. G. O. Rees has observed that the urine of persons who have been taking cubebs or balsam of copaiba is rendered turbid by nitric acid, although it contains no albumen; this urine, however, is not affected by heat.

From the facts contained in the two preceding paragraphs, it follows that a precipitate might possibly ensue on the application of heat, and by the addition of nitric acid, and yet no albumen be present in the urine.

If the precipitate yielded by nitric acid, added to urine impregnated with the active principles of cubebs or copaiba, be examined with the microscope, it will be found to consist of minute oil bubbles, which are of course readily soluble in ether.


Fibrinous Urine.

Fibrin has been encountered in the urine independently of the other constituents of the blood : Zimmerman* has described seven cases of fibrinous urine.

Such urine, if the fibrin existed in it in any quantity, would coagulate or form a clot.

It is necessary in these cases not to confound mucus with fibrin ; the former, under the microscope, exhibits the well-known mucous corpuscles, while the latter appears either filamentous or simply granular.

Fatty Urine.

The urine may contain fat, either separately or conjointly with albumen, or with caseine, and probably also sugar: the urine holding fat in a free state may be called fatty ; that in combination with albumen, chylous ; and lastly, the urine in which fat occurs in connexion with caseine and sugar may be denominated milky urine.

Fatty urine has been observed to occur frequently in persons labouring under phthisis; the fat, as the liquid cools, forming a thin pellicle on its surface, the nature of which may be at once ascertained by the microscope, which, if it be really fatty, will reveal the presence of innumerable fat globules.

Cases have been recorded in which the quantity of fat has been so considerable that it could be detected with the naked eye.

Chylous Urine.

Chylous urine is a white semi-opaque fluid, and contains both fat and albumen; the former may be detected by means of the microscope, and the latter will be coagulated by heat, by nitric acid, and the bichloride of mercury. Examined microscopically, the coagulated albumen exhibits a granular texture.

This form of urine has been observed principally in cases of gout.

Milky Urine. True milky urine is of very rare occurrence, there being but two or three well-authenticated cases of it recorded; urine containing the constituents of chyle having doubtless been described, in many instances as milky urine.

  • Zur Analysis und Sunthesis der pseudoplastischen Prozesse, Berlin, 1844, p. 129.


The fat in milky urine occurs in combination with caseine, and probably with sugar also.

The fatty constituent may be detected as in the previously-decribed urines, the fatty and the chylous, by means of the microscope, and the caserne will be precipitated by the addition of a little acetic, dilute sulphuric, or hydrochloric acid, the flocculi of which, examined microscopically, will exhibit a granular, and even in many cases a globular constitution ; they will contain also a greater or less number of fat globules.

Urine containing caseine in solution may be distinguished from albuminous urine by the application of heat, which in the latter will occasion a precipitate, none being formed in the former, unless, indeed, a considerable quantity of nitric acid be also present in the urine, when a temperature of 104° Fah. will be sufficient to occasion the precipitation of the caseine.

It is not to be supposed, by the use of the term milky urine, that the milk, as such, ever exists in the urine, and that it finds its way there from the mammary gland by metastasis; the utmost that is to be inferred, from the existence of the principal elements of milk in the urine, is, that the kidney, in place of the mammary gland, has separated those elements from the blood.

Excess of Mucus in the Urine.

In catarrhus vesica, an affection to which old persons are particularly liable, mucus is secreted in considerable quantities, and is voided with the urine.

This mucus subsides to the bottom of the vessel, is semi-opaque, thick, and ropy; examined with the microscope, mucous corpuscles and epithelial scales are encountered in it.

In those cases in which the urine is very alkaline, the mucus is observed to be particularly tenacious and thready; this condition results from the action of the free alkalies contained in the urine upon the constitution of the mucus.

Blood in the Urine. Blood is frequently contained in the urine, and voided with it; thus, it is frequently encountered, in greater or less quantity, in the following cases : in inflammation of the kidneys, in injui'ies of those organs, or of the bladder itself, in cases of stricture from the introduction of a catheter, from the passage of renal or urinary calculi, and, lastly, from chronic disease of the kidneys and bladder.

The best test of the existence of the blood in the urine is the detection of the blood corpuscles by the microscope ; blood, however, may exist in the urine, and yet no corpuscles be detected, these having been dissolved by the acids of the urine. Failing, however, to detect the blood discs, if blood really be present, then the albumen, fibrin, and hematin will still remain, and may be distinguished by suitable reagents.

From the colour of urine, no conclusion can be formed as to the existence of blood in it, as urine of a deep blood-colour is sometimes met with, which on examination is found not4o contain any trace of blood.

Pus in the Urine.

It has already been stated in these pages that no absolute distinction exists between mucus and pus; and, therefore, it follows that it is in most cases impossible to determine, with any degree of certainty, whether pus exists in the urine or not.

If, however, the sediment rendered with the urine want the tenacity of vesical mucus, and contain the granular corpuscles common to mucus and pus, there is reason to suspect that the fluid in question is really purulent.

The diagnosis will, however, be greatly assisted by reference to the history and symptoms of the case ; thus, if there be rigors and hectic fever, the probability of the existence of pus will be much strengthened.

There is one circumstance which requires to be mentioned, and which greatly increases the difficulty of discrimination between mucus and pus. In some cases of purulent urinary deposits, the urine is alkaline; now, the effect of the action of alkalies on pus is to convert it into a transparent and tenacious substance in every respect resembling mucus, and which, therefore, cannot be distinguished from it.

There are but few details interesting to the microscopist connected with the Gastric, the Pancreatic, and the Lachrymal fluids; it will, therefore, be unnecessary to treat of them at any length. It is to the chemist and physiologist chiefly that the gastric fluid is interesting. They all, however, but especially the gastric and the lachrymal secretions, contain mucous corpuscles and epithelial scales, derived from the desquamation of the epithelium of the surfaces by which they are secreted, and over which they pass.


Obs. — At page 135, the opinion is attributed to Mr. Addison, that the white corpuscles of blood, mucus, and pus contain filaments; whereas it would appear, from a closer examination of the text, that the statement of that gentleman only goes to the extent of asserting, that' the fluid enclosed in those corpuscles resolves itself in its escape into the filaments, of which the fibrinous portions of blood, mucus, and pus are under certain circumstances observed to be constituted.


URINE.

[In the pathology of the urine, the microscope has now become of equal value with chemistry ; a proper consideration of this whole subject would require a volume of the size of the present one, and therefore it is not here attempted. For reference on this subject, especially on the microscopical characters of urine, the student may consult "Simon's Chemistry of Man," " Bird on Urinary Deposits ;" " Practical Manual on the Blood," by John Wm. Griffith; "On the Analysis of the Blood and Urine," by G. Owen Rees; "A Guide to the Examination of Urine," by Alfred Markwick; "Frick on Renal Diseases;" "Prout on do."

Those who wish to study the pathology of the urine, with the microscope, will find the following hints useful. After allowing the urine to stand for a little time, more or less sediment will take place. This is to be drawn up by means of a pipette, and a drop placed on a plain glass slide, and covered with thin glass. It is then ready for examination, first with a one-fourth inch object-glass, and afterward with a one-eighth. This high power is necessary to recognise the presence of blood, mucus, or pus corpuscles, or the minute crystals of oxalate of lime.

When the presence of an undue quantity of lithate of ammonia is suspected, the test-tube or other glass vessel containing the urine must be heated gently, when the supernatant fluid, with the lithate, may be poured off", or removed with a pipette. Most of the urinary sediments can be well preserved ; the most transparent, such as oxalate of lime, &c, are best mounted in fluid. For this they are prepared by being repeatedly washed in distilled water, until all trace of gummy matter, so often combined with urinary deposits, is removed. They are then placed on a plain glass slide, or in a thin glass cell, mixed with a little water by means of a pipette, and the water allowed to evaporate. A drop or two of alcohol and water, of Goadby's solution, or of the creosote-water, is to be added, and the thin glass cover applied and cemented with gold size, care being taken that no airbubbles are present.

Other urinary deposits, requiring to be rendered more transparent, are best preserved in Canada balsam. The deposit must be well washed as before, and after being placed on the glass slide, and the water allowed to evaporate, must be mounted in balsam with heat, as directed in the chapter on the Preservation of Objects. Certain deposits are best preserved in the dry way, such as uric acid, &c.

Other sediments, and these are chiefly salts, are best mounted in syrup, made thick, and mixed with a little gum. This is to be used in the same way as the balsam without heat, and the sediment deposited in the thin glass cell, or that made with asphaltum or other cement. Castor oil has been successfully used as a medium for mounting urinary deposits. In this method, no heat is necessary.]


PART II. — THE SOLIDS.

The division of the various constituents of the animal fabric into the two orders of Fluids and Solids, although a very ancient one, is yet, to a certain extent, arbitrary and artificial. The truth of this observation is rendered apparent on reference to the several fluids, the description of which has just been brought to a conclusion, and all of which contain suspended in them, either as essential or as accessory elements, various solid and organized particles : the liquid portion of some of these compound fluids exhibiting also a distinctly organized constitution; as, for example, the liquor sanguinis and the fluid parts of mucus and of pus.

The distinction referred to is not, however, without its use, and is sufficiently well founded to serve the purposes of classification.

Of the Solids themselves it is unnecessary to make any formal subdivisions : they will simply be treated of in the order of their natural relationship with each other.

Thus, the various solid structures entering into the constitution of the animal organism will be described consecutively as follows, each forming the subject of a distinct article : Fat, Epithelium, Epidermis, Pigment Cells, Nails, Hair, Cartilage, Bone, and Teeth; the various Tissues, the Cellular, under which head Ligaments and Tendons will be described, the Elastic, the Muscular, and the Nervous, including the description of the Brain and Nerves ; the Glands, Vessels, Membranes ; and, lastly, the Pathology of the Solids, will be treated of.

Article VIII. — Fat

The transition from the fluids to the solids would appear to be a very easy and natural one through the substance about to be described : thus, fat bears an evident relation to both the former and the latter, remaining during life in a soft and semi-fluid state, and after death becoming hard and solitl; it is, however, to the milk globules among the fluids that it manifests the closest affinity, the fat vesicles, especially those of early life, and the milk globules resembling each other in form, in appearance, and in the manner in which reagents act upon them.

Fat is made up of the aggregation of a number of globules or vesicles, which some deem to be true cells, and which are held in juxtaposition by intersecting bands of cellular tissue; these vesicles, have a smooth surface, semi-opaque texture, and they reflect the light in the strongest manner.

Contents. — The contents of fat vesicles usually present a homogeneous appearance; sometimes nevertheless — as when undergoing decomposition, and when they have been subjected to pressure — they exhibit a granular aspect ; these contents are of an oily nature, and chemists have detected in the lard of the pig the organic products, oleine, stearine, margaric acid, a yellow colouring matter having the odour and the nauseous taste of bile, and the chemical salts, chloride of sodium, acetate of soda, and traces of carbonate of lime and oxide of iron. It is probable that of these constituents the presence of the chloride of sodium depended on the mode of preparation of the lard.

Form. — The form presented by the fat vesicles is various, but is usually either globular, oval, or polygonal. The first shape is encountered in the fat of young animals especially (see Plate XVIII. fig. 1); the second in that of adults (see fig. 2); and the third in situations where the fat is subjected to considerable pressure, and on solidification after death. The fat vesicles of the pig are described as being elongated and kidney-shaped. This shape, however, is of rare occurrence, and cannot be regarded as the ordinary and characteristic form, which is most generally more or less spherical or oval. Raspail, observing this exceptional form, was led to institute from it an erroneous comparison between fat vesicles in general and the starch granule.

Size. — The fat vesicles of the adult are usually several times larger than the solid corpuscles of any of the fluids described — the blood, mucus, and milk; the size of the fat vesicles in any given quantity of fat is not uniform ; but, like the globules of milk, varies exceedingly, the dimensions of the larger vesicles surpassing several times those of the smaller.

One exceedingly interesting law has been observed in reference to the size of fat vesicles; thus, it has been ascertained that their average magnitude increases from infancy up to adult age : in accordance with this law, the fat cells of an infant will be found to be several times smaller than those of a full-grown person, and those of a child again of an intermediate size. This law will be apparent from an examination of the figures given. (See Plate XVIII.)

Colour. — The colour of fat is subject to considerable variations, but it usually exhibits a tinge, more or less deep, of yellow. The fat of young animals is usually of a lighter colour than that of the fullgrown and aged; this may be seen by a comparison of the fat of an infant with that of an adult, or of the fat of the calf with that of the ox; in the former it is almost white, while in the latter it frequently exhibits a deep and golden hue. The differences of colour referred to doubtless denote differences in the relative proportion of the different, constituents of fat.

In some animals, also, fat of various bright colours is encountered, especially in Birds, beneath the skin of the beak and of the feet; in the Crustaceae and in some of the Reptilia. In the Triton, the fat is of a deep orange-colour, approaching to red. The coloration of the iris of birds depends, according to Wagner, upon a fat which is accumulated in drops, and perhaps also in cells.

Consistence. — The consistence of fat is different in different animals, and also varies in accordance with the temperature; thus, the fat of the pig is softer than that of the ox or sheep; that of the human subject is intermediate between both in its consistence, and all kinds of fat are harder in cold than in warm weather. The variation in the solidity of fats depends upon the amount of stearine and oleine which they contain ; the hard fats containing a greater quantity of stearine than the soft fats, in which the oleine is greatest.

Structure. — Most observers agree in assigning to each fat vesicle a distinct investing membrane, notwithstanding which fact the proofs adduced by them of the existence of such a structure are by no means so decisive as to render such a conclusion any thing more than doubtful: thus, micrographers, hitherto, have been unable to demonstrate the presence around normal fat vesicles of an enveloping tunic, but have been contented to rest their opinion upon the indirect and uncertain evidence to be derived from a knowledge of the action of reagents ; upon testimony, in fact, analogous to that upon which Henle and Mandl decided in favour of the existence of a membrane surrounding the milk globule.

Schwann, indeed, states that he found the membrane of the fat cell to be almost as thick as the blood globule of man in an infant affected with mollities ossium*

Henle also has observed around the obscure periphery of a fat cell a strait and clear band, but could not assure himself that this was not the result of an optical illusion. f

The above are the only trustworthy observations of a direct character recorded in proof of the existence of a distinct tunic to the fat vesicle, and they are evidently not of a satisfactory or decisive nature.

The indirect testimony procured from a knowledge of the action of reagents is as follows: Ether is stated to render the contents of the fat vesicle fluid and transparent, without, at the same time, diminishing its size, as is proved by the fact that on the resolidification of its contents, the vesicle presents the same form and dimensions as at first.

Again, acetic acid, according to Henle, acts upon the fat vesicle as upon the milk globule, destroying the membrane in different places ; it permits the escape of a number of globules of oil or grease, which, like pearl-drops, remain attached to the larger vesicle.

Ether, however, produces other effects than those usually described, and which are mentioned above; thus, when applied to the fat vesicles of the pig, many of them will be seen to burst, and to collapse frequently to less than the fourth of their original size, losing, at the same time, all definite form ; and, in proportion as the vesicle collapses, one large circular drop, or two or three smaller ones, will be seen gradually to form around and envelope the shrunken vesicle, which is, however, never entirely dissolved.

There are other observers again, as Schwann and Henle, who consider that fat vesicles are not merely provided with an envelope, but that they are true cells, possessing both cell wall and nucleus.

Thus, Schwann noticed in the wall of the fat vesicles of the child already referred to, a nucleus of round or oval form, sometimes flattened, and sometimes not so.

  • Mikroskopische Untersuchungen, p. 140, f Anal. Gen. p. 422.


Furthermore, Henle writes, "very frequently the wall presents a salient point on some part of its extent, and in that position exists a nucleus, or a trace of a nucleus. Sometimes there are two nuclei, and in very many cases they cannot be observed at all."*

Again, Mandl has made the observation in examining the fat tissue of young rabbits, and especially in taking the little masses of fat which lie along the vertebral column in the interior of the pectoral cavity, that the vesicles appear but half filled, and that they consist of two parts, an inner one conveying the aspect of a drop of oil, and an outer membranous portion, f

Such are the facts hitherto recorded in favour of the presence of a nucleus in the fat vesicle: it will be seen that although they are more definite and satisfactory than those adduced in proof of the existence of an investing membrane, yet that they are scarcely in themselves sufficient to set at rest the question of its cellular nature.

The observations, then, cited above, while they fail to demonstrate sufficiently the true organization of the fat vesicle, yet render it extremely probable that it is really cellular. In favour of this view, a few additional observations have occurred to myself, which are conclusive on one of the two debated points of the organization of the fat vesicle. The first have reference to the outer membrane. If a thin slice of any of the softer fats placed between two plates of glass be pressed firmly, though not with too great violence, and subsequently be examined with the microscope, it will be seen that the vesicles have not run into each other, but still preserve their individuality.

Again, ether applied to the fat vesicle does not entirely dissolve it ; even when it causes it to burst and collapse, a residue always remains, and this probably is membranous.

Furthermore, if a thin slice of fat be placed between two plates of glass, and having been forcibly compressed, be examined with the microscope, it will be seen that some of the vesicles have burst, discharging a portion of their contents, the membrane of the fat vesicle then becoming visible, and declaring its existence by certain folds and markings, into which it falls on the escape of its contents, and by the jagged outline of the rent through which those contents passed. (See Plate XIX. jig. 2.)

Finally, decomposition produces an effect somewhat analogous to that occasioned by pressure; the fat vesicles burst, and their fluid contents escape, leaving the membrane in most cases entirely empty, and which, as well the aperture in its parietes, may be easily detected with the microscope ; the soft contents of the vesicles break up, and resolve themselves into globules of an oil-like appearance. (See Plate XIX. fig. 4.)

  • Anal. Gen. p. 422. f Anaiomie Microscopique, p. 141.



The second set of observations relate to the nucleus. If a thin slice of the fat of the pig be pressed as before between two slips of glass with a moderate degree of pressure, and then be submitted to the microscope, in very many of the cells will be seen a dark nucleus-like body- This experiment will not, however, always succeed. (See Plate XIX. j%. 1.)

A body of a similar description, but of a more defined form, is very frequently encountered in the decomposing cells of marrow fat; this nucleated condition of the cells preceding their rupture. (See Plate XIX. fig. 3.)

Again, in some fat cells contained in a small encysted tumour removed from over the nasal bones, and kindly sent, to me for examination by W. H. Ransom, Esq., of University College Hospital, (to whose zeal and intelligence I am indebted for many interesting specimens of morbid structure,) nucleoid bodies were distinctly visible even without pressure, although they became more apparent after a gentle degree of compression had been applied. (See Plate XIX. fig. 6.) The apparent nuclei in the cases related differed from each other somewhat, being more defined and darker in the two latter than in the former; the cells themselves too were not identical in appearance ; thus, the margins of those of the pig and of the human marrow fat were smooth and distinctly defined, while those from the tumour were less regular and distinct. (See Plate XIX. figs. 1 . 3. 6.) Now these nucleus-like bodies in the several cases mentioned, although occupying the position of nuclei and presenting the appearance of such, it is very possible were not in reality true nuclei; it seems to me that their formation might be accounted for without any reference to a nucleus. Thus with respect to the nucleod bodies in the cells of the pig produced by pressure, their formation might be explained as follows : the mutual compression of the fat vesicles upon each other would tend to occasion a condensation of the semi-fluid contents in the centre of each, and in this way the appearance of nuclei would be produced.

Again, the semblance of a nucleus in the decomposing cells might be supposed to depend upon the partial escape by endosmosis of the contents of those cells, the portion remaining in them representing a nucleus merely from the position occupied by it in the centre of the cells.

The formation of the nucleated bodies in the third case would seem to point to and to require a different explanation. Decomposing fat frequently exhibits a crystalline arrangement; now, it is conceived that the outer part of each vesicle had become softened and broken down, in consequence of commencing decomposition or of disease, preparatory to its assuming the crystalline form, the central part at the same time remaining unaffected.

It will be seen that the preceding observations, in relation to the presence of a nucleus in fat vesicles, are not decisive, although they add weight to those of anterior observers, and render it still more probable that they are really nucleated cells.

The facts adduced, however, in reference to the existence of an investing membrane are quite conclusive.

On the vesicles of decomposing human fat, it is a common occurrence to meet with stelliform figures, each being composed of a number of delicate striae radiating from a central point. On the smaller vesicles but a single figure of this description will usually be met with, but on the larger there may be three or four. When but one is present, it usually covers about a third of the surface of each vesicle. (See Plate XIX. fig. 5.)

Henle* observes of these that they might be metamorphoses of the nuclei of the cells; "nevertheless," he says, "they have more analogy with crystalline deposits."

The occurrence of two, three, or four of these on the same cell is opposed to the idea of their connexion with the nuclei; and the observation of Mandl, who noticed their formation on butter, is conclusive on this point.f

Vogel,J as also Gerber,§ regard the figures in question as groups of crystals of margaric acid.

Distribution. — The fat vesicles are distributed in groups, which lie near to and follow the course of the blood-vessels. (See Plate XVIII. fig. 1.) This arrangement is particularly evident in the mesentery and omentum, and may be compared to that of a bunch of grapes, the fat vesicles representing the grapes, and the vessels the stalks of the bunch: in one particular only does the comparison fail; thus, each grape of the bunch receives and is attached to a separate pedicle, which is not the case with the fat vesicles, although one observer has asserted that a separate vessel is distributed to each vesicle. The groups of fat vesicles occurring in young animals, in which each globule is circular, may be compared to heaps of shot piled up upon each other.


  • Loc. cit. p. 423. f Anat. Mia, f. 143.

% Arileilung zum Gebrauche des Mickroskops, p. 289. tab. 111. fig. 2.

§ Gerber's General Anatomy, translated by Gulliver.


In those situations in which the fat occurs in thick and dense masses, the arrangement referred to is- somewhat different. The fat vesicles are still parcelled out into groups by means of intersecting cellular bands ; but the several groups lie in close contiguity, instead of being, as in the former case, separated from each other by distinct intervals. Thi'oughout these masses, too, but few blood-vessels are distributed.

The intimate arrangement of the fat vesicles having been thus briefly sketched, it remains to describe the general distribution of fat throughout the body.

In man, fat is developed principally in the loose cellular tissue ; it is encountered forming a layer of variable thickness in that which is situated immediately beneath the skin; in the serous membranes, as in the omenta, the mesenteries, and the epiploa; on the surface of the heart, and around the kidney.

In certain situations the sub-cutaneous fatty layer experiences an increased development designed to fulfil certain peculiar intentions; thus, in the soles of the feet, the palms of the hands, in the female breast, in the region of the pubis, and over the glutei muscles, especially over those of the Hottentot women, fat is developed usually in considerable quantities.

This superficial layer of fat is also generally thicker in children and in women than in men.

Again, there are other peculiar situations in which fat is almost invariably encountered, as in the orbit, in the articulations, where it constitutes the glands of Havers, in the shafts of the long bones forming the marrow, in the vertebral canal, and in many other localities where vacancies occur which require to be filled up. The marrow differs only from ordinary fat in that the cells composing it are more circular, with but little admixture of cellular tissue.

On the other hand, there are situations in which, under no circumstances, is fat developed, as in the eyelids, in the axillae, between overlapping muscles, and in the genital organs.

Quantity. — The amount of fat varies greatly in different species of mammalia, in different individuals of the same species, and in the same animal at different times.

Thus, certain animals seem to have a peculiar aptitude for the formation of fat, as the pig.

Again, the various members of one family are sometimes observed to be remarkable for the constitutional predisposition exhibited to the formation of fat. Again, other families are met with equally remarkable for their indisposition to fatten.

Lastly, in some animals the fat accumulates at particular periods in greatly increased quantities, as in the hibernating mammalia, and in the. larvae of insects. In man the fat usually undergoes an augmentation after the meridian of life has been passed.

Castration peculiarly predisposes the system to the formation of fat.

Occasionally, also, fat is secreted in vast and abnormal quantities : where this augmentation is general, it constitutes the diseased condition of obesity; and where it is only partial, it gives rise to tumours, often of great magnitude.

In general, a certain degree of fatness argues a healthy and vigorous condition of the system, while its excess or inordinate accumulation denotes either a degree of weakness of constitution or a peculiar and unexplained state of the system.

Disappearance. — Of all the solids in the body, fat is developed and destroyed with the greatest rapidity: in illness, it disappears with surprising quickness, and is formed again, under the influence of recovery, with almost equal celerity.

The exact changes which occur during the disappearance of fat are unknown; whatever they may be, they doubtless affect each individual fat vesicle throughout the body, and their nature being ascertained in a single cell would serve to explain the disappearance of fat over the entire body. It is uncertain whether the contents of the vesicle disappear, the membrane remaining, or whether both are effaced together. Beclard says that the fat vesicles themselves disappear.* Hunter, on the contrary, assures us that they may be distinguished even when they are empty. f Gurlt states that they contain serosity in place of grease in lean animals. J

The immediate cause of the disappearance of fat most probably depends upon interrupted nutrition ; the contents of the cells escaping through their walls become absorbed by the lymphatics, and thus removed into the circulation. This view is supported by the observation of Henle, who states that, after repeated losses of blood, the quantity of grease in the blood augments considerably, on the surface of which it is often seen swimming as a cream or pellicle.


  • Analomie Generate, p. 163.

f "Remarks on the Cellular Membrane," in Med. Obs. and Inq., vol. ii., Lon., 1757.

I Physiologie, p. 20.


Uses. — The uses of fat are manifold and important.

1st. It serves to impart softness to the texture of the skin.

2d. It adds grace and symmetry to the outlines of the body.

3d. In certain situations, as in the soles of the feet, in the palms of the hands, and over the glutei muscles, it serves as a protection against the effects of pressure.

4th. Being a bad conductor of caloric, it prevents the too rapid dissipation of the heat generated in the system.

5th. It is to be regarded as a reserve store of nourishment set apart by the system during the period of its health and strength, and designed to meet certain exigencies, when the inhei'ent powers of the constitution are called into requisition, as in times of hunger and sickness.

Distinctive Characters of Oil Globules. — The contents of fat vesicles are, as already stated, of an oleaginous nature, which, when they escape from the vesicles, assume the form of oil drops; these are often met with in the various fluids and solids of the system apart from the fat vesicles, from which it is necessary that they should be discriminated. There are several characters by which oil globules may be distinguished from true fat vesicles; thus, they are of a fluid nature, are usually perfectly spherical, and, on account of their fluidity, in place of being globular, are generally flat; they are seen sometimes to alter their shape, as when they roll over on the surface of the object-glass, or come in contact with obstacles; they reflect the light less powerfully, and, lastly, the slightest degree of pressure causes them to coalesce.

There is but little probability of confounding oil globules with air bubbles ; these have a different colour, reflect the light differently, and are perfectly globular.

See Appendix, page 538.


PAT.


[No farther hints are necessary on the preparation of fat for examination, or the use of reagents while under examination, than those given in the text. In order to display the blood-vessels of the fat vesicles, their injection is necessary. These vessels are represented in Plate LXX., fig. 3, and their existence is referred to in the Appendix, page 538.

These vesicles can only be injected when the injecting material is very fine, and the operation is perfectly successful. In those instances in which the papillae of the skin are well injected, the fat vesicles will also be found more or less completely injected ; the injection must be made from the main vessel, usually the vein, that supplies the part.]


Article IX. — Epithelium

As the external surface of the body is invested with a cuticle which has received the name of Epidermis, so are its internal free surfaces in like manner clothed with a delicate pellicle which has been denominated Epithelium.

Both the epidermis and epithelium are constituted of cells : there is this difference, however, between them, that while the former, by the intimate union and super-imposition of its cells, exists as a distinct and continuous membrane, the latter, owing to the feeble cohesion of its constituent cells, can scarcely, except in certain situations, be shown to exist as a united and extended structure.*

The epidermis and epithelium are, therefore, hardly to be regarded as distinct structures, but rather as the same, the differences observed between them being merely modifications, the result of the different circumstances to which they are each subject.

The essential identity of the two may be shown by an examination of the epidermis at the outlets and inlets of the body, where, by gradual transition, it may be traced inwards into the condition of epithelium; and this, also, traced from within outwards, will be observed gradually to acquire the characters of epidermis; so that, within a certain distance of the termination of the cavities of the body, which open externally, the epithelium may also be demonstrated as a distinct membrane; this membrane may be followed in man from the lips as far backwards as the posterior part of the mouth, also passing over the tongue; and in the horse and in birds it may be shown to exist in the stomach and gizzard.

The epithelium will be first described, inasmuch as its organization would appear to be more simple than that of the epidermis, which, by modifications of its cells, is converted into so many apparently distinct structures.

It has been remarked that the internal free surfaces of the body are covered by epithelium: these surfaces comprise those of both the open and the closed cavities, the former of which include the alimentary canal from mouth to anus, the genito-urinary organs and passages of both the male and female, and the respiratory track, consisting of the trachea, bronchi, cells of the lungs, and nares; the latter consist of the great serous sacs of the head, chest, and abdomen, and the lesser ones of the pericardium, tunica vaginalis, the cavities of the joints, and of the lymphatic and blood vessels, including the heart.


  • Leeuwenhoek first discovered in the mucus of the vagina little scales, which he

presumed formed the internal membrane of that canal, and from which he conceived they become detached by coitus. (Opera,t. i. p. 153. 155.) He likewise noticed that the mucus of the mouth contained scales, (Ibid. t. hi. p. 51,) and he saw also the cylindrical epithelial cells of the intestinal cavity. (Ibid. p. 54. 61.)


The bursas are said by Henle* not to be furnished with an investing epithelium — a statement to be received with some degree of hesitation.

It would appear, therefore, that, with the single doubtful exception alluded to, every free surface of the body is invested with its own appropriate epithelium, the ventricles of the brain even being lined with an epithelium proper to them, and the surface of the cornea being covered with one also. The existence of an epithelium in this latter situation may be directly proved by means of the microscope : and it may be inferred from the observation of the fact, that in the general casting of the epiderm of snakes and other reptiles, a delicate film is likewise thrown off from the surface of the cornea.

The epithelium has not the same character in the different situations in which it is encountered, but the cells of which it is composed differ in form and size, according to age and the locality occupied by it.

The several varieties of epithelium may be reduced into two principal types, in the first of which the cells are more or less circular or polygonal, and in the. second are elongated and conoid. These two forms may be distinguished by the appellations of Tessellated or Pavement Epithelium, and Cylindrical or Conoidal Epithelium. (See Plate XX. figs. 1 and 2.)

The Conoidal Epithelium admits of sub-division into Naked Conoidal Epithelium and Ciliated Conoidal Epithelium.

TESSELATED EPITHELIUM.

Form. — The cells of this description of epithelium form many layers, are flattened, and either circular, polygonal, or irregular in outline: the younger cells are mostly of the first shape, and are thicker than the older ones, which are irregular in form, thin and membranaceous, while the polygonal cells are encountered more particularly in certain situations, as on the choroid plexus, pericardium, and serous membranes in general. The polygonal shape is produced by the mutual compression exerted by the cells upon each other, and consequent adaptation.


  • Anal. Gen. vol. vi. p. 225.


Size. — The size of the cells of pavement epithelium varies both according to age and locality; the younger and deeper seated cells are of course smaller than the older and more superficial ones; the larger cells are met with in those situations where the epithelium is continuous with the epidermis, as in the mouth and oesophagus, the vagina, urethra, and bladder, the commencement of the rectum, the inferior division of the nares, lining the eyelids, and covering the cornea. (See Plate XX. Jig. 1.) On the contrary, the epithelium of the pericardium, ventricles, aorta, and of most of the closed cavities, is composed of cells which are very much smaller in size than those of the localities previously enumerated. (See Plate XXII.)

Structure. — Epithelial cells illustrate faithfully the doctrine of cell development, each consisting of a nucleus, cell wall, and intervening space enclosing fluid, both the nucleus and the cell wall exhibiting a granular composition.

It has been observed, that the younger cells are thicker than the older and fully developed ones, which become reduced to mere membranous expansions, from which it follows that the space intervening between the nucleus and cell wall is greatest in the younger cells, while it is almost obliterated in the older. The smaller cells are also more granular than the larger : now, these two facts stand in close relationship with the function discharged by these cells, and which is so much the more active as the cavity is large and the granules numerous.

The nucleus is likewise best seen in the younger cells: in the older ones it becomes either entirely obliterated, or it escapes from the cavity of the cell, the position which it previously occupied in it being indicated by a depression; it is for the most part circular; but occasionally, and particularly in certain localities, it is found to be oval, as in the epithelium of the lower two-thirds of the uterus, in that of the pericardium, and also in that of the blood-vessels, the aorta excepted ; it sometimes occupies a central position in each cell ; at others it is eccentric.

The properties of pavement epithelial cells, as well as their form, size and granular texture, alter also with age : thus the younger cells are dissolved, with the exception of the nucleus, by acetic acid, while the same reagent applied to the older ones produces scarcely any appreciable effect.

Epithelial cells, on the addition of water, or after death, become white and opaque — a common effect of water on all animal structures. The change in the case of the epithelial cells probably depends upon the coagulation of their fluid contents; and to it the characteristic dulness of the eye after death is due.

Distribution. — This form of epithelium is more extensively distributed than the conoidal variety: it is encountered on the free and serous surfaces of all the closed cavities, as of the cranium, thorax and pericardium, abdomen and tunica vaginalis, lining the lymphatic and blood vessels; even the ventricles of the brain itself, in which it rests immediately upon the cerebral substance, are not free from it: it is met with likewise near the terminations of those cavities which open externally, as in the mouth, where it extends as far backwards as the cardiac extremity of the stomach, in the lower portions of the nares, whence it passes into the frontal sinuses, in the vagina and uterus, the lower two-thirds of which it lines, as also the urethra. In the male subject it passes over the glans penis, and then enters the urethra.

The epithelium of the urinary apparatus should perhaps be referred to the pavement epithelium : its cells, however, vary very considerably in form: thus, many of them decidedly resemble the variety of epithelium under discussion ; others, however, are clavate, the narrow or fixed extremity being often produced into a long thread or filament; and again, others imperfectly represent the conoidal variety of epithelium; these last, as well as the clavate cells, are met with in the greatest quantity in the upper part of the bladder, and in the ureters.

CONOIDAL EPITHELIUM.

Form and Size. — The cells of this form of epithelium are much more regular in size and shape than those of the tesselated or pavement kind : the term cylindrical usually applied to them is, however, far from accurate, since they do not possess, even in a slight degree, the outward form of a cylinder : the word conoidal, here used, serves to express much more closely the real form of the cells of this variety of epithelium, although it fails to give an exact idea of their shape: thus, the cells in question are not merely conical with flat summits, but each cone is flattened at the sides, so that when the bases of the cones are seen directly, they exhibit the appearances of ordinary polygonal tesselated epithelium; the side view of the cells will at once make manifest their distinctness. (See Plate XX. Jig. 2.)

Conoidal epithelial cells are usually disposed more or less vertically to the surface upon which they rest, their narrow extremities being turned downwards, and attached to that surface, and the broader and free ends being directed upwards.

Structure. — The cells of conoidal epithelium have precisely the same structure as those of the previously described kind; that is, they consist of nucleus, cell wall, granules, and fluid contents: the chief difference is one of form and not of structure.

The nucleus is almost invariably oval, the long axis corresponding with that of the cell itself: it is often so large as to occasion the cell to assume a ventricose form, it being contracted immediately above and below the part in which the nucleus is situated. Some observers speak of two nuclei in a single cell: this, however, must be an exceedingly rare occurrence, as I have never yet met with a single example of the kind.

The conoidal epithelium is, as already remarked, divisible into two kinds.

Naked Conoidal Epithelium.

Distribution. — This sub-division of epithelium, to which the description just given more immediately applies, is met with investing the mucous membrane of the alimentary canal, extending from the cardiac extremity of the stomach to within two or three inches of the rectum; it is encountered likewise lining the several ducts and prolongations which communicate with this: thus, this form of epithelium exists in the gall-bladder, where it is of a deep yellow colour, in the ductus communis choledocus, in the pancreatic duct, and in the mucous crypts or follicles imbedded in the mucous membrane; It is found also in the upper portion of the nares, in the salivary ducts, in the appendix vermiformis, and in modified form in the vas deferens.

In the stomach, the naked conoidal epithelium does not exist in an unmixed form ; it occurs intermixed with pavement epithelial cells, probably derived from the oesophagus, and carried down during deglutition.

It is in the gall-bladder, the small intestines and the appendix vermiformis, that the naked conoidal epithelium exists in the greatest perfection,

Ciliated Conoidal Epithelium.

The cells of this variety of conoidal epithelium agree precisely in form, size, and arrangement with those of the first described subdivision, the only difference being, that they are possessed of the singular addition of vibratile cilia.* (See Plate XXI. jig. 3.)

The cilia taper from base to apex, and are attached to the thickened margins of the summits of the cells, ten or twelve of them belonging to each. In the frog they would appear to be not merely attached to a circular line, but also to the segment of the cell described within this. (See Plate XXI. jig. 1.)

During life, the cilia are in a constant state of activity: the power by which their motions are effected is, however, involved in the greatest obscurity: it can scarcely be the result of muscular structure, as some have supposed, since the entire cilium is many times smaller than the smallest muscular fibre. The idea has been put forth that the cilia are hollow; that they communicate with a vessel which runs along their bases, containing fluid ; and that they are moved by the successive injection and expulsion of this fluid.

One fact has been observed, which affords countenance to the above explanation of the motion of the cilia, viz : that this takes place in a determined direction : commencing in the cilia on one side, it runs along them to the opposite, the several cilia being thus successively called into action. It is this peculiar character of the motion of the cilia which has led to its comparison with the waving of a corn-field over which the wind passes in successive gusts. The motion, in whatever way effected, is singularly beautiful, and, strange to say, exhibits many of the characters of volition : thus, it will sometimes cease altogether for a time, and then suddenly commence again. It is also sufficiently powerful to effect the entire displacement of the cell or corpuscle to which the cilia are attached, and many of which may frequently be seen moving freely and quickly about, usually in circles, in the field of the microscope. This curious spectacle is most readily witnessed in the ciliary cells of the trachea of the frog, which are of a different form from those of the mammalia, being rounded in place of elongated and conoidal. (See Plate XXI. jig. 1.)

The combined motion of the cilia is also capable of putting in movement either fluids or solid particles which may come into contact with them. This fact those who are given to microscopic investigation will have had many opportunities of verifying, and one may easily at any time acquire the proof of it by mixing with the fluid in which the cilia are acting some fine powder, as, for example, of carbon.


  • To Purkinje and Valentin especially belong the honour of making known in all

its extent the phenomenon of ciliary motion, and which before that time had been observed only in some few of the lower animals, and concerning the nature of which many errors prevailed. They discovered it in the respiratory and female genital organs in 1834. (Mailer, Archiv. 1834, p. 391.)



The motion of the cilia, when acting in combination, is stated to take place always in a determined direction from within outwards. It would appear, however, from the observations of Purkinje and Valentin* that the direction is capable of reversion : thus, these observers saw the accessory branchiae of the anodon vibrate during from six to seven minutes in one direction, and afterwards, during the same lapse of time, in an opposite.

The influence of physical and chemical reagents upon the vibratile movement has been carefully examined. Thus, if a portion of vibratile epithelium be touched or scraped, the motions of the cilia will become more active, and sometimes commence again even after they had become extinct. They cease at a temperature below the freezing point, and at a degree of heat sufficient to occasion the coagulation of the animal fluids. Galvanism destroys their action, but in a local manner — a fact which a reference to the constitution of epithelium by the union of separate cells may serve to explain. Among chemical reagents, narcotics are without influence; acetic and the mineral acids destroy the motion, as also caustic ammonia, nitrates of potash and of silver. The serum of the blood prolongs its duration. Urine and white of egg are without effect upon it. Bile instantly destroys the activity of the cilia.

The ciliary motion soon ceases after death in the mammalia, but continues in many of the invertebrata, and especially in several of the mollusca, as, for example, in the river muscle and the oyster, for days after the death of the animal.

It would appear, therefore, that each ciliated corpuscle bears the closest possible resemblance to many of the infusory animalcules, and it is questionable whether its claim to be regarded as a distinct entity be not equally strong.

Distribution. — Ciliated epithelium has not been as yet discovered among the mammalia in any closed cavity, but always in situations which communicate with the air; thus, it is met with, as is generally known, lining the trachea and bronchi, extending even to their minutest ramifications ; again, it is encountered in the Fallopian tubes, and lining the upper third of the cavity of the uterus of adult animals, but not that of young mammalia. There is yet another locality in which I believe it also to exist, viz: in the convolutions of the tubuli serniniferi of the epididymis.


  • Motus Vibrat., p. 67.


On the other hand, there are many situations in which it has been repeatedly asserted to exist, but in which patient and repeated investigation has failed to reveal its presence; as, for example, in the ventricles of the brain,* covering the pia mater, and lining the eyelids and frontal sinuses.

The epithelium of these several parts, on the contrary, is pavement and not ciliated epithelium. (See Plate XXIV.)

Purkinje,J in describing the epithelium of the ventricles, does so most circumstantially, and states that he followed the vibratile movement in the sheep from the lateral ventricles through the third ventricle, and by the aqueduct of Sylvius into the fourth.

Valentin § confirms the accuracy of this description as regards man.

We find Henle|| describing the epithelium of the ventricles as a cuneiform ciliated epithelium; and in Gerber's General Anatomy, we remark that it is stated to be a tesselated ciliated epithelium. It is singular how so great an error could have originated, and still more so how it could have been so long perpetuated.

DEVELOPMENT AND MULTIPLICATION OF EPITHELIUM.

Each epithelial cell is first detected as a nucleus without any appearance of cell wall around it: this, however, may exist, closely embracing the nucleus, even from the earliest period at which this can be observed. After a time, however, a transparent border becomes visible, surrounding the nucleus: the width of this goes on gradually increasing, until at length the full dimensions of the cell have been attained: now, the outer limit of this border doubtless indicates the cell wall, the clear space between it and the nucleus being in the younger epithelial cells filled with fluid. In the conical epithelium the cell wall is not developed equally around the nucleus as in the pavement epithelium, but chiefly in two opposite directions.

It has been observed, that young epithelial cells are thicker and rounder than the older ones ; it has also been remarked, that they are more granular; facts which stand in close relation with their functional activity.


  • Purkinje in Miiller, Archiv. 1836, p. 289.

f Henle, Anat. Gen. t. vi. p. 252. \ Miiller, Archiv. 1836.

\ Repertorium, 1831, p. 158. 278. || Anat. Gen. tvi. p. 253.


It has been noticed likewise, that the nucleus in the progress of development becomes either obliterated, or that it escapes from the cell. Now, it has struck me that this disappearance of the granular nucleus and granules of the cell wall might possibly be connected with the reproduction or multiplication of epithelial cells, as well as of cells occurring elsewhere than in the epithelium, and that each granule might in reality be an epithelial cell in embryo. This is of course but a conjecture: it is one, however, which would appear not to be contradicted by any other known fact, and to have analogy in its favour; the mode of reproduction among the lower algee being precisely similar.

The occurrence of two nuclei in the same cell has been recorded by some observers, and who have from this fact drawn the inference, that epithelial cells are multiplied by division. This method of increase cannot, however, be presumed to prevail to any extent, since it is a circumstance of extreme rarity to meet with two nuclei in the same cell.

NUTRITION OF EPITHELIUM.

The epithelium has no immediate or structural connexion with the parts which lie immediately beneath it, neither does it receive bloodvessels and nerves from those parts ; it is simply dependent upon them for the supply of nourishment, of which it is the recipient, and which is derived from the blood-vessels distributed throughout the tissue of the true skin lying beneath it, and from which vessels the plasma is continually escaping by transudation or exosmosis.

DESTRUCTION AND RENEWAL OF EPITHELIUM.

The epithelium in every part of the body is continually undergoing a process of destruction, and consequent renewal.

It is less easy to establish the fact of the destruction of the epithelium in the closed cavities than in the open; nevertheless, that it really does take place even in these, may be inferred from the observation of the fact that the cells of epithelium encountered in such localities represent every degree of development, many of the older ones also being destitute of nuclei, and more or less broken into fragments. It is probable, however, that the process of destruction is slower in the closed than in the open cavities.

In the open cavities, the destruction of epithelium is doubtless more considerable and more rapid; it is also more easy to determine in these; thus, during mastication, deglutition, and digestion, a considerable amount of epithelium becomes disturbed, removed from the surface to which it was attached, and mixed up with the saliva, mucus, gastric fluid, food, &c, and finally is discharged from the system with the faeces, in which, by microscopic examination, it may readily be detected.

The fact of the gradual and continual destruction of epithelium may likewise be ascertained by an examination of the several fluids discharged from the system, as the saliva, the mucus, from either mouth, nose, lungs, urine, seminal or menstrual fluids, in all of which the microscope will reveal an abundance of epithelial cells.

The same fact may also be determined by a microscopic examination of the scum which collects during the night on the lips and around the base of the teeth of many persons.

In certain situations the epithelium undergoes not merely a gradual, but also a periodical destruction, as in the uterus at the monthly periods and after parturition.

The continual destruction of epithelium having been thus rendered manifest, its renewal follows as a matter of necessity.

In irritation of the mucous membrane of the bronchi, nose, and alimentary canal, it is possible that the epithelium, during the period of the continuance of the irritation, is entirely destroyed.

USES OF EPITHELIUM.

  • The first use of the epithelium is a passive one, it serving like the

epidermis as a protection to the more delicate parts which lie immediately beneath it.

The second use is active, the epithelium doubtless being an important agent in secretion.

Each epithelial cell may be regarded as a gland reduced to its most simple type or condition, it embodying all that is essential in the largest and most complex secreting organ, viz: the true secreting structure.

The nature of the fluid secreted by epithelial cells is not every where identical, but varies according to their exact structure and the locality in which they are found : thus, in some situations, they secrete serum, as in the serous sacs : in others mucus, as in the mouth, nose, alimentary canal, &c; in others synovia, as in the joints; in the stomach and in the duodenum, they assist in the elaboration of the fluids which are there found.

That the epithelial cells are the real agents engaged in the production of the several fluids named, is rendered certain by the facts that they correspond precisely with the undoubted secreting structure of true glands; and further, that in the situations where they are found, no other organization exists to which the function of secretion could with any degree of probability be assigned. • The importance of the office discharged by the epithelium explains, then, the universality of its distribution.

The diffusion of epithelial or secreting cells over the surface of membranes which require to be kept continually moistened by a suitable fluid, affords a beautiful example of the wise adaptation of means to an end: by no other means than that employed could the end in view be so surely accomplished, or with so great an economy of space.

The above-described uses of epithelium are common to it wherever encountered: the third use is mechanical, and accomplished only by the ciliated form of epithelium.

It has already been observed that the force of the combined action of the cilia is so great as to enable them to carry along with or drive before them fluids, and even solid particles which may happen to come in contact with them : it has likewise been remarked that the direction of their united action is invariably from within, outwards or towards the outlets of the body; at least it is so among the mammalia. From a knowledge of these facts it is not difficult to suggest the probable use of vibratile epithelium in the localities in which it has hitherto been discovered in man and the mammalia.

Thus in the bronchi and trachea, it may be presumed to be designed to facilitate the escape from those passages of any foreign particles which may have found entrance to them.

Again, in the Fallopian tubes and upper portion of the uterus, it can scarcely be questioned, but that its use is to hasten the progress of the ovum from the ovary to the uterus; and, presuming that the direction of the action of the cilia may be, and is sometimes reversed, the vibratile epithelium of these parts may be further intended to ensure the more speedy transmission of the seminal fluid along the Fallopian tubes to the ovary, upon which it has been detected by more than one observer.


EPITHELIUM.


Microscopic examination has revealed . the fact that many tumours supposed to be cancerous, especially certain tumours about the lips, were composed of degenerated epithelium. Ecker* has described these tumours of the lip, and denominated them bastard cancer of the lip. It is now ascertained that these tumours are not confined to the skin, but occur in the mucous membranes. Rokitansky has found them on the lining membrane of the larynx, trachea, stomach, intestines, and bladder. They may be also met with on the dorsal aspect of the hand, on the cheeks, scrotum, prepuce, and it may be the chimney-sweep's cancer is but an epithelial tumour. Lebert regards them as benign, since they contain no cancer-cell. Rokitansky and Bruck consider them malignant. Dr. Gorup Bezanes regards the important question to be, not whether these tumours may be benign, but whether they are altogether exempt from malignity: his observations confirm the opinion of their malignity.

See Archiv. Gen. de Med. torn xxm. p. 76, Mai, 1850.

See also Dublin Quart. Jour. August, 1850, p. 255.

PREPARATION.

The text has already indicated the different localities from which the various forms of epithelium may be obtained.

The pavement or scaly epithelium may be best studied by scraping any of the serous membranes gently with a knife, and examining the particles removed. Many of the cells after removal will be found to adhere together. The addition of a little weak ascetic acid will render the angles of the scales more apparent.

The conoldal variety of epithelium is easily obtained by macerating any of the mucous membranes, as, for instance, a portion of the alimentary canal. By this process, the epithelium becomes detached, and may be collected and viewed with the microscope. The ciliated variety possesses most interest. The cilia may be seen in motion by taking a small piece of the mantle of an oyster or mussel, folding it upon itself, and placing it under the microscope so as to allow the cilia to project. The edge of the beard will also show the cilia in motion. The fragment should be moistened with water, and covered with thin glass; a power of about 250 diameters is necessary for good observation. The currents caused in the water by the cilia in motion may be readily detected by the suspension of fine particles of carmine or charcoal in the water. These particles are first seen attracted by the ciliary motion, and then repelled.

  • Archiv. fur Physiol Heilkunde, 1849.


In quadrupeds the ciliary motion may be observed by taking a small portion of ciliated mucous membrane from an animal recently killed, and folding it in the manner already indicated^

In man the cilia may be seen in motion in recently detached nasal polypi. They may also sometimes be discovered in mucous discharges.

The ciliary motion may be studied on a larger scale in many of the freshwater infusoria, so abundant during the summer and fall months in small ponds and stagnant pools.

Epithelial cells may be preserved in the flat or thin glass cell, suspended in a weak solution of chromic acid, or Goadby's B-solution.]


Article X. — Epidermis

The entire of the external surface of the body is invested with a membrane which has been denominated epidermis, formed of superimposed layers of nucleated cells (see Plate XXIV. fig. 3), and the number of which layers is greatest in those situations in which the membrane is subject to the most pressure, as in the palms of the hands and soles of the feet, in which the epidermis sometimes attains the thickness of the T V, or even the \ of an inch.*

The form, structure, and development of the cells composing the epidermis are in every respect identical with those of the tesselated variety of epithelium already described; thus, first, the younger and deeper-seated cells are spherical in outline, and almost globular, while the older and more superficial cells become irregular in form, expanded, thin, and membranaceous ; secondly, like those of the tesselated epithelium, the cells consist of a nucleus, cell-wall, cavity, and granules; it is, however, worthy of remark, that the nucleus, as well as the majority of the granules contained in the epidermic cells, disappear at an earlier period of development than do those of the epithelium — facts which will be explained when the uses of the epidermis come to be treated of; thirdly, the plan of development is the same in the two cases, the cell-wall being developed around the nucleus, which is the part first formed.

Thus far, then, there is a close correspondence between the epidermis and epithelium ; so close, indeed, as to make it apparent that the two are but modifications of one and the same structure. The chief respects in which it diners from the epithelium are in the compact and firm union of the cells with each other, whereby it forms a distinct and continuous membrane, and in the paucity of granules dispersed throughout the cells.

The epidermis also stands in precisely the same relation with the parts beneath it as the epithelium; thus, it has no structural connexion with those parts, and receives neither blood-vessels nor nerves from them, but is simply dependent upon them for the plasma which is continually escaping from the blood-vessels of the true skin. This want of structural connexion is shown by the fact that a portion of the cuticle may be detached without its removal occasioning either pain or hsemorrhage.

  • Leeuwenhoek first observed that the epidermis was composed of scales placed

one against the other, and also that, after a certain lapse of time, they were cast off, and their place supplied by others.



This separation of the epidermis from the dermis frequently takes place during life, as from a burn, scald, or blister, or from the effusion of serum, the result, not of injury, but of disease. After death, and on the commencement of decomposition, the epidermis may be detached in large masses, the prolongations sent down to the sebaceous and sudoriferous glands also coming away with it.

The epidermis does not merely cover the whole external surface of the body, but sends processes into its various outlets, as the mouth, nose, rectum, vagina, and male urethra ; these prolongations soon lose, however, the characters of epidermis, and acquire those of epithelium.

The epidermis likewise sends down processes into the sebaceous and sweat glands, and which, forming a perfect tube, serve to convey the secretions of those glands to the surface, on which they open as raised and rounded papillae, with central depressions and apertures. (See Plate XXIII. figs. 1 and 2.)

A sheath of epidermis likewise encircles the base of each hair.

The number of these infundibuliform processes and salient papillae which open on the surface is immense, and may be stated at about 3,000 to the square inch, which, computing the number of square inches of surface in a man of average size at 2,500, would give 7,500,000 for the entire surface of the body.

In addition to the papillae, we observe on the surface of the epidermis a great number of lines or furrows which map it out into a network of small polygonal and lozenge-shaped spaces ; these are of two kinds, the one large and coarse, and corresponding with the flexures of the joints; the others smaller, occupying the interspaces between the larger, and also being generally distributed over the surface of the epidermis, where the articular furrows have no existence. The plan of arrangement of the smaller lines is as follows: A number of straight lines, usually from six to ten, radiate, like the rays of a wheel from its centre, from each hair-pore; these usually come in contact with the lines proceeding from other hairs. These radiating lines thus mark out the surface into triangular spaces, between which are usually situated two or three other pores, those of the sebaceous and sweat glands; from each of these also similar radiating lines proceed; these unite with the coarser lines given off from the hair follicle, and occasion a still further sub-division of the surface of the epidermis into triangular spaces. The result of this minute sub-division is to occasion the whole surface of the epidermis to assume a minutely and beautifully reticular appearance. The coarser lines are best seen in the palms of the hands and soles of the feet, while the smaller and finer lines may be readily traced, following the disposition just described on the back of the hand.

The effect of water in rendering the cells of tesselated epithelium white and opaque has been referred to: its long-continued application to even the living epidermis produces a similar result, which most persons must have observed, although some would be at a loss to account for it; thus, the skin of the fingers of those who have been engaged in washing for some hours becomes of a pearly whiteness.

It sometimes happens that epidermic cells are developed in increased and abnormal quantities, giving rise to tumours, and which are by no means of uncommon occurrence.

EPIDERMIS OF THE WHITE AND COLOURED RACES.

Between the epidermis of the white and the coloured races there is a perfect identity of structure ; the only difference is, that the young epidermic cells of whites contain little or no colouring matter, or pigment granules, except in certain situations, while those of blacks are filled with them; this difference can scarcely be regarded as permanent or structural ; it is one rather of degree than kind, and over which, moreover, climate exerts an all-powerful influence.

We have continual opportunities of witnessing the effect of climate in increasing .the amount of pigmentary matter in the skin. All have noticed that after a few years' residence in a hot country, the skin of many individuals becomes several shades darker than it was previously, and that even the inhabitants of the same country are darker during the summer than in winter.

It would appear, therefore, to be very possible that climate alone, operating through many ages, would be sufficient to change the colour of the skin from white to all the varying shades of red, olive, and black, met with among the different families of the human race.

DESTRUCTION AND RENEWAL OF EPIDERMIS.

The epidermis, like the epithelium, is constantly undergoing destruction and renewal; the evidences of this are, however, more obvious and striking in the case of the epidermis, than were those adduced in proof of the destruction of the epithelium.

Thus the destruction of the epidermis is proved by a variety of facts: By the gradual disappearance from the skin of indelible stains, such as those produced by nitrate of silver or nitric acid.

By scraping the soles of the feet after immersion in warm water; the white and powdery material which is obtained, often in large quantities, examined with the microscope, will be found to consist of epidermic scales.

By the use of the warm bath; floating on the surface of the water will be observed more or . less of a thin and whitish scum ; this consists of desquamated epidermis.

By rubbing the moist skin with a rough towel; a considerable amount of epidermis, visible to the naked eye, will be removed.

The skin of new-born children is frequently observed to be covered with a white and soap-like crust; this, examined with the microscope, will be found to consist of epidermic scales mixed up with sebaceous matter.

The last proof to be adduced of the desquamation of the epidermis is one derived from disease; after inflammation of the skin, whether that of erysipelas, scarlatina or measles, the epidermis peels off, a new one being previously formed beneath the old.

Among many of the amphibia and reptiles, the casting of the epidermis is a periodical occurrence; in man, on the contrary, it is a constant and gradual process normally, although it is also occasionally periodic from disease.

USES OF THE EPIDERMIS.

The principal uses of the epidermis are threefold.

The first and chief use is to serve as a protection to the more delicate parts which lie immediately beneath it.

The second is to prevent the too rapid dissipation of the caloric of the system.

The third use has reference to secretion. It is evident, however, that the importance of the epidermis as a secreting organ is not considerable, seeing that the external surfaces of the body do not require to be kept moist, to the same extent as the internal." That the epidermis does not very actively administer to secretion might be inferred from the* transparency of the fully-developed cells, the faintness of the nuclei, and the paucity of the granules contained within them.

Epidermic cells are also capable of absorption, a fact which their change of colour after long immersion in water testifies.

By far the best description of the anatomy of the epidermis which has fallen under my notice is that contained in the admirable chapter on the Anatomy and Physiology of the Skin attached to the second edition of Mr. Wilson's work on the Diseases of the Skin.


EPIDERMIS.

[In the paper by Mr. Rainey, referred to in the Appendix, he divides the epidermis into two layers, the superficial layer or cuticle, and the deep layer or rete-mucosum of other authors. The deep layer rests on the basement membrane covering the papillae, and fills up the grooves between them: this layer is composed of nucleated cells, in different stages of development: those below being very small, probably only cell nuclei, those in the centre are most perfect, and those above approaching the condition of epidermic scales.

The superficial layer, or cuticle, extends from a little beyond the apices of the papillae to the surface, and consists of flattened cells, which have become converted into scales. These scales are not affected by action of acetic acid, or strong solution of potassa, while by these reagents, the nucleated cells are entirely destroyed.

In the Appendix, already alluded to, the author has referred to the statement made by Mr. Rainey, that no true duct from the sudoriparous glands exists in either layer of the epidermis, the passage being a spiral one through the epidermic cells and scales. ( Vide Plate LXXV1IL, figs. 1, 2.) The lining of the sudoriparous duct, separated with the epidermis after maceration, is the epithelial lining of the duct, and not the entire duct, as stated by some writers.

The epidermis may be readily examined in thin vertical sections made with the Valentin's knife, or sharp scalpel. The fresh skin will be found best for this purpose, and those portions from the heel or palm of the hand show the structure best: these maybe farther dissected with the needles under the microscope and in water, and other sections may be treated with acids and alkalies. In some instances, thin sections can be better made when the skin has been hardened, and rendered more firm than in its natural state.

For this purpose, a strong solution of carbonate of potassa, diluted nitric acid, or sulphuric ether, may be used. When sufficiently thin sections can be obtained without this process, the structure is more readily made out, and with a good Valentin's knife, this is not usually difficult to do. By continued maceration, the epidermis may be separated in layers ; this process is necessary to exhibit well the deep layer or rete-mucosum.

When desired, sections of epidermis may be mounted in fluid for preservation : but in this condition they will be of little service, unless to show the spiral passages and external orifices of the sudoriparous ducts. The retemucosum is also best preserved in fluid.]


Article XI. The Nails

The horny appendages of the feet and hands, the nails, do not constitute a distinct structure or type of organization in themselves, but are merely modifications of one which has already been described, viz : the epidermis.

Nails, therefore, consist of cells similar to those of which the epidermis is itself constituted, with the difference that they are harder, drier, more firmly adherent to each other, and that in the majority the nucleus is obliterated. (See Plate XXV.)

To display the cellular constitution of nails, some little nicety is required; it may be shown, however, in the thin scrapings of any fragment of nail submitted to the microscope, as also by soaking the nail in a weak alkaline solution, and which, acting upon and dissolving the inter-cellular and uniting substance, sets free the cells.

The cellular structure of nails may also be shown, even without previous preparation, by a careful examination of the root and under surface of the nail, in which situations young and nucleated cells may usually be detected.

The younger nail cells, like those of the epidermis in the coloured races, contain pigmentary matter.

Nails, however, are not simply constituted of super-imposed and adherent cells, but these are regularly disposed in layers or strata, each of which probably indicates a period of growth.

These layers, marked by striae, may be clearly seen on any thin section of nail, whether longitudinal or transverse; they do not appear to follow any very definite course; usually in a longitudinal slice, they run from above, downwards and forwards; sometimes they are horizontal, but I have seen instances in which the striae were directed obliquely backwards, in place of forwards. In the transverse section, the striae are less strongly marked, and run usually moi'e horizontally. (See Plate XXV.) Occasionally they are seen to pass in opposite directions, and to decussate. I am disposed to think that the one set of striae visible are rather apparent than real, and are produced by the knife employed in making the section.

It is usually easy to distinguish the superior from the inferior edge of a slice of nail; the former will generally appear quite smooth, while the latter will be rough and uneven. (See Plate XXV.)

Such is a brief sketch of the structure of nails:* their form, position, and mode of connexion, may next be considered.

Each nail may be said to be quadrilateral and convex from side to side, as it is also very generally from before backwards ; the three posterior margins are received into a groove formed by a duplicature of the dermis and epidermis, the anterior margin alone being free. The root and sides of the nail, the former consisting of about onefifth of its extent, are intimately attached to both surfaces of the groove; the inferior aspect of the body of the nail is likewise firmly adherent to the derm beneath it, except for a small distance at its anterior part.

The nail, then, is attached to the dermis by its root, and by a portion of its inferior surface; this attachment, however, is scarcely to be considered as structural, since it consists of a mere adaptation of the opposing surfaces of the dermis and nail. The surface of the dermis upon which the nail rests, it is known, is not smooth, but is raised into papillae ; to these the nail adapts itself, and in this way the two become intimately united.

It is in this manner, also, that the longitudinal lines observed on most nails are produced, and the appearance of which has induced some observers to entertain the idea that they are of a fibrous, and not a cellular constitution.

Nails are, to a considerable extent, hygroscopic, becoming by the imbibition of fluid soft and yielding.

DEVELOPMENT OF NAILS.

Nails are developed somewhat differently from the epidermis, of which we have stated that they are a modification; thus, they do not increase by the equal development of new cells on the entire of their under surfaces, but they grow from a point, from the base or root of the nail.

The reality of this mode of development becomes evident from the following considerations:

1st. That the younger nail cells are found principally at the root of the nail.

2d. That if the relative situations of two spots or stains be observed, it will be seen that during the growth of the nail, they preserve precisely the same relation with each other, only that they gradually approach the end or free margin of the nail, which at length they reach, and from which finally they are worn away. This observation proves the absence of interstitial growth, and shows that the nail increases in length by additions made to the root.


  • The first exact description of the nail and of the disposition of the derm which

supports it was given by Albinus (Adnotal. Acad. lib. ii. 1755, p. 56), but Schwann showed that the nail had a lamellated structure, and that the lamellaj are composed of epidermic scales. (Mikroskopische Unlersuchungen, 1839, p. 90.)


Although it is certain that the longitudinal growth of nail occurs by the development of cells at the root, yet it is also evident that its thickness is increased by the formation of new cells on its under surface, where they may usually be detected with the microscope in a partially developed state. This double development explains why the nail is thinnest at the root, where only a single method of growth prevails.

The junction of the root with the body of the nail is indicated by a semi-circular line, and the former is not merely thinner than the latter, but it is also softer and whiter; whiter in consequence of the subjacent dermis containing in that situation fewer blood-vessels, and its papillae being smaller.

From the pi-eceding account of the development of nails, it follows that when these sustain any loss of substance on their upper surfaces, this loss is never repaired, but remains without alteration until it reaches the free margin of the nail.

Epithelium, epidermis, nails, and some other structures of the body, never seem to attain to a stationary state; they are throughout the w T hole of life undergoing a process of development; this, in the case of the nails of man, renders the interference of art necessary to remove from time to time the redundant growth.

It is probable, however, that if the nails were not cut, but allowed to grow at will, they would not exceed a certain length; among the Chinese, who do not pare their nails, they are usually about two inches long.

Nails doubtless sustain a loss of substance beyond that which they experience from occasional cutting, as from friction and the desquamation of the cells from the inferior and anterior portion of each nail, and which may be inferred to take place from the fact that the matter which accumulates beneath the extremities of the nails is to a great extent made up of epidermic or nail cells.

It has been estimated that the entire body of a nail, from the root to its free margin, is developed in from two to three months.

The third month of intra-uterine life is the earliest period at which the nails can be detected ; they then consist of nucleated cells, and rather resemble soft epidermis than the hard and horny texture of fully-developed nails.

A nail which has been once entirely destroyed is always regenerated in a very imperfect manner, it being usually seamy and irregular in consequence of the disturbance and injury sustained by the adjacent dermis, and the markings of which are impressed upon the nail.

Nails are subject to deformity in certain chronic maladies of the heart and lungs, especially in cyanosis and phthisis. It has been suggested that this may depend upon the state of the circulation in the vessels of the dermis.

The various modifications of nail met with throughout the animal kingdom, the claws of birds and carnivora, the hoofs and horns of ruminants, have essentially a similar structure to the nails of man. The hoof of the horse and of some other animals is traversed from above downwards by the spiral ducts of the sebaceous glands.


NAILS.

[The structure of nails is examined in thin sections and scrapings, placed in the field of the microscope, and covered with a drop of water, or oil of turpentine.

The secreting vessels of the nail, so well described by Mr- Rainey in his paper quoted in the Appendix, can only be seen after injection, and the removal of the nail. A foetal subject is well adapted for this injection. A hand or foot of an adult may sometimes be so well filled as to exhibit these vessels.

The sections or scrapings of the nail, may be preserved dry, in fluid, or in balsam, the choice depending on the thickness of the specimen. The injected matrix, &c, is best preserved in fluid; for this purpose, alcohol and water, or Goadby's B-solution, may be employed,

See Appendix, page 541.

Plate LXXI. represents the different vessels as described by Mr. Rainey.]


Article XII. — Pigment Cells

Colouring matter is found in the animal organization in two states, either diffused throughout the fluid contents of colourless cells, as in fat cells generally, but especially in those of the iris of birds, and as in the liver cells, and red blood discs, or it is limited to the granules contained in certain peculiar cells, the parietes of which are also colourless, which have received the name of pigment cells, and which we are now about to describe.

Pigment cells have precisely the same structure as those of epithelium and epidermis, the description of which has just been brought to a conclusion; that is, they consist of cell wall, nucleus, cavity, and granules; the only difference between the two is, that the granules in the one case are coloured, and in the other colourless: as may be inferred from their similarity of organization, a similar mode of development prevails in both.*

All the varieties of colour of the eye and of the skin, observed among the different members and families of the human race, depend upon the number of pigment cells and the shade and intensity of the colouring matter enclosed within the pigmentary granules; the deeper the colour, the more abundant the pigment cells, and the greater the depth of colouring contained in the granules; thus, of course, the pigment cells scattered beneath the epidermis of the Ethiopian are far more numerous than those found beneath that of the white race, and the colouring; matter of the granules is doubtless also darker.

In the white, however, a greater or less number of pigment cells is. almost invariably found in certain situations, as in the eye, on the internal surface of the choroid, and the posterior aspect of the iris and ciliary processes, also between the sclerotic and choroid; in the skin at certain localities where it is placed beneath the dermis and epidermis, as in the areola round the nipples, especially of women, and about the perinaeum and genital organs.

In the black races, pigment cells follow a similar distribution in the eye; but beneath the epidermis, as also under the nails, they form a continuous stratum composed of super-imposed layers of cells.

  • Mondini (Comment. Bonon, t. vii. 1791, p. 29,) was the first observer who made

accurate microscopic observations on the pigment of the eye. He stated that the pigment is not simply mucus, but a true membrane formed of globules disposed in quincunx. The son all but completed the work which the parent began : he found that each globule is made up of little black points. Finally, Kieser (Be Anamorphosi Oculi, 1804, p. 34,) described the pigmentary membrane as a cellular tissue containing corpuscles.


There are yet other situations in which pigment cells have been encountered : thus, Valentin* has signalized the occurrence of pigmentary ramifications in the cervical portion of the pia mater, to which they impart a blackness perceptible to the unaided sight.

Again, Wharton Jonesf has described a thin but evident layer of brown pigment in the membranous labyrinth of the ear of man. It has been observed in other mammalia, in which it is still more marked, in the same situation, by Scarpa, Comparetti, and Breschet. J

The brown spots, known by the name' of freckles, with which the faces of most persons are more or less covered in summer, are due to a development of pigment cells.

A development of pigmentary matter frequently takes place as the consequence of disease; thus, it is of common occurrence to meet with growths either entirely or in part composed of pigment cells, the tumours, with the proper structure of which it usually thus intermingled, being those of cancer or medullary fungus.

The nature of the pigment-like matter found in the lungs and bronchial glands of aged persons and animals has been the subject of much discussion ; nor has it been as yet decided whether it be true pigment, or merely a deposition of carbon. Pearson§ maintained the opinion that the colouring matter is the powder of carbon, since neither chlorine nor the mineral acids act upon it.

In those remarkable lusus natures, Albinoes, there would appear to be an absence of pigmentary granules in all parts of the body, even in the eye: the pigment cells themselves are stated to exist, but to be wanting in their characteristic coloured contents.

Pigment cells do not present the same size, form, and character wherever they are encountered.

Thus, those of the choroid are adherent, large, flattened, polygonal, mostly hexagonal, with clear nuclei and margins; occasionally, however, it happens that both nuclei and cell wall are obscured by the number and disposition of the contained granules : the cells are mostly of uniform size as well as shape, in consequence of which regularity they form a very beautiful microscopic object; sometimone cell is observed to be larger than the rest, octagonal, and surrounded by a number of cells of smaller size than ordinary, and mostly pentagonales, however,

  • Verlaufund Enden der Nerven, p. 43.

f Article Hearing in the Cyclopaedia of Anatomy and Physiology, t. ii. p. 529.

I Rtcherches sur VOrgane de VOiiie de V Homme, Paris, 1836, in 4to.

\ Philosophical Transactions, 1813, pi. ii. p. 159


According to Henle,* the contained granules are situated in the posterior part of each cell, while the nucleus is placed in its anterior division ; it is this arrangement which allows of the nucleus being so clearly seen ; in those cases, however, in which the nucleus is obscured, acetic acid will frequently bring it into view; this, if concentrated, will dissolve the cell wall, set free the granules, and leave the nucleus.

Schwann states that he has seen the pigmentary granules in the cells of the choroid in active motion.

The cells of the choroid form by their adherence a membrane resembling the most regular and beautiful mosaic pavement in miniature.

The pigment cells of the posterior face of the iris and ciliary processes are smaller than those of the choroid, are for the most part round, or approach that form, and so filled with the corpuscles that the nucles and margin of the cell is not usually visible.

In the skin, the pigment cells are placed between the dermis and epidermis ; they do not there form a layer of equal thickness, but accumulate in the depressions left between the papilla?, forming many super-imposed layers, while on these they are spread out in a single thin layer, and are often much scattered. It is to this circumstance, as well as the thickness of the epidermis, and the state of repletion of the cells, that the varying shades of the colour of the skin of the same individual depend. In the negro, the cells resemble much in form those of the choroid, being either perfectly hexagonal, polygonal, or irregularly rounded ; the nucleus can be well seen in those cells which are less filled.

Among the white race, the pigment cells in those situations in which they occur beneath the skin are fewer in number, smaller, more rounded, and frequently resemble little masses of corpuscles rather than distinct cells; nevertheless it is even here sometimes possible to distinguish the nucleus and cell wall.

There exists between the internal face of the sclerotic and the external of the choroid a fibrous tissue of a brown colour; this, when these two coats of the eye are separated, remains attached in part to the one, and in part to the other; that, however, which adheres to the sclerotic has received a distinct name, and is called lamina fusca.

  • Anat. Gen. vol. vi. p. 295.

Now, the colour of this layer is due to the presence, scattered among the fihres, of pigment cells of a very peculiar form and construction ; they are mostly very irregular in size and shape, are marked with a clear central spot, which indicates the locality of the nucleus, and from the margin of many of them proceed filamentous processes of variable number and size, and the extreme points of which are mostly colourless, and are not dissolved by acetic acid.

Pigment cells of analogous construction exist on the external surface of the choroid, and also on the cervical portion of the pia mater.

Mixed up with perfect pigment cells a greater or less number of pigment granules are always observed ; these are among the smallest objects in nature, and, on account of their minuteness, it is in them that molecular action in all its activity is best seen: they are not spherical in form, but are flattened, so that they appear as discs, lines, or points, according as the surface, side, or end presents itself to the eye of the observer.

It is probable that it is by means of these granules that pigment cells are multiplied.

Climate, and particular states of the system, as pregnancy, have much effect in increasing the amount of pigmentary matter beneath the skin; from the latter cause, the areolae around the nipples frequently become of a deep chocolate colour. Of the influence of the former, it is scarcely necessary to cite examples : it may be remarked, however, that freckles are due to the development of pigment cells, brought about by the action of the summer's sun.

This augmented development of pigment cells may be rationally explained by the increased determination of blood to the dermis of the breast from increased activity of function in that organ during pregnancy, and to the general surface from the effect of the sun's heat.

It is questionable whether all the varieties of colour of the human species have not originated in climateric causes, operating through many ages.

It may also be questioned whether pigment cells are not susceptible of being developed into those of the epidermis. If the epidermis of a negro, raised from the surface by means of a vesicatory, be examined with the microscope, it will be noticed that the most external cells contain a considerable amount of colouring matter, which, as this resides in solid granules and not in a fluid, it is difficult to suppose had entered the cells by endosmosis.

Pigment cells are capable of regeneration, in a part in which they have been destroyed: it is necessary, however, that the subjacent dermis be not too deeply injured ; the cicatrices remain for a considerable time nevertheless without colour.

The skin of the children of negro women does not acquire its full depth of colouring for some days after birth.

Pigment cells are developed at a very early period of intra-uterine life. The uses of pigment in the skin are not well understood; that in the eye is doubtless of importance in the discharge of the functions of that organ: it is known that the Albinoes, in whom it is either absent or exists but in small quantities, are incapable of supporting a strong light.

Pigment cells of particular forms occur among some of the lower animals. Those of the internal surface of the choroid of fishes and birds, situated in front of the ordinary coloured cells, have the form either of short sticks or clubs. The argentine pigment of the iris and peritoneum of fishes is composed of elongated corpuscles. The pigment cells placed beneath the epidermis of the frog are for the most part stellate.


PIGMENT CELLS.

[Pigment cells are most readily studied on being detached from the choroid coat of the eye, by means of a fine needle. On rupturing the cells, the pigmentary matter escapes ; and with a high power of the microscope, numerous black or brown molecules will be observed. These molecules measure from TT i n to g jio o of an incn in diameter.

These cells may also be studied with advantage in the cuticle of the negro, which may be detached after slight maceration, and also in the skin of the frog.

The pigment cells in the frog, will be found to consist of long, irregular, jagged processes.

Cells containing pigmentary matter are well preserved in the flat cell with fluid.]


Article XIII. — Hair

We now come to the description of another epidermic modification, viz: hairs; these, however, are much more complex in their structure than any which have been hitherto described, and are less obviously derived from the epidermis.

As in the case of most of the solids described in this work, we shall first discuss the different particulars relating to form and size, and next proceed to the description of structure.

FORM OF HAIRS.

Hairs consist of two parts, a root and a stem : in speaking of the form of hairs, reference is made to the latter. Hairs, then, are elongated, and more or less cylindrical developments of the epidermis. They depart, however, in most cases, from the character of a true cylinder in two respects; first, they are not perfectly spherical, but are seen to be, when viewed transversely, either oval, flattened, or reniform (see Plate XXIX.) ; and secondly, they are not of equal diameter throughout, being thickest at about the junction of the lower and middle thirds of the stem, of smaller diameter from this part downwards towards the root, and still more reduced in size as the free extremity is approached, and which, in a hair which has not been recently cut, terminates in a point, the diameter of which is frequently several times less than that of the more central parts of the shaft. (See Plate XXIX.)

This form is best seen in hairs of medium length, as those of the whiskers, eyebrows, axillae, and pubis, in which also the flattened and oval shapes are principally detected.

The hairs which approach most closely the cylindrical, are those of the scalp.

Henle* makes the interesting statement, that the curling of hair depends upon its form, and that the flatter the hair, the more it curls, the flat sides being directed exactly towards the curve described. From this it follows, that the hair of negroes would exhibit in a very marked manner this flattened form.

  • Anat. Gen., vol. vi. p. 314.


SIZE OF HAIRS.


Hairs differ remarkably in size, both as regards length and breadth: they differ not merely in different individuals, in different localities 'in the same person, but also in any one given situation, as the scalp or pubis.

The hairs of the scalp are the longest; those of the scalp of women are many times longer than those of the same part in man, and according to the measurements of Mr. Wilson, they are also thicker. Next in length come the hairs of the chin of man. Among women, instances have been known of the hair extending from the scalp to below the feet, and the beard of man not unfrequently reaches to the waist.

The shortest and smallest hairs are those covering the general surface of the body, and which are reduced to mere down (lanugo).

The thickest hairs of the body are those of the whiskers, chin, pubis, and axilla?; the finest, those distributed over the general surface; the hairs of the scalp are of intermediate diameter.

The hairs of children are finer than those of adults, and those of the head of men than those of women.

It cannot be doubted but that frequent cutting and shaving of the hair tends to increase its thickness.


STRUCTURE OF HAIR.


Each hair admits of division into two parts, the root and stem; and each of these, again, allows of still further sub-division : thus, the root consists of the prolongation of the hair proper, or stem, terminating in an expanded portion, which has been termed the bulb, and of a double sheath; the stem also is divisible into cortex, medulla, and intervening fibrous portion, which constitutes the chief bulk of the hair. (See Plates XXVIII. and XXIX.)

These divisions of the root and stem of hairs suggests its comparison to a tree, the stem of which also resolves itself into cortex, medulla, and intervening woody or fibrous substance. The comparison is also heightened by the similar relation in which both stand to the parts around them, viz : the soil in the case of the tree, and the dermis in that of the hair.

ROOT OF HAIR.

We will first describe the root, because it is the source from which the hair is developed: this, as already noticed, consists of two parts, the sheath and the bulb.

The Bulb. — The bulb is the expanded and basal portion of the stem of each hair : it is usually two or three times the diameter of the hair itself, and is sometimes excavated below : it is constituted of granular cells, which are either circular, angular, or elongated in form ; the spherical cells, form the extremity of the bulb, the polygonal ones its surface, and the elongated cells are placed above the spherical ones, of which they are modifications, and beneath the angular cells of the surface of the bulb. Acetic acid will be found useful in displaying the cellular structure of the bulb.

In healthy hairs this bulbous portion of the stem is always coloured, which is not the case with gray hairs. (See Plate XXVIII.)

The part of the stem of the hair immediately above the bulb, andincluded within its sheath, exhibits the structure of the body of the stem itself, being divisible into scaly cortex, fibrous intervening substance, and granular medulla.*

Sheath. — The bulb and lower portion of the stem of the hair is included in a sheath consisting of two distinct layers, an outer and an inner. (See Plate XXVIII. fig. 1.)

The outer layer is an inversion of the epidermis : it first merely encircles the portion of the stem of the hair beneath the level of the epidermis : it next surrounds the inner layer of the sheath, to which it soon becomes intimately adherent; finally, it forms a cul-de-sac around the bulb of the hair.

The fact of the inverted sheath of the epidermis forming a pouch around the bulb of the hair, may be inferred from the circumstance, that when the epidermis peels off as the result of decomposition, the hairs usually come away entire with it ; its continuation, moreover, around the bulb may be shown in transverse sections of the skin of the axillae and whiskers, in which the hairs penetrate into the subcutaneous fatty substance. (See Plate XXVIII. fig. 1.)

This outer layer is colourless, is possessed of considerable thickness, and is evidently made up of granular cells similar to young epidermic cells.

In most hairs, whether coloured or uncoloured, which have been forcibly removed from the skin, this outer layer is usually torn across, the rupture occurring almost invariably at a little distance from the bulb of the hair: the root of the hair, then, below this breach of continuity, consists only of the inner layer of the sheath and of the stem of the hair ; and at this situation the root, to the naked eye, appeacontracted: this is, however, but an appearance, the result of the absence of the outer layer, and of the expansion of the stem into the bulb. (See Plate XXVIII. fig. 2.) rs

  • See Appendix, p. 549.


The inner layer of the sheath is an eversion or revolution of the epidermis, and is an offset or continuation of the outer layer, commencing at the lower part of the bulb : it is colourless, possessed of considerable thickness, its diameter being about one-third of that of the stem of the hair in its thickest part : it tears readily in the longitudinal direction with a somewhat uneven fracture ; and hence maybe inferred to be of a fibrous constitution, as may be shown to be the case : its inner surface is marked with reticulated lines, the impressions of the cortical scales of the shaft of the hair.

This inner layer is not of equal diameter throughout, but tapers gradually from below upwards: it is well defined both internally and externally, except where it comes in contact with the bulb internally, with which its inner edge or surface becomes incorporated; above, it terminates in a thin border at a little distance below the level of the skin. (See Plate XXVIII. fig. 1.)

The outer layer, although adherent to the inner at its lower part, does not become incorporated with it : the latter, except at the point indicated, preserves every where its independence and individuality. The two layers, it will thus be seen, might with much convenience have been described, as two distinct sheaths, an inner and an outer: to do so, would be, however, to lose sight in some measure of the similar origin and nature of the two.

In the fact, however, of the inner sheath exhibiting a fibrous structure, and of its incorporation with the bulb, it would appear to have more structural affinity with the fibrous portion of the stem of the hair itself than with the outer layer or cellular sheath.

This inner layer might be appropriately termed the "modelling sheath," since it doubtless regulates the form and dimensions of the shaft of the hair, the substance of which when first developed is soft and plastic. Henle describes the inner layer as fenestrated : this structure I have never seen exhibited.

Shaft of the Hair.

The stem or shaft of the hair is divisible, as already observed, into cortical, medullary, and fibrous portions.

Cortex. — The cortical part of the hair consists of a layer of scales, imbricated upon each other after the manner of tiles upon the roof of a house. (See Plate XXIX.) These scales are best seen in the larger hairs of the whiskers and pubis, and in the small downy hairs; they are smaller than the ordinary cells of epidermis, and are rarely seen to be nucleated. Maceration of the hair in sulphuric acid causes them to fall off, and in this way their size, form, and structure, may be satisfactorily studied.

The scales are absent from the points of the finer hairs. In consequence of their imbrication upon each other, their little thickness, and of the double contour presented by their free edges, they frequently convey the appearance rather of anastomosing fibres running round the hair than of distinct scales.

A hair rolled between the fingers always advances in a given direction, viz: towards the apex: this results in part from the tapering form of the hair, and partly from the more or less spiral disposition of the scales.

Fibrous Layer. — The fibrous portion of the stem of the hair constitutes its chief substance and bulk, forming two-thirds of the entire diameter, one-third on each side of the medulla. In hairs which are not too dark, the constituent fibres may be seen in situ: they are most palpably brought into view either by scraping the hair with a knife or by crushing it after masceration in sulphuric acid : they are also best seen in the larger hairs and near the centre of the shaft.

Henle describes the fibres as flat, with uneven edges, and is in doubt as to whether they are branched or not. To my observation they appear much smaller than they are stated to be by Henle, and are spherical and simple. (See Plate XXIX.)

These fibres have a cellular origin, and are formed by the elongation of the inner cells of the bulb, in which their gradual extension into perfect fibres may be traced.

• They are stated by most observers not to extend to the extreme point of the hair; and the same statement is likewise made in reference to the medullary canal and cortical scales. Of what, then, it may be fairly asked, is the point of the hair constituted, since every structure entering into the formation of the shaft is denied to it? The assertion that the fibres do not extend to and form the apex of the hair is evidently erroneous. In the examination of the points of a number of hairs which have not been recently cut, fibres, often separated from each other and loose, will frequently be detected. (See Plate XXIX.)

The whole of the fibres of the stem, however, do not extend its entire length, the majority terminating long before the extremity is attained; and it is to this fact that the attenuated form of the hair is attributable. In some hairs the fibres are seen to terminate at regular distances, their points describing transverse lines on the stem of the hair.

The splitting, of such common occurrence in hairs which are allowed to attain an excessive length, is due to a separation of the fibres from each other.

The fibrous portion in young and healthy hairs is coloured. Medullary Canal and Medulla. — In most hairs which are not of too deep a colour a medullary canal may be detected running up the centre. This commences in the upper portion of the bulb, runs along the shaft, but ceases as it approaches the apex: its diameter varies with that of the hair itself, but usually bears the proportion of a third of its thickness. (See Plates XXVIII. and XXIX.)

Henle is uncertain whether this canal is lined by a distinct membrane or not, but inclines to the opinion that it is so.

The medulla or contents of this canal exhibit a granular appearance, and are made up of pigment granules, a few perfect pigmentary cells, and particles of coloured oil ; it is therefore in the medulla that the greatest amount of colouring matter of the hair is situated. (See Plate XXVIII. fig. 1.)

At the very commencement in the bulb of the hair, the medulla has distinctly a cellular origin.

In young and healthy hairs it is also continuous throughout the entire extent of the medullary canal; in old and discoloured hairs, on the contrary, its continuity is frequently interrupted by distinct intervals, and it only partially fills the cavity of the canal .even where it is present.

The medullary canal and medulla is best seen in the larger hairs, which are not of too deep a colour, and in gray hairs: in the fine and downy hairs of the general surface of the body, the canal and its contents, as a necessary consequence, are almost entirely absent. In some rare instances, two medullary canals have been observed in the same hair. In the sable, the medulla has a distinctly cellular structure throughout.*

  • The first accurate observations on hair were made by Hook, Micographia, 1667,

Obs. 32. tab. v. fig. 2., and Leeuwenhoek, Opera, t- iv. p. 46.


HAIR. 297


FOLLICLE OF THE HAIR.


Each hair is implanted in a distinct depression in the dermis, the base of which especially is freely supplied with nutrient vessels: this depression is also lined by an invagination of the epidermis, and which becomes ultimately the outer layer of the sheath of the root of the hair as already described. (See Plate XXVI. fig. 3.)

Between this layer, however, and the shaft of the hair for a short distance before it rises above the level of the skin, a space or cavity is left; into this space the canals of one or more sebacious ducts generally open, and in it also entozoa frequently develope themselves.

It sometimes happens that two or more hairs are contained in the same follicle (see Plate XXVI. fig. 3) : in these cases, however, each hair has a distinct modelling sheath. In some animals, the location of a number of hairs in one sheath is the ordinary mode of arrangement; in the pig, for example, the hairs are usually thus associated in three's, as also occasionally in man.

The hair follicle or crypt is best seen by examining thin vertical slices of the skin.

The length of the hair follicle and the consequent depth of implantation of the hair varies, but is often equal to the twelfth or sixteenth of an inch ; the hairs of the head, of the whiskers, of the pubis, and of the axillae, penetrate into the sub-cutaneous cellular tissue; those of the eyelids and ears, to the subjacent cartilages : the roots of hairs in genera], however, do not penetrate beyond one-half the depth of the corium, in the substance of which they are buried.

It is usually stated that the bottom of the follicle is occupied by a papilla furnished with blood-vessels and nerves, on which the bulb of the hair immediately rests ; and that it is owing to this papilla that the base of the bulb, when removed, exhibits a concavity. This description, in the case of tactile hairs, may be correct, but is surely not so when applied to hairs in general. Each hair does indeed rest upon a papilla, but it is one which is destitute of blood-vessels and nerves, and which is cut off from all direct vascular communication by the cul-de-sac formed by the outer lamina of the sheath. This papilla may be described as a compound cellular vesicle, and is probably the true germ of the hair; it is on it that the bulb of the hair is situated, and which occasions the depression which this generally displays when it has been forcibly extracted. This germ is best seen in gray and light-coloured hairs.


298 THE SOLIDS


GROWTH OF HAIR.

The growth of hair takes place at the root, and is the effect of the development of new cells, which is continually in progress in the bulb, and which afterwards become modified into those of the scaly cortex and fibrous stem ; these new cells, coming behind the older ones, continually press them forwards, and thus occasion the elongation of the hair.

But the elongation of each hair takes place in a manner very different from that just mentioned, not from the development of new cells, but by the gradual elongation and extension of the cells already formed after they have quitted the bulb, and when they come to form the shaft of the hair. This mode of elongation — it can scarcely be called development — is proved by the gradual tapering of the hair which takes place after the point has been removed: of the truth of this fact, not the slightest doubt can be entertained.

At the period of puberty, a growth of hair takes place in certain situations in which previously it was not apparent, as on the chin, cheeks, in the axillae, and on the pubis, abdomen, and chest; this development is an effect of the great functional activity which exists at that period, and which is the occasion of the increased and rapid growth of the several constituents of the body which then takes place.

The earliest periods at which the rudiments of hairs in the human fcetus have been observed is from the third to the fourth month : the hair follicle is formed in the first place, next the bulb, and then the sheath and stem of the hair, which, in the early period of its development, is curved upon itself.

Hairs are occasionally developed in certain peculiar situations, as on the mucous membrane of the conjunctiva, the intestines, and gallbladder, in the ovaries, and in steatomatous and encysted tumours.

Hairs may be transplanted, and, it is said, will grow after such transplantation in consequence of the adhesions and organic connexion established between them and the adjacent tissues — a fact of which practical advantage might be taken if correct.

When a hair has obtained the full term of its development, according to the researches of Eble, it becomes contracted just above the bulb : this change probably announces its death and approaching fall.

REGENERATION OF HAIRS.

Hairs are peculiarly susceptible of being affected by the condition of the health, even more so than the epidermis. If this be vigorous,


HAIR. 299

as a rule to which there are many exceptions, it will be found that the hairs themselves are thick, and firmly set in the skin: if, on the contrary, the powers of the system be debilitated from any cause, the hairs will either fall off spontaneously, or a very slight degree of force will serve to dislodge them from their connexions.

If the bases of those hairs which fall out of themselves be examined, or which are removed by combing and brushing, it will be seen that the bulb alone has come away, the entire sheath and germ remaining behind. In such cases, the hair is doubtless regenerated, and after its regeneration, is usually stronger than it was previously. (See Plate XXIX.)

It has not yet been ascertained by positive experiment whether the hair is capable of reformation in those instances in which both bulb and sheath have been removed: it is most probable, however, that where they have been entirely abstracted, no renewal of the hair could ensue.

It is possible that in some cases the apparent regeneration of the hair arises, not from the development of new hairs in the primitive sheaths and upon the old germs, but from the formation of new hair follicles and germs : of this, however, no proof has as yet been given.

That a regeneration of new shafts of hair is continually in progress, whether from new germs or the older ones is not known, is proved by the detection of small and pointed hairs just emerging from the skin in the scalp of even old persons.

NUTRITION OF HAIR.

Hairs are nourished in the same way as the epidermis itself; that is, they do not receive into their own structure either blood-vessels or nerves, but derive their nutriment from vessels which are so distributed as to come into close contact with the tissues to be nourished.

This indirect reception of the nutrient plasma explains the very great susceptibility of the epidermis and its several modifications to be influenced by causes affecting the general health, and in consequence the circulation and the qualities of the circulating fluid.

The epidermic tissues being placed in situations the most remote from the centre of the circulation, are endowed with but a feeble degree of vitality, and which is readily destroyed by causes affecting the amount and nature of the circulating fluid received by them.

The nutrient vessels and sentient nerves of each hair are distributed around and outside the sheath, and not in a raised papilla, as generally described, although this may really be the case in the large hairs of the whiskers of some animals, as, for example, the tactile hairs of the seal, &c. The fact of the hair usually penetrating below the level of the true skin and into the sub-cutaneous fatty tissue seems to disprove the notion of a distinct and vascular papilla.

DISTRIBUTION OF HAIRS.

Hairs are distributed over the entire surface of the body, with the exception of the palms of the hands, soles of the feet, and last phalanx of the toes and fingers : there are, however, situations in which they are developed in increased quantities, as on the integument of the scalp, on that of the eyebrows, on the margins of the ciliary cartilages, and after the period of puberty, on the chin, cheeks, axilla, pubis, abdomen, chest, and at the entrance of the nares and ears.

The number of hairs found in these several situations differs very considerably in different individuals, according to age and condition of health.

Individuals of the male sex also are generally more hairy than females, in whom also no development of hairs takes place on the chin, cheeks, chest, and abdomen.

Of the number of hairs which exist on the entire surface of the body, some idea may be formed from the measurements of Withof. The quarter of a square inch furnished 293 hairs at the synciput, at the chin 39, at the pubis 34, on the fore-arm 23, at the external border of the back of the hand 19, and on the anterior surface of the thigh 13. Upon the same extent of surface, Withof counted 147 black hairs, 162 brown, and 182 flaxen.

Hairs of great length and strength are often developed in considerable quantities in different parts of the body, in moles and naevi.

DffiECTION OF HAIR.

The hair follicles are not placed vertically in the skin, but obliquely, and the hairs which issue from them consequently themselves run in the same oblique direction. (See Plate XXVI. jig. 3.)

The apertures of most of the follicles look downwards, and hence we find in most cases that the points of the hairs, when fully developed, are similarly directed.

In addition, however, to this general arrangement and distribution, it will be seen that in early life the hair follicles are disposed in lines, the apex of one follicle nearly touching the base of the next: the lines


HAIR. 301

thus described are not straight, but are more or less curved, and divergent or convergent, after the manner of the lines upon the case of an engine-turned watch: the hairs which issue from the follicles thus take particular and determinate sweeps, which it is unnecessary to describe in detail.

It occasionally happens, from some cause or other, that the hair follicles are implanted in a manner the reverse of that which should obtain: this is especially seen in those of the scalp of children, in whom frequently certain tufts of hair grow up, and incline in a direction opposed to that of the contiguous hair. This mal-disposition of the hair is the source of much trouble and annoyance to anxious nurses and mothers, who spend much time in endeavouring to bring the refractory lock into order.

In this endeavour there can be no question but that it is possible to succeed, as is proved by the very different arrangement which the hair of the head is made to follow in accordance with the manner in which it is dressed.

ERECTION OF HAIR.

Man, to a certain extent, and many animals in a considerable degree, possess the power of erecting the hairs. This power in man is limited to the hairs of the head, in many animals it is much more general.

Most persons, on sudden exposure to cold, and on experiencing of any emotion of fear or horror, feel a creeping sensation pass over the head: this sensation is accompanied by a certain degree of erection of the hair, but not indeed to such an extent as to cause it " to stand on end." JMow, this erection is the result of the distribution of fibres of elastic and contractile tissue throughout the substance of the corium, and which, interlacing among the hair follicles, occasion the erection of the hairs themselves.

The distribution of these fibres, and their connexion with the bases of the hairs, are well seen in the skin of the hog.

COLOUR OF HAIR.

The colour of the hair depends upon the same cause as that of the skin and eye, and is due to the presence of pigment granules and cells ; these are contained principally in the medullary canal, but are also interspersed between the fibres of the stem ; they first become manifest in the upper portion of the bulb of the hair.

The depth of the colour of the hair very generally bears a relation to the development of pigmentary matter in other parts of the system, as in the eye and beneath the skin. To this rule, however, some remarkable exceptions are occasionally encountered.

The colour of the lighter hairs, as the red and flaxen, would appear to depend less upon the number and depth of colouring of the pigment cells and granules, than upon the presence of minute globules of a coloured oil.

In the hair of Albinoes but little colouring matter is present; and in gray hairs, also, the colour has deserted the pigment cells and granules.

Hair is decolorized by long contact with chlorine.

It is generally stated as an undoubted fact, that the hair may turn white, or become colourless, under the influence of strong and depressing mental emotions, in the course of a single night. This singular change, if it does ever occur in the short space of time referred to, can only be the result of the transmission of a fluid possessing strong bleaching properties along the entire length of the hair, and which is secreted in certain peculiar states of the mind.

GRAY HAIR.

If a gray hair be contrasted with an unaltered one from the head of the same person, the following differences will be noticed between the two. The gray or white hair will be observed to be almost colourless, the bulb and fibrous portion will be destitute of colour, the medulla alone retaining a slight degree of coloration: this, however, is collapsed, and in place of being continuous throughout its length, will be seen to be interrupted at intervals. (See Plate XXVIII. fig. 2.)

The unaltered hair, on the contrary, is distinguished by characters the reverse of those exhibited by the gray hair; thus, the buib, stem and medulla are all deeply coloured, and the latter fills the entire cavitv of the medullary canal, and is continuous throughout. (See Plate XXVIII. ^.1.)

Gray hair retains a considerable degree of vitality, as is proved by its growth continuing for many years after its loss of colour.

PROPERTIES OF HAIR.

Hairs are remarkable for their strength, their elasticity, durability, and for the difficulty with which they undergo the process of decomposition: their strength results probably from their fibrous constitution; in their elasticity and durability, they partake of the character of all horny structures.


HAIR. 303

The strength of hair is proved by the fact that a single hair will bear a weight of 1150 grains.

Its elasticity is shown by the readiness with which each hair, when extended, returns to its original size and shape, as well as by the fact that the numerous hairs forming a curl or lock will recover their ordinary form and disposition after extension.

Its durability is shown by the persistence of hairs throughout many years of life.

Lastly, its indestructibility is proved by the occurrence of hairs in the tombs of persons buried for ages.

A hair, however, which has been very forcibly extended, will not return to quite its original length, but will remain a certain degree longer than it was previous to the extension. A hair may be extended a third of its length without breaking; elongated a fifth, it remains a seventeenth longer than it was before ; it continues a tenth longer after having been extended a fourth, and a sixth only after having been drawn out as much as possible.

Hairs, when they are dry, become electrical by rubbing, and emit sparks: this is well known with respect to the coat of the cat, and Eble has observed the same thing to occur in man.

Hairs are also eminently hygroscopic, and imbibe moisture from the air and from the skin, in consequence of which they lose their set or curl, and become flaccid and straight.

Nitrate of silver blackens the hair, a sulphuret of silver being formed, and it is of this ingredient that the majority of hair dyes are chiefly constituted. The concentrated mineral acids, especially the nitric, dissolve the hair, as does also caustic potash.

When heated, hairs take fire, and burn with a fuliginous flame, emitting the odour of bone, and leaving a residue of carbon. To dry distillation, they yield a quarter of their weight of carbon, which is difficult to incinerate, the products being empyreumatic oil, water charged with ammonia, and combustible gases, which comprise sulphureted hydrogen. The ashes contain oxide of iron, traces of oxide of manganese and silica, and of sulphate, phosphate, and carbonate of lime.

THE HAIRS OF DIFFERENT ANIMALS.

The precise structure of the hairs of different animals varies considerably : those of the mammalia resemble the hairs of man, or differ only in the degree of their development, as the whiskers of the carnivora and rodents, and manes and tails of horses, the bristles of


304 THE SOLID.

pigs, &c. : it is in these largely developed hairs that the structure can be best determined : thus, in the majority of them it is stated to be easy to detect the vessels and nerves of the papillae on which the bulb rests, and which penetrate into it: nerves have been detected by Eble in the cat,* by Rapp in the seal, porcupine, and many other animals, f and by Gerber in the pig. J

In the hairs of the musk-deer, there seems to be no separation of parts into scaly cortex, fibres and medulla, the entire hair being uniformly cellular.

In that of the sable, the fibrous portion is absent, and there is only scaly cortex and cellular medulla.

In the hairs of most rodents, the medulla is divided by dissepiments, and in other animals, as the sable, it is composed of large and distinct cells.

The hairs of the mouse, bat, and martin, are branched or knotted.

In the spines of the porcupine and hedge-hog, the inner bark penetrates in longitudinal bands into the cavity of the medullary canal, and thus divides the medulla itself into incomplete segments ; the transverse view of such spines represent a starred or rayed figure.

In birds, hairs are replaced by feathers, which are to be regarded as modified hairs.

THE USES OF HAIR.

The uses of hair are manifold.

In certain situations, as on the head, it is to be regarded as an ornament.

In other localities, as on the cheeks and chin, it imparts character and expression to the face.

In others again, as on the pubis and about the genital organs, it serves the purpose of concealment.

The general use of hair, wherever encountered, it being a nonconductor of caloric, is to preserve the warmth of the system.

Those situated at the entrance of the nares and meatus auditorius externus, are placed there to prevent the entrance of foreign bodies, insects, &c.

It is difficult to assign any use to the hairs of the axillae.

It is very probable that hairs have other uses, and that they exert some influence in regulating the electric condition of the body.

  • Von den Haaren, t. 11. p. 19. f Verrichtangen desfreuften Nervenpaares, p. 13.

J Allgemeine Anatomie, p. 79.


HAIK. 305

HAIR. [Plate LXX., fig. 4, represents transverse sections of the human hair.

Transverse sections of the hair, sufficiently thin to show the cellular structure, are somewhat difficult to make. When an instrument can be obtained, such as is used for making thin sections of wood, they can be prepared by taking a number of hairs, and gluing them together by means of some adhesive material, so as to form a solid mass. This bundle is then placed in the machine, properly wedged, and the transverse sections readily made.

Another method, is to puncture a cork with a fine needle, and insert or drive hairs in it ; when a sufficient number of hairs have been thus introduced, thin sections of the cork may be made with a sharp scalpel or razor. In these sections will be found some of the hairs cut transversely, and sufficiently thin to show their structure.

Sections of the beard may be obtained by repeating the operation of shaving a couple of hours after the beard was first cut ; on the razor will be found minute points of hair. Some of these, when separated and spread out with the needle, will exhibit transverse, others longitudinal sections.

When these are sufficiently thin to show their structure, they should be mounted dry ; but if too thick to show well in this condition, they may be rendered more transparent by being mounted in balsam.

The hairs of different animals present great varieties of structure, and their study will be found replete with interest.]

20


306 THE SOLIDS,

Article XIV. — Cartilages

Cartilages are among the most solid structures entering into the constitution of the animal organization; they are, however, not less remarkable for their elasticity and flexibility than for their solidity.

The essential element of the several fluids and solids hitherto described in the course of this work, we have seen to be cells: this cellular composition is exhibited in a high degree by cartilages.

The texture and colour of the cartilaginous tissue varies considerably : it presents either a white or bluish-white semi-transparent and homogeneous appearance, or it is yellow, and exhibits a fibrous texture.

These differences of texture and of colour indicate a difference of structure, upon which a division of cartilages into the true and fibrocartilages has been based.

TRUE CARTILAGES.

True cartilages consist of cells, contained in cavities, which are themselves formed in a solid and hyaline inter-cellular substance.

They comprise all those cartilages which cover the articular extremities of the bones (that of the glenoid fossa and of the head of the inferior maxilla alone excepted), the cartilages of the entire respiratory apparatus (with the exception of the epiglottis and the cuneiform cartilages), those cartilages which are to a considerable extent free and independent, and which have been denominated figured cartilages, as those of the ribs, the ensiform cartilage ; the trochlea of the eye, the nasal cartilages, and the Corpuscula triticea in the lateral hyo-thyroid ligaments. (See Plate XXX. figs. 1 and 2.)

The true cartilages are distinguished from the fibro-cartilages by their bluish and transparent aspect.

Structure of True Cartilages.

True cartilages consist, as already mentioned, of hyaline matrix, cavities, and cells; each of these constituents will be described in succession.

Hyaline Matrix. — The inter-cellular substance, or hyaline matrix, although it does not usually present any distinct traces of organization, yet contains, scattered through it, numerous granules of different sizes, and many of which are to be regarded as the cytoblasts from which new cells are continually being developed.


CARTILAGES. 307

The amount of this inter-cellular substance varies in different cartilages, and is greater in fully-developed than in very young cartilage.

Cavities. — The cavities of true cartilages vary both in size and form; in shape they are irregular, although for the most part elongated.

They are, in most cases, to be regarded as simple excavations or fossae in the hyaline matrix; in others, however, it would appear from the observations of Henle,* Bruns,f and Schwann, J that they are lined by a distinct membrane, and which is indicated by a double contour, by the difficulty experienced in setting free the contained cells, and by the fact that, by boiling, the inter-cellular substance is dissolved, while the cavities remain as distinct corpuscles.

Such cavities would stand in the relation of parent cells to those which they include.

Cells. — The cells of cartilages are very different from those occurring elsewhere in the animal organization; they are distinct in their form and in the character of their contents.

Cartilage cells, like the cavities in which they are enclosed, are irregular in size and shape; they are, however, generally elongated, sometimes flattened and compressed; at others, they are perfectly spherical : these several shapes depend upon the degree of pressure to which the cells are subject, and which is greatest at the free margins of the cartilages where the compressed form occurs, and least in the centre where the spherical cells are chiefly encountered. Each cell contains a nucleus, which is either smooth or granular; it includes also very generally one or more shining and globular bodies of an oleaginous or fatty nature, and which, in many cases, are to be regarded as transformed nuclei.

The cells usually lie as it were scattered irregularly throughout the inter-cellular substance ; in some cases, however, they are arranged in definite order; thus, in the condensed margin of all the true cartilages the cells are compressed, and lie with their long axes disposed parallel to the surface. (See Plate XXX. fig. 1.) Again, in the ribs, they radiate in straight lines from the centre towards the circumference: this disposition of them accounts for the fibrous fracture which they exhibit when broken across, as also for the fact of their being divisible into thin transverse layers. The linear arrangement of the cells in the fully-developed cartilages of the ribs is very frequently not perceptible.

In very thin cartilaginous laminae, as those forming the alae of the nose, the difference in the form of the central and peripheral cells does not exist, the entire inter-cellular substance being filled with small and rounded cells.

  • Anal. Gen., vol. vii. p. 364. -f Allg. Anat., p. 215. \ Mikrosk. Untersuch


The cells usually occur singly in the hyaline matrix; they are, however, frequently encountered in groups of two, three, or four cells, each of which is distinct, and describes a more or less regular segment of a circle: this disposition of the cells is connected with their mode of multiplication, as will be seen hereafter.

Again, groups of secondary cells sometimes occur, especially in the inter-vertebral fibro-cartilages, included in the membrane of the primary or parent cell. (See Plate XXXI.)

Moreover, Henle* has noticed a peculiar arrangement of the cells of the cartilages which cover the articulating surfaces of the larger bones. On the free surface, the cells are as in most cartilages small, flattened, and disposed horizontally; the deeper seated cells become larger and longer; their axes, on the contrary, being directed either vertically or obliquely to the surface ; sometimes also the cells, although separated by distinct intervals, are arranged the one above the other in such a manner as that the superior appears to be a continuation of the inferior; at others, an inferior cell appears to divide into two others, placed above it, and thus represents a bifurcation. Henle also states, that he has seen not unfrequently the outline of a cavity prolonged from one longitudinal series of cells to a neighbouring series. It is very possible, Henle goes on to observe, that these cavities form part of a system of elongated canals, which, taking an undulous course, and sometimes bifurcating, traverse the cartilage from its inferior to its superior surface, and which, when one makes a section, are divided into tw r o portions, the one remaining in one segment, the other in the other segment. This structure, he proceeds to remark, explains sufficiently why articular cartilages exhibit a fibrous fracture, and why the earlier observers believed them to be composed of fibres which ran perpendicularly to the thickness.

This ingenious notion of Henle, although it serves to account for some hitherto unexplained phenomena connected with the articular cartilages, is yet of very doubtful application even to them, and certainly no such arrangement of the cells and cavities as that just described belongs to the majority of true cartilages, or to any of the fibro-cartilages.

NSar the surface, the articular cartilages are more laminated, and may be separated into thin lamellae.

  • Anat. Gen., vol. vii. p. 366.


CARTILAGES. 309

In the smaller articular cartilages, the number of cavities and cells is more considerable, and the superficial layer of cells is not so well marked: the peripheral cells are small indeed, but for the most part rounded; a few are found in the neighbourhood of the bone, of an elliptical figure, but the middle layer presents circular cavities, with cells which are either single or multiple.

Nuclei. — The nuclei contained in cartilage cells are mostly granular, but sometimes present a smooth aspect, and then are scarcely to be discriminated from particles of oil or fat: in form they are sometimes rounded, but in general they are irregular in shape, and follow more or less closely the contour of the cells in which they are enclosed; they also frequently enclose a nucleolus.

Usually but a single nucleus is contained in each cell; occasionally, however, two, three, and even several are included within it; and sometimes it happens that one or more of these is invested by a distinct cell-membrane. (See Plate XXXI.)

The cells also include, as already remarked, particles of oil of a globular form and of a shining aspect; it has been suggested that these may probably in some cases be transformed nuclei.

The distinction of cartilages into true and fibro-cartilages, although useful for the purposes of classification, is to some extent artificial; since, on the one hand, some of the true cartilages, as old age approaches, become converted into fibro-cartilage, and on the other, the fibro-cartilages themselves, in the early period of their development, do not contain fibres, the cellular substance being hyaline, and identical with that of true cartilages.

The conversion of hyaline cartilage into fibro-cartilage has been observed to occur only in those cartilages which are subject to become ossified, as those of the ribs, the thyroid, &c.

Where ligaments are inserted* into true cartilaginous tissue, this in the neighbourhood of such insertion always exhibits a fibrous structure, in consequence of the fibres of the ligament penetrating into the inter-cellular substance. These fibres are of a nature totally distinct from proper cartilage fibres, as will be seen hereafter.

FIBRO-CARTILAGES.

Fibro-cartilages differ chiefly from true or hyaline cartilages, in that the homogeneous inter-cellular substance is replaced in them by fibres endowed with elasticity ; a transformation of structure of which we have seen that certain of the true cartilages are susceptible. (See Plate XXXI.)


The fibro-cartilages include those of the articulations which are united by synchondrosis, as the intervertebral cartilages, and that of the symphysis pubis; the epiglottis and the cuneiform cartilages; the articulating cartilages of the glenoid cavity, and of the head of the superior maxillary-bone; the inter-articular cartilage of the sternoclavicular articulation; the cartilages of the ear, of the Eustachian tube, of Santorini, and those of Wrisberg.

There are, however, other differences besides the structural one alluded to; thus, fibro-cartilages are more opaque than the true, are of yellow colour more or less deep, and are endowed with a higher degree of elasticity and flexibility.

The fibres do not follow the same distribution in every fibrocartilage : thus, in the tube of Eustachius, in the symphysis pubis, in the inter-articular cartilage of the sterno-clavicular articulation, in those of the tempero-maxillary articulation they are placed nearly parallel to each other; in the inter- vertebral cartilages, they ascend vertically from one osseous surface to the other; in the cartilages of the epiglottis and ear, they are curved and interlacing.

In the outer part of each inter- vertebral cartilage, the fibres form a distinct and compact stratum of a yellow colour, no cartilage cells in that situation intervening between them; the number of fibres, however, gradually diminishes towards the centre of the cartilage, which at the same time becomes less and less dense and firm, until at length in the very axis it is semi-fluid.

The cells of fibro-cartilages do not differ very materially in form and structure from those of true cartilages ; they usually, however, contain more fat, are more readily separable from the fibrous base in which they are lodged, and oftener encountered in the condition of parent cells.

The cells of the inter-vertebral cartilages and of the epiglottis present some interesting forms and modifications : thus, the cells which are situated in the harder parts of those cartilages are, on a vertical section, seen to be narrow and much elongated; while many of those imbedded in their soft and central parts are large and perfectly globular; many others of these, again, are in the condition of parent cells, and enclose either numerous nuclei or else many perfectly-formed secondary cells ; lastly, cells occasionally present themselves made up of concentric vesicles enclosed one within the other. Groups of adherent nuclei are also frequently met with deprived of an investing membrane. For representations of these several forms of cells, see the figures.


CARTILAGES. 311

Henle* describes as occurring in the epiglottis certain large, spherical, or oval cells, presenting in their interior an oblong cavity, from which proceed little branched tubes, which extend in all directions, even to the surface of the cells. These cells would appear to have some analogy with the osseous corpuscles. I have made diligent search for them in the epiglottis, but hitherto have failed to meet with them.

The fibro-cartilages are not soluble to the same extent in boiling water as the true, which are almost entirely so, and therefore yield less chondrine or jelly. The cells of these cartilages also resist the action of the water for a longer period than the inter-cellular substance, f

NUTRITION OF CARTILAGE.

Cartilages are among the number of non-vascular substances — that is, they do not, in general, receive into their own tissue distinct blood-vessels, but derive their nourishment from those which are distributed to the parts adjacent to them.

Thus, the articular cartilages are supplied with nutriment from the vessels which are so freely distributed to the extremities of the bones; in young children, and sometimes even in adults, the synovial membrane which covers the free surfaces of the cartilages also carries vessels which assist in their nourishment.

The independent or figured cartilages, as the ribs, &c, are surrounded by a membrane, composed of condensed cellular tissue, called the perichondrium : in this membrane the vessels which afford nutriment to the enclosed cartilages ramify. The ribs, moreover, contain grooves or canals, which, commencing on the inner edge of the rib, first run towards the centre, and then continue to pass forwards for some distance : these canals also contain blood-vessels.

In the centre of ribs about to ossify, a distinct medullary canal, containing blood-vessels in abundance, is clearly perceptible.

Vessels are also contained in the fatty masses enclosed in some of the joints, and called the glands of Havers ; from these the adjacent cartilages doubtless imbibe a portion of nutrient plasma.

Among fibro-cartilages, the synchondroses are stated to receive vessels. Nerves have not, as yet, been discovered in cartilages, which may be irritated for any length of time without the slightest pain being occasioned.

  • Anal. Gtn., vol. vii. p. 370.

f Meckauer (Carlilag. Slructura, 1836,) appears to have been the first to give, under the direction of Purkinje, a complete and accurate description of the cartilages of the human body.

During ossification, between the cartilage to be converted into bone and that which is to remain as the articular cartilage, a layer of vessels passes, which, as the ossification advances, gradually retire, and wholly disappear soon after birth.

As cartilages do not contain vessels, they are not subject to those disorders which depend upon errors of the circulation; that is, they are not liable to inflammation and its consequences. Ulceration of cartilages is indeed described by writers ; but this term is wanting in accuracy when applied to the erosion of which cartilages are susceptible, and which is effected not through any operation occurring in the cartilage itself, but through the action of vessels which, proceeding from the synovial membrane, dip down into the cartilage, and occasion its partial absorption. For the same reason, cartilages do not readily become atrophied by pressure : thus, when an aneurism destroys the bodies of the vertebrae, the inter-vertebral cartilages are not at the same time removed, but resist for a long period the continued compression to which they are subject.

There is, however, one description of cartilage in which bloodvessels regularly appear, viz: cartilages of ossification, in which may be included the costal and' thyroid cartilages, their presence proceeding and accompanying the process of the formation of bone.

Cartilages, like all the extravascular tissues, imbibe fluid readily: thus, when immersed in a coloured solution, they assume the tint of the liquid in which they are placed. In jaundice, according to Bichat,* they present a greenish yellow tint, from the imbibition of a portion of the bile with which, in this disorder, the system is so pregnant.

GROWTH AND DEVELOPMENT OF CARTILAGES.

Cartilages, as already observed, consist of cells imbedded in a hyaline or fibrous base. In considering, then, the development of cartilages, the growth of both the cells and the inter-cellular substance must be discussed.

We will first describe the multiplication of cartilage cells.

The Cells. — Cartilage cells are multiplied in two ways.

1st. By the division of a single cell into two or more parts, each of

which becomes, when the separation is completely effected, a distinct

cell. The reality of this method of increase in the number of cells

will become evident, on the attentive examination of almost any thin

  • Anal. Gen.,t. iii. p. 192.


CARTILAGES. 313

section of cartilage, in the cells of which, but especially in those placed near the natural border, the several stages of their division may be clearly and satisfactorily recognised. (See Plate XXX.)

2d. By the development of cytoblasts either in the inter-cellular substance, or else in parent cells. This mode of increase is a true reproduction, new cells being continually formed and developed. The first process of multiplication is of a nature totally distinct from reproduction ; for although by it the cells are multiplied, no new ones are developed. There is the same difference between the two forms of cells, that having its origin in the division of a single cell, and that developed from a cytoblast, as there is between a slip and a seed. (See Plates XXX. and XXXI.)

The parent or primary cells, filled with the second or even the third generation of new cells, may be detected in abundance in almost any cartilage, but especially in the inter-vertebral cartilages. It is worthy of notice, that the parent cells are usually situated near the centre of each cartilage, while the single cells, in which the process of division is best seen, are mostly found outside these. From this arrangement we may infer that the deeper-seated cells are older than those of the circumference. Whether the latter are derived from the former, or whether they are formed on the external margin of the cartilage, it is not easy to decide ; it is most probable, however, that, from the circumstance that the parent cells are principally found in the centre of the thicker cartilages, and that it is in this situation that ossification commences, that the second conjecture is the correct one.

It is a singular fact, that the development of cartilage cells may be as readily followed out in old cartilages as in young, numbers of cells in process of division and in the stage of parent cells being readily distinguished in each. As after maturity cartilages do not undergo any increase in size, and as from the preceding observations it would appear that new cells are continually being evolved, it must be presumed that the very old cells are absorbed and their place supplied by the younger ones.

In the multiplication of cartilage cells by division, a correspondence may be traced between cartilages and many of the lower tribes of animals and vegetables, especially with the majority of the algae ; and in the development of secondary cells in parent cells, they exhibit a still closer analogy with certain algae of the genera Hcematococcus and Mycrocyslis, the cells of some of the species of which it would be impossible to distinguish from the isolated cartilage corpuscles of the epiglottis and inter-vertebral cartilages.

In these methods of multiplication, cartilage cells would appear almost to stand alone in the animal economy: thus, it is certain that the red blood corpuscles, epithelial cells, and their various modifications into epidermis, nails, pigment cells, and hairs, are not multiplied either by division or by the development of secondary, enclosed in primary or parent cells.

The analogy existing between the cells of cartilages and those of certain algas has been noticed by Dr. Carpenter, in the third edition of his "Principles of Human Physiology."

The Inter -cellular Substance. — Very young cartilages, and also the smaller ones of adults, are constituted almost entirely of cells, with but little admixture of inter-cellular substance. As, however, these young cartilages grow in size, the relative amount of this substance increases, and the space between the cells becomes greater.

The augmentation of the inter-cellular substance takes place principally by a deposit of new layers on the exterior surface during the period of the development of cartilages; this mode of increase is proved by their separation after long-continued maceration into distinct laminae.

A second mode of increase of the inter-cellular substance has been stated to exist by Henle,* principally in the cartilages of ossification, and under no circumstances in the fibro- cartilages, viz : by the thickening of the walls of the cells, which become confounded with or melted down into the inter-cellular substance, the cavity in which the cells are lodged being diminished, or this also augmenting at the same time. The proofs adduced in favour of this method of increase are not convincing.

It has already been stated that in the true cartilages which are subject to ossification, fibres appear; these fibres, as well as the analogous ones of fibro-cartilages, are probably of a nature wholly distinct from those of ordinary cellular tissue, and which have their origin in cells ; under no circumstance can either cells or nuclei be discovered in the fibres of cartilages.

Cartilage is not capable of regeneration: when it has been fractured, the union of the surfaces is very incomplete, and principally by means of cellular tissue.

The formation of cartilage almost invariably precedes the development of bone, of which we shall shortly have to speak more particularly in the Chapter on Bone.

  • Anat. Gen., vol. vii. p. 376.


CARTILAGES. 315

Masses of cartilage are also occasionally produced upon the external surface of the synovial membrane of joints; these are at first peduncated, but at length cease to have any connexion with the organization, and move freely about in the cavity of the joints.

Occasionally, though rarely, cartilage is developed in the cellular tissue of glands, forming a solid tumour, which was first described by Muller, under the name of Enchondro?na b and of which I recently had the pleasure of receiving a very excellent example from Dr. Letheby.

USES OF CARTILAGES.

The uses of cartilages are of a mechanical nature, depending upon certain physical properties.

Thus, we find them to be situated in localities where solidity is required in combination with flexibility and elasticity.

In the larynx, the flexibility and elasticity of cartilages assists in the modulation of the voice.

In the nose, so liable to injury, their flexibility often allows this organ to sustain severe blows without detriment.

The articular cartilages protect the bones from injury to which they would be otherwise so subject in the sudden and violent exertions of the body, as in jumping, on account of their solid and unyielding nature.

The inter-vertebral cartilages are exceedingly elastic and flexible, and permit the free movement of the spinal column in almost any direction, and which is so necessary in the execution of the various motions of the body.

The articulations united by synchondrosis, as that of the pubis, are remarkable for their strength, although at the same time it admits a slight degree of extension and compression.

Lastly, the epiglottis is enabled to preserve the erect position so essential to the maintenance of life in consequence of its exceeding elasticity.


CARTILAGE.

[For an elaborate and complete account of "the intimate structure of articular cartilage," see a paper on that subject, with plates, by Jos. Leidy, M. D., of Philadelphia, published in vol. xvii. (new series) of the American Journal of Medical Sciences, pp. 277-294.

The development of cartilage is of course best studied in the fetal subject.

In the adult, cartilage may be examined in their vertical sections. Articular cartilage is easily separated from bone, after slight immersion in acid.

Preparations of cartilage should be preserved in cells with fluid.

Plate LXX., fig. 5, Cartilage from the finger-joint, showing terminal loopings of vessels.]


BONE. 317

Article XV. — Bone

The next tissue to be considered is the osseous.

Bones are divided after their form into long, flat, and irregular: long bones consist of a body or shaft termed diaphysis, hollowed out in the centre into the medullary canal, and of two extremities called Epiphyses, and which in early life are distinct from the shaft; each long bone, moreover, is made up of two modifications of bony structure, the cancellous and the tabular; the former is loose and reticular, the latter hard and compact: of the one, the great bulk of the epiphyses are constituted; of the other, the diaphysis is chiefly formed: in flat and irregular bones, the medullary canal is wanting ; the first consist of an inner and outer table of compact bony tissue, enclosing a thin plate of cancellous structure, termed Diploce, and the latter are composed principally of cancelli, enclosed in thin and irregular osseous laminae.

STRUCTURE OF BONES.

The two elements into which all bones resolve themselves are osseous corpuscles and laminae ; the latter, according to the plan of their arrangement and development, give rise to the cancelli, medullary canals, and plates of which bones are constituted.

Cancellous Structure.

The cancellous structure of bone is made up of thin and inosculating plates of bony matter, which enclose spaces between them, and all of which freely communicate with each other : these spaces are called medullary cells. Each plate is also compounded of several laminae, in the intervals between which a few bone corpuscles exist.

The fact of the free communication of the medullary cells is proved by the two following experiments :

Thus, when mercury is poured into a hole made in the exremity of a long bone, or on the surface of a flat or short one, it will traverse all the medullary cells, and escape by the apertures which exist naturally on the exterior of bones.

Again, if a bone be cut through at one of its extremities, the natural openings on its surface being at the same time closed, and if then the bone be exposed to the action of heat, all the marrow will escape slowly by the cut extremity.*

The spaces described by the medullary cells are irregular in size and form, those which are first developed being smaller than those of older formation (see Plate XXXIV. fig. 3, 4) : they are usually of an elongated shape, their long axes being parallel to that of the bone itself: when viewed transversely, they are seen to be more or less rounded, but irregular in outline : it is in the transverse sections that the bone cells and lamellae are best seen.

Medullary cells in the recent state are filled with fat vesicles, with blood-vessels, and with granular nucleated cells analogous to those of epithelium: these last occur in considerable quantities in the cancelli, and especially in those of fetal bones, in which the fat vesicles are for the most part absent. (See Plate XXX. fig. 4.)

They inosculate freely with the medullary canals situated in the outer and compact plates of bone.

Canalicular Structure.

The compact tissue of bones is traversed by canals, which have been termed medullary from the fact of their being in communication in the long bones with the great central medullary cavity, and from the circumstance of their being partly occupied with medullary matter. They are also called Haversian, after their discoverer.

These canals are situated between the laminae of which bone is composed, and take a course in the long bones, in which they are best seen, parallel to their axes, being also joined together by short transverse branches : they thus form a net- work of tubes analogous to that exhibited by the minute vessels which they convey and protect; the form and sizes of the meshes vary: in the long bones they are elongated. (See Plate XXXII. fig. 4.)

They communicate, in the long bones, with the medullary cavity, dilating into cells or vesicles, from which a short tube proceeds previous to their entrance into it; they also open upon the external surface of all bones by somewhat expanded apertures, and inosculate freely with the medullary cells.

Medullary canals are not all of equal diameter throughout the compact tissue of a bone ; those situated between the external plates are two or three times smaller than those which are placed more internally. (See Plate XXXII. fig. 1.)

  • Bichat, Anatomie Generate, t. 111. p. 25.


BONE. 319

In a transverse section, the canals are seen to be either circular, oval, or rarely angular.

In the flat bones, the comse of the medullary canals is more irregular than in the long bones; in the parietal bones they proceed diverging from the parietal protuberance towards the margins of the bone; and in the frontal from the supra orbitar ridge towards the coronal suture.

In the long bones, near their extremities and in the vicinity of the articular cartilage, these canals end in blind or csecal extremities, a single canal passing up into each of the prominences, into a number of which the articular surface of bone is elevated.*

It is these canals, which impart the striated structure presented by bone, and which is visible to the unassisted eye; in longitudinal sections, they are frequently cut through, and their cavities exposed.

The contents of medullary canals are similar to those of the medullary cells, of which they are to be regarded as a modification, there being an insensible transition from the one to the other.

Drs. Todd and Bowman recognise two forms of Haversian canals, one of which carries veins, the other arteries, a single vessel being distributed to each ; those canals which contain the veins are stated to be larger than those which convey the arteries, and to be dilated into a pouch or sinus at the situation where two or more canals unite to form a single larger tube.

Lame lice.

The more essential constituents of true and fully developed bone are, as already observed, lamellae and bone cells; the medullary cells and canals just described are merely definite spaces existing between the lamellae, the arrangement and ultimate structure of which we shall in the next place proceed to notice.

It is principally by the successive development of new lamellae that bones increase in diameter; these are usually deposited in the direction of the axis of the bone; if, therefore, a transverse section of a long bone be made and examined with the microscope, the lamellae will be seen to be arranged as follows: First, several layers will be observed to pass entirely round the bone ; secondly, others will be noticed encircling each Haversian canal; and lastly, irregular and incomplete lamellae occupy the angular spaces intervening between the sets of lamellae concentrically disposed around each canal. (See Plate XXXII. figs. 1, 2, 3.)

  • See Med. Chir. Rev. No. x. p. 528.


The number of layers which pass interruptedly around the bone are not very numerous, being generally less than twelve; the amount of those which encircle each Haversian canal varies from two or three to upwards of twelve, the smallest number of lamellae usually appertaining to the smallest canal. (See Plate XXXII. fig. 1.)

Examined with an object-glass of the fourth of an inch focus, the lamella, after the separation of its earthy matter by means of dilute hydrochloric acid, exhibits a delicate structure, the precise nature of which it is not easy to determine ; its surface will be seen to be marked out into innumerable lozenge-shaped spaces, one side of each of which is concealed by a dark shadow, and the divisions between which are without shadow. (See Plate XXXIII. fig. 4.)

This interesting structure was first distinctly pointed out by Dr. Sharpey,* who conceives that it arises from the crossing and union of fibres; these, however, cannot be traced out and displayed as separate fibres, owing, it is presumed, to their being united or fused together at the points where they cross each other; it sometimes happens, however, that at the torn edge of a lamella a short projecting process may be seen, which presents much the aspect of a true fibre.f

The appearance presented by a lamella thus figured might be compared to the engine-turned case of a watch, and it might also be conceived that it was produced by the union of a number of diamondshaped cells, and not by the crossing of fibres.

One argument in favour of the fibrous constitution of the lamellae

O

may be derived from the fact that the cancelli of bone in process of development clearly exhibit a fibrous structure.

Cross sections of the lamellae may also sometimes be observed to be marked with short and radiating lines, which most probably depend upon the structure already noticed.

The osseous lamellae are likewise perforated necessarily with numerous minute apertures occasioned by the canaliculi of the bone cells, and which, when seen with a low power, appear like so many

  • Quain's Anatomy, 5th edition, part ii. p. cxlii.

f It would appear to he prohahle, from the following quotation, that Henle had seen the structure ahove described. " The lamellae examined on their flat side have appeared to me to he generally hyaline or finely dotted, but sometimes also fibrous ; the fibres are either pale, and as thougli composed of grains, or obscure and rugged; one never succeeds in isolating them for a certain space, because they are branched, interwoven, and, in a word, perfectly identical with the fibres of fibro-cartilages."


BONE. 321

small dots ; they contain, also, scattered throughout their substance, multitudes of granules of earthy matter.

The only really necessary constituents of bone would appear to be the cellular tissue and earthy matter. The combination of these two forms bone in its simplest condition. The medullary cells, Haversian canals, and bone cells, are connected only with the growth and nutrition of bone, and occur seldom, except where the size of the bony formation renders their presence necessary for its growth and support.

Bone Cells.

Distributed throughout the cancellous and compact portions of bone, cells of a peculiar structure occur in considerable quantities.

Concerning the nature of these cells, much difference of opinion prevails; by some they are described as mere vacuities existing in the tissue of the bone; by others as hollow cells, as nuclei of cells, and as true nucleated corpuscles. That the bone cells take thenorigin in nucleated cells, cannot be doubted.

The circumstances which have given rise to the notion of their being mere vacancies or lacunae, are the passage of fluids through them, their infiltration with solid matter, and the optical appearances sometimes presented by them. All these circumstances admit, however, of explanation on the supposition of their corpuscular origin.

That they are derived from granular cells may be proved, it seems to me, by the study of the development of bone, they being in growing bones first traceable as nucleated corpuscles, a condition to which they may be again reduced in an adult bone by the removal of the earthy matter. This appearance is best seen in the large bone cells of the Siren, Proteus, or Menobranchus.

The bone cells, which are very numerous, are situated between the osseous laminae already described, and by which they are compressed; they thus present in all sections of bone an elongated or flattened form, and in transverse cuttings those facing the Haversian canals appear not merely elongated, but also slightly curved, the concavity of the arc being directed inwards towards the canals, and the convexity outwards in the contrary direction. (See Plate XXXII. Jigs. 1, 2.)

When viewed as transparent objects, they appear black, and when as opaque, they are of a pearly whiteness.

From the margins of each bone cell proceed a number of branched canals, which, passing through the lamellae situated on either side of the cell, inosculate freely with the canaliculi given off by the bone cells of the contiguous lamellae (see Plate XXXII. fig. 3) ; this process of inosculation being frequently repeated between the cells of each lamella, a communication is thus established between the medullary cavity on which the canaliculi of the first series of cells opens, the Haversian canals, and the external surface of the bone. The reality of this communication may be attested, by applying a drop of oil of turpentine to a section of dry bone placed beneath the microscope, when the passage of the fluid through the bone cells may be followed with the eye. This experiment was first suggested by Drs. Todd and Bowman.

The canaliculi of bone cells treated with acid usually disappear, the body of the cell alone remaining.

The size of the bone cell throughout the whole of that osseous ver tebrate series, stands in relation to that of the red blood disc ; and Mr. Quekett, who has instituted an inquiry into their form and size in a great variety of animals, has arrived at the conclusion that the class to which any animal belongs, whether that of Beasts, Birds, Reptiles, or Fishes, may be determined by the two particulars referred to. This discovery is likely to be especially useful in the determination of the true position in the' animal series of many fossil bones, which but for it, would have continued to be enveloped in uncertainty and conjecture.

In many osseous fishes, the bone cells appear to be wanting, they having merged into canaliculi, which are often of considerable size.

Marrow of Bones.

The medullary cavity of adult long bones, the medullary cells, and the larger medullary canals, all contain a loose cellular tissue, in the meshes of which a greater or less amount of marrow or fat cells is enclosed. (See Plate XXX. figs. 3, 4.)

In foetal and very young bones the fat vesicles are wanting in the three situations named, the place of fat being supplied by immense numbers of the small granular nucleated cells, which have already been referred to. (See Plate XXXIII. fig. 5.)

It has been stated that the medullary cavity, cells, and canals all communicate freely; the marrow therefore and its enclosing cellular tissue are every where continuous.

Periosteum. The external surface of all bones, with the exception of their artic


BONE. 323

ular extremities, is covered with a dense membrane composed of fibrous tissue, which is very rich in blood-vessels, and which is called the periosteum.

The internal surface of the medullary cavity, cells, and larger Haversian canals, is also lined by a vascular membrane much more delicate in structure, which may be regarded as an internal periosteum.

It is by means of the vessels which ramify through these membranes that the nourishment of the bone is secured.

Vessels of Bone.

Bones are richly supplied with blood-vessels, which penetrate every part of their structure.

Thus externally, branches, principally arterial, proceed from the periosteum, enter the numerous apertures of the Haversian canals, and, ramifying through these, form a capillary net-work; these external periosteal vessels may be seen with the unaided eye, extending into the bone like so many fine threads, on the cautious detachment of the periosteum.

Again, in the long bones, a large artery penetrates by an oblique canal situated at the junction of their upper' and middle thirds, into the medullary cavity, and sends branches upwards and downwards, which ramify on the membrane of the medulla or internal periosteum; some of these proceed onwards into the medullary cells, and others inosculate with the capillaries of the Haversian canals already referred to.

The flat and irregular bones are furnished not with a single vessel of large calibre, but with several of smaller size.

These larger arteries are accompanied by veins, whereby a portion of the venous blood is returned from the bone.

Breschet,* moreover, has described in the flat bones, and especially in those of the cranium, a system of osseous canals, which contain only veins, and which are furnished with valves, which is not the case with the other veins of bones.

The walls of these canals, which ramify after the manner of vessels, are pierced with apertures, by which they receive small capillaries: they traverse principally the spongy portion of bones, afterwards they pass through the compact part, and finally terminate on the external surface of the bone.

  • N. A. N. C. xxiii. P. i. p. 361.; Recherches Anat. Physwlog. el Pat. sur le Systeme Veineux, Paris, 1829. fol.


324


THE SOLIDS


These canals are best seen in the flat bones of the cranium, which should be dried, and the outer table of compact substance removed. Lymphatics have been observed in some few instances in bone.

Nerves of Bone.

Nerves have not hitherto been satisfactorily traced into bones; nevertheless, the great pain experienced in diseased conditions of them proves incontestably the existence of nervous fibrillee.

GROWTH AND DEVELOPMENT OF BONE.

Growth of Bone. — The situations in which the chief increase of bone occurs are commonly stated to have been accurately determined by means of the different madder experiments instituted by numerous observers.

If an animal be fed for a short time with the root of madder, its bones will become tinged with the colouring matter of that plant, between which and the phosphate of lime of the bone a great affinity exists.

On a close examination of sections of a growing long bone it will be observed, however, that the tissue of the bone is not uniformly coloured, but that in a transverse cutting the colour is principally situated in the outer part. The same fact is shown also in longitudinal sections, which, however, if they embrace the entire length of the bone, will also be observed to be tinged with the colouring matter towards either extremity.

Again, if a magnifying glass be applied to a thin transverse section of the growing bone of an animal fed upon madder, each Haversian canal will be seen to be surrounded by its ring of colour. For this beautiful illustration of the effects of madder we are indebted to Mr. Tomes. (Plate XXXIII. fig. 6.)

These several observations have been presumed to prove that bones increase in length principally by additions of new matter to their extremities, and in breadth by the deposition of new laminae of bone on their outer surface, as well as by the formation of fresh lamellae in each Haversian canal, which last grow and expand in size simultaneously with the laminae placed external to them after their first formation.

Now, although it is very probable that bones increase in diameter to a great extent by the addition of new matter on the external surface, and although it is quite certain that they become elongated by


BONE. 325

the formation of bony matter at their extremities, it appears to be most clear that we are not justified in coming to any such conclusion from the results of the experiments with madder. All that these celebrated experiments really seem to prove is, that bones in contact with blood-vessels containing the colouring matter of madder, readily imbibe and retain that principle in common with the liquor sanguinis.

The bones of old animals are coloured with much more difficulty than those of young; a few hours in very young animals being sufficient to ensure their colouration.

Development of Bone. — We come now to consider the exact process of the development of bone.

Bone is developed either in membrane or in cartilage ; when in the former, it may be termed intra-membranous, and when in the latter, intra-cartilaginous ossification.

Intra-membranous Form of Ossification. — We will consider, first, the intra-membranous form of ossification. Dr. Nesbitt* was the first to distinguish between the two types of ossification. More recently Dr. Sharpeyf has described clearly and satisfactorily the steps of the intra-membranous development. This form he considers to belong to certain flat bones of the cranium, as the parietal and portions of the frontal and occipital bones, as well as to the outer surfaces of the long bones.

The first perceptible ossification of the parietal bone, which may be selected as one of the best examples of this form of osseous development, consists of a net-work of spicula of bone, the outermost of which radiate in lines towards the circumference, and are connected by short transverse branches. (See Plate XXXIII. figs. 1, 2.)

As the ossification proceeds, the first formed spicula, in the centre of the bone, become greatly increased in thickness, and the spaces between them much diminished in size; the ossification continues thus to spread and consolidate until the parietal meets the neighbouring bone, with which it is at length united by suture.

If, however, the microscope be brought to bear upon one of the newly-formed spicula before the entire bone has attained any considerable development, it will be seen that the ossific deposit takes place in the fibres of fibro- cellular tissue, intermingled with which numerous granular and nucleated cells occur; these fibres, which are disposed in bundles, invariably precede the deposition of bony matter, and mark out the course of the future spicula. (See Plate XXXII. fig- 3.)


  • Human Osteogony, Lond. 1736.

f Dr. Quain's Anatomy, edited by Mr. Quain and Dr. Sharpey, 5th edition.



The granular cells just noticed have been observed by Dr. Sharpey, who remarks upon their distribution in the direction of the future spiculse, and who considers that they are connected in some way or other with the process of ossification.

There can scarcely be a question but that they are the bone cells in a rudimentary state, their conversion into which it is not difficult to trace.

Now, it does not appear that cartilage is at all concerned in any one stage of the development of the parietal bone of the human embryo. In that of the sheep, and some other animals, a lamina or cartilage is present in connexion with the parietal bone ; but this takes no part in the process of ossification, but merely serves as a support to the newly-developed bone, and extends beneath the first-formed portion of it alone.

As the ossification advances still further, the interstices between the first-formed spicula become filled up, grooves appear on the surface of the bone; these radiate from the centre towards the circumference, and ultimately become converted into canals, which, being lined with a number of concentric laminae, at length constitute the complete Haversian canals. The bone is then completely formed.

Intra-cartilaginous Ossification. — It has, until recently, been supposed that the formation of bone always takes place in cartilage; this notion, as we have seen, is erroneous.

Ossification is also usually described as the conversion of cartilage into bone; this idea will be presently shown to be equally erroneous, and the fact demonstrated that the intra-cartilaginous ossification does not differ essentially from the intra-membranous form.

If the microscope be brought to bear upon a thin longitudinal section of an ossifying foetal bone, in connexion with its cartilaginous epiphysis, the following particulars will be noticed :

First, it will be observed that the cartilage cells in the neighbourhood of the bone, instead of being scattered irregularly throughout the intercellular substance, are arranged in several consecutive and alternating rows or files, the lowermost of which dip into and are surrounded by osseous cups and septa; that the cells forming the lower portion of the lowest tier are larger, and less compressed, than those which enter into the formation of the upper part of each lower series, and that they are separated from each other by distinct portions of inter-cellular


BONE. 327

substance. Secondly, it will be remarked that the extremities of the still soft bony spicula invade and extend into the spaces which intervene not merely between the rows of cells, but also between the individual cells, and further, that granular and probably cytoblastemic particles are deposited in this inter-cellular substance, particularly where this comes into contact with the cartilage cells themselves. (See Plate XXXIV. figs. 1. 4.)

As the process of ossification advances, the cell-wall of the cartilage cells becomes absorbed; granular corpuscles are next generated in the primary cancellus ; after which the nuclei of the cartilage cells (which are observed to become smaller, the deeper they lie in the bone) are removed by absorption; finally, the small septa intervening between the individual cartilage cells are removed, the larger medullary spaces being thus formed. (See Plate XXXIV. fig. 4.)

Furthermore, in these precursory and even in the older spicula, fibres analogous to those in which the spicula of the parietal bones are developed, may be abundantly detected.

Such is a brief sketch of the several steps of the intra-cartilaginous form of ossification.

Now, the process which we have just described, is constantly in progress ; cartilage cells on the one side are continually being developed in the epiphysis; they are also constantly marshalling themselves into rows or columns, the lowermost cells of which dip into the cancelli and become absorbed ; on the other side, the cancelli of the bone are continually invading the inter-cellular spaces of the cartilage.

It is thus that a bone grows in length. Each epiphysis of a long bone, however, after a time, becomes a centre of ossification; this proceeds to meet that of the shaft; a layer of cartilage usually, however, intervenes between the two, until the period of the full development of the osseous system, when this layer becomes absorbed, and the shaft and the epiphysis become consolidated by bony union. The first trace of ossification of the epiphysis in the human subject is usually apparent at about the ninth month.

We have now to ask ourselves the question, how does the bone increase in diameter? We have shown that it is generally considered, as proved by the madder experiments already referred to, that a long bone increases in breadth by the deposition of new lamellae at the circumference, as well as in the cavities of ihe medullary and Haversian canals; but we have seen also from what has been already said in reference to the different sizes of the external and internal Haversian canals and their mode of formation, that each of these canals is continually undergoing a process of expansion, and it is by this expansion that the chief increase of the diameter of a bone takes place. It was formerly supposed that a layer of cartilage existed in all growing bones on their external surfaces, but we now know that such is not the case, and that the new osseous deposit takes place in fibres. If it were necessary that a layer of cartilage should exist in the situation named, it would be equally requisite that it should be present in each medullary cell, and in each Haversian canal.

The small granular corpuscles already referred to as occurring in the cancelli of all bones, but especially in those of the foetus, it would thus appear are developed in considerable quantities at a very early period of the development of bone ; they are generally apparent in the third or fourth tier of the first formed and small cancelli, and while the nuclei of the cartilage cells yet exist. (See Plate XXXV. fig. 3.)

It will now be perceived that the intra-cartilaginous form of ossification is identical with the intra-membranous type in all essential particulars.

It will also readily be seen that this view of the process of ossification differs very considerably from the more recently expressed opinions on the subject ; those, for example, of Drs. Todd and Bowman, and of Mr. Tomes.

The authors of the "Physiological Anatomy" consider that the nuclei of the cartilage cells become developed ultimately into the bone cells.

There are many considerations which would lead to the conclusion that such a transformation is but little probable, the following of which may be referred to:

The formation of bone, independent of cartilage, as in the intramembranous type of ossification.

The small number of the cartilage cells, compared with the vast quantities of bone cells which exist in even a young bone.

The impossibility of explaining why the permanent cartilages should not, like the temporary, be constantly subject to ossification, since they are both organized in precisely the same manner.

The proof that cartilage cells have no further stage of development to pass through, manifested by the fact of the occurrence of parent cells in all cartilages, whether temporary or permanent.

The chief new points contained in Mr. Tomes's views* are the

  • See Art. " Osseous Tissue," Cyclop of Anatomy and Physiology.


ossification of the walls of the several cartilage cells which form each roll or column, and the conversion of a number of these, by the absorption of the contiguous walls of the cells into a single cavity or tube, which becomes filled with a granular blastema; this tube Mr. T. considers to be an Haversian canal, and its wall to constitute ultimately the outer lamina of such canal.

The arguments adduced in disproof of the opinion that the nuclei of the cartilage cells become converted into bone corpuscles, apply with equal force against the idea of the calcification of the walls of the cartilage cells.

Bone Cells. — Bone cells, then, according to the views of the author, are not transformed nuclei of cartilage corpuscles, but take their origin in distinct granular cells, which may be clearly seen in the growing spiculae of bone dispersed among the fibres in which the earthy matter of bone is first deposited, and which at length become entirely imbedded in the earthy deposition.

As, however, it is most probable that a development of bone cells and new laminae of bone are ever in progress even in adult bones, we should expect to encounter in the cancelli of bones of every age fibres of cellular tissue and granular cells; both these do occur in them, and especially the latter, which are met with in great numbers.

These granular nucleated cells are more numerous in foetal and young bones than in those of older formation ; in the former, indeed, they almost entirely fill up the cavities of the cancelli : in the latter, although they are still numerous, their place is supplied with fat vesicles, which are not present in the former.

It seems to me to be not improbable that two kinds of granular cells may exist in the medullary spaces, &c, one consisting of rudimentary bone cells, and the other connected with the elaboration of marrow, which occupies the medullary cavity, medullary cells, and larger Haversian canals.

It might be supposed that these granular cells were the white corpuscles of the blood escaped from the ruptured vessels, the red blood discs having been absorbed ; this notion is, however, disproved by the fact that many of them are much larger than the colourless corpuscles of the blood. (See Plate XXXIII. Jig. 5.)

The existence of a granular blastema in the cancelli, &c, of bones was first observed by Drs. Todd and Bowman,* who considered that it was concerned in the development of blood-vessels.

  • Physiological Anatomy, chap. v.


Presuming it to be proved that the bone cells are derived from true corpuscles, we have yet to decide whether we are to believe with Schwann,* that they are complete cells, and that the canaliculi are prolongations of the walls of these cells ; that, in fact, they possess a structure conformable with that of the stellate pigment cells of the skin of the frog, or of the lamina fusca of the eye ; whether we are to consider with Gerber,f Bruns,J and E. H. Mayer,§ that they are the nuclei of primitive elementary cells, and that the canaliculi are prolongations of these; whether, again, we are to regard them with Henle|| as the cavities of cells, the walls of which have become thickened, and the canaliculi of which proceed from the central cavity through the thickened walls of the cells, as do the porous canals of many vegetable cells; lastly, whether we are to believe, with Todd and Bowman, that the canaliculi proceed from the nucleus, which afterwards becomes absorbed, and that thus the lacuna is left.

That the first view is the correct one, and that the bone cells are to be regarded as complete corpuscles, the canaliculi of which are formed by the extension of the cell wall, is, I think, proved by watching the formation and development of bone cells in growing spiculae and by the action of dilute hydrochloric acid, which, by removing the earthy matter, allows the granular texture, which originally characterized them, to be again seen.

The last points left for consideration in reference to the development of bone are, the modes of formation of the medullary cavity, medullary cells, and Haversian canals.

Formation of Medullary Cavity. — Traversing the substance of each cartilaginous epiphysis, a number of large and branched canals may be seen in both transverse and longitudinal sections. (See Plate XXXV. figs. 1, 2.)

The majority of these proceed directly from the ossified part of the shaft in connexion with the epiphysis ; in this situation they are of larger size, and are also fewer in number, than they are higher up in the epiphysis, not exceeding usually five or six, but becoming multiplied, by the giving off of branches, to as many as fourteen or sixteen ; others, however, enter the epiphysis from the sides, near the junction of the bone and cartilage.

The interior of these canals is occupied with blood-vessels and

  • Mikroskopische Untersuchungen, pp. 35. 115.

f Allgemeine Anaiomie, p. 104. \Ibid. pp. 240. 252.

\ Miiller, Archie. 1841, p. 210. II Anal. Gen. t. vii. p. 409.


BONE. 331

with granular nucleated cells, precisely like those existing in the medullary cells of bone. (See Plate XXXV. fig. 3.)

The cartilage cells in a transverse section of the canals immediately surrounding their orifices are disposed in a rayed manner.

Having thus described the structure, contents, and distribution of these canals, we will next inquire their use. (See Plate XXXV. tig. 3.)

If a number of transverse sections be made, not merely of the cartilaginous epiphysis, but also of the bone in connexion with it, and if these be examined in the order of their removal, it will be observed, first, that in those sections which are made from the cartilaginous epiphysis most removed from the bone, the apertures of these canals are small and numerous (see Plate XXXV. fig. 1) ; second, that in the sections taken from the proximal end of the epiphysis the canals are fewer in number and their orifices larger (see Plate XXXV.) ; thirdly, that in other slices, which include a portion of both cartilage and bone, the latter always commences on the circumference of the section, proceeding gradually inwards, the portion of cartilage surrounding the canals in question being the last to become ossified (see Plate XXXV. figs. 2, 3) ; fourthly, in cuttings made below the cartilage and through the bone, spaces four or five in number, filled with granular cells corresponding in situation with the afore-described canals, will be observed; fifthly, in others carried still deeper into the bone, these several apertures will have coalesced into one large space — the rudimentary medullary cavity.

From these several particulars, I therefore infer that the canals in question are intimately connected with the formation of the medullary cavity ; and that the absorption of the cancelli situated between each of them is brought about by the vessels contained within them, aided also probably by the granular cells.

Were the canals merely destined to convey to the cartilage the nourishment necessary for its transformation into bone, it might be expected that they would serve as so many centres from which the ossification would proceed ; we have seen, however, that the cartilage in their immediate vicinity is the last to be removed, and its place supplied by bony cancelli.

Medullary Cells. — The primary cancelli are small, studded with granules, form closed cavities, and do not contain bone cells. (See Plate XXXIV. figs. 2, 3.) The secondary and larger cancelli are formed by the absorption of the numerous septa of the primary cancelli ; they do not form closed cavities, but communicate freely together, and contain bone cells imbedded in their parietes. (See Plate XXXIV. fig. 4.)*

Haversian Canals. — The Haversian canals are generally described as being formed by the filling up of certain of the medullary cells, in consequence of the successive deposition of new laminae of bony matter. It seems to me, however, to be very questionable whether they are formed in the manner indicated, and if so, such is assuredly not the general mode of their formation.

I am induced to take a different view of their formation, and consider they originate as follows :

The surface of all bones, whether long, flat, or irregular, is observed to be marked with numerous grooves of different sizes and depths. In the recent state, these are occupied with blood-vessels, and it is around them that successive layers of bone are deposited, until at length the vessels become entirely included, and a perfect canal is formed.

In transverse sections of long bones, grooves and partially developed canals may generally be seen along the outer margin of the cutting.

This view of the formation of the Haversian canals also accords well with other characters presented by transverse sections of bone. Thus, in all such, it will be seen that the smallest Haversian canals are situated in the external part, while the larger canals are placed internal to these : it will also be observed, that the smaller canals are surrounded by the fewest number of concentric lamellae, and the larger by the greatest number. (See Plate XXXII. fig. 1.) Now, the fact of an additional number of lamellae encircling the larger canals proves two things: first, that these large Haversian channels are of older formation than the small; and second, that each lamella grows or expands after its deposition, whereby the calibre of such canals becomes increased, which is contrary to the generally entertained notion of the formation of the Haversian canals, viz : by the filling up of the large cancelli, brought about by the continual deposition of new osseous lamellae, the outermost of which, for such a result to ensue, must remain stationary in point of size.

ACCIDENTAL OSSIFICATION.

The abnormal growth and development of bone is a very common pathological occurrence. Thus, we have it occurring on the surface

  • See No. x. Med. Chir. R. p. 528.


BONE. 383

of the bones themselves in the form of exostoses, in the permanent cartilages, in the cellular tissue of muscles, glands, the ovaries, membranes, as the coats of the arteries, and probably occasionally also in that of every other tissue and organ of the body.

It is not, however, every ossific deposit which presents all the characters of bone: thus, those contained in the ovaries, in the mesenteric glands, and in the coats of the arteries, usually want the more conspicuous elements of bone, the bone cells and lamellae, although these have been met with in ossific depositions remote from all connexion with bone.

In the reparation of fractures, we have a development of true bone preceded by the formation of cartilage.


334 TH"E SOLIDS.


BONE.


[Longitudinal and transverse sections of bone, to display the true structure, require so much time and trouble in the preparation, that when it is possible to purchase them, this course will be found to be more advisable. For those who desire to make their own preparations, the following instructions are added :

A section, either longitudinal or transverse, having been made as thin as possible with a fine saw, it must be reduced still farther by a flat file.

When this process cannot be farther carried on, the section is to be placed between two hones, and being kept moistened with water, the honing is to be pursued until the section becomes sufficiently thin to show the structure. This point should be ascertained by occasional observations with a low power of the microscope. When sufficiently reduced, the section may be polished by carefully rubbing it on a strip of chamois-leather with putty-powder.

If it be very thin, it should be mounted dry ; in this condition, a good polish will much increase its value; but if the section be not very thin, it should be made more transparent by being mounted in balsam; in this method, no polish will be necessary.

Mr. Quekett has observed that in some instances when the bone was deposited in balsam, and heat then applied until the balsam has boiled, the structure of the bone has been beautifully displayed.

Sections of bone, before being mounted, should be cleansed from grease and dirt by being soaked for some hours in sulphuric ether.

" The vessels of bone may be recognised while it is yet fresh by the colour of the blood contained in them, but they are rendered much more conspicuous by injecting a limb with size and vermilion, depriving the bones of their earth by means of an acid ; then drying and putting them into oil of turpentine, by which process, the osseous tissue is rendered transparent, while the injected matter in the vessels retains its red colour and opacity."*

As already stated in the text, the lamellae are easily separated by maceration in dilute hydro-chloric acid.]

  • "Quain's Anatomy," by Sharpey and Quain, 5th ed.


TEETH. 335


Article XVI. — The Teeth

The tissue of the teeth is to be regarded rather as a modification of the osseous, than as a distinct type of structure : the truth of this remark is especially apparent on an examination of two of the three substances which enter into the formation of each tooth, viz: the cementum and dentine ; the third constituent, the enamel, is more nearly related in its organization to the epithelium, of which indeed it is a condition.

Each tooth consists of two parts: the body or crown, and the root or fang; the limits of these are indicated by a slight contraction called the neck; the crown is either simple or divided, and the same is the case with root also : those teeth which have a simple crown are called incisors and canines, those with a double crown bicuspids, and those with the crown quadruply divided molars. Again, the substance of each tooth is divisible into three portions, each of which presents characteristic differences; these have received the names of dentine, cementum, and enamel.

The dentine, also called the ivory, forms the chief bulk of the tooth, occupies a central position, and its interior contains the pulp cavity.

The enamel forms a layer of compact substance, which immediately surrounds that portion of the dentine of which the crown of the tooth is made up.

The cementum, also called crusta petrosa, has a distribution the very reverse of the enamel, and extends principally around the fangs of the teeth, and terminates at the neck of the tooth, in fact, just where the enamel commences.

STRUCTURE OF THE TEETH.

Having thus sketched the general position of the three constituents of the teeth, the consideration of the intimate structure of each may next be entered upon.

Dentine. — The dentine is constituted of numerous tubes imbedded in an inter-tubular substance; these tubes commence at the pulp cavity, on the surface of which they open, and from which they proceed in a radiate manner, terminating on the borders of the dentine ; those arising from the upper part of this cavity ascend almost vertically, those from the sides more obliquely, and those from the lower portion pass either horizontally outwards, or else descend somewhat.

These tubes diminish in size from their commencement to their termination: they are branched; at first they divide in a dichotomous manner; their subsequent ramifications are numerous, minute and arborescent, and they inosculate freely with the similar branches proceeding from the adjacent tubes : those tubes which proceed towards the cementum are remarkable for the very great number of branches into which they divide.

The tubes of the dentine in their passage outwards do not run in straight lines, but describe in their transit two or three large curves, and each of these primary curves, when examined with a higher power of the microscope, will be observed to be made up of numerous smaller and secondary curves ; both the large and small curvatures of one tube correspond with those of another.

Such is the usual course and distribution of the tubes of the dentine : several modifications of them, however, still remain to be noticed.

Thus, sometimes a tube in its passage will dilate into a bone cell, and again proceed onwards to its destination as a tube; at others, a number of them, even in the centre of the dentine, will break up and form a cluster of bone cells; again, at others, the tubes frequently become transformed into, or terminate on the margin of the dentine in bone cells. This gradual transformation of the dentinal tubes into bone corpuscles, and their termination in the same, is especially seen in that portion of the dentine contiguous to the cementum.

The usual method of termination of the dentinal tubes, is in fine and inosculating branches on the surface of the dentine. Sometimes, however, the tubes anastomose in a peculiar manner, and form distinct loops; at others, the terminal branches pass out of the dentinal substance, and extend either into the cementum or the enamel; this extension into the former is a very frequent occurrence.

For illustrations of these several modifications, the majority of which have been pointed out by Mr. Tomes, in his excellent lectures,* see the figures.

The surface of the dentine presents many elevations and depressions : to these the enamel is accurately adapted ; it also exhibits the hexagonal impressions of the enamel fibres.

The substance of the dentine is seen also occasionally to be traversed with canals for blood-vessels, analogous to the Haversian canals of bone.

  • See " Lectures" in Medical Gazette.


TEETH. 337

The pulp cavity of the teeth of old persons frequently becomes filled up, and even obliterated, by a secondary formation of dentinal substance, and which may be called the secondary dentine. This dentine results from the ossification of the pulp by the vessels of which it is ttaversed, and from the margins of the canals containing which the dentinal tubes proceed in a radiate manner. (See the figures.)

Mr. Nasmyth regarded this secondary dentinal formation as distinct from the other structures of the tooth, and called it the fourth dentinal constituent.

The dentinal tubes form but one element of the dentine ; the other is the inter-tubular substance.

This is described by Mr. Nasmyth as constituted of elongated cells, in the form of bricks placed end to end, and a tier of which exists between every two tubes : Henle, on the other hand, declares it to be fibrous. It would appear not to present any regular tissue, but to be simply granular.

Occasionally, I have encountered in it globules of various sizes refracting the light strongly, and presenting the appearances of oil or fat vesicles. It has occurred to me that these might be fat cells which had become included in consequence of the ossification of the pulp, and which always contains a greater or less quantity of fat cells. (See figure.)

Some sections of dentine which I have examined have exhibited numerous reticulated markings, the results of fracture of the intertubular tissue, and occasioned probably by the preparation of the section. Fracture of the dentine is capable of reunion.

Cementum. — Of the cementum it will not be necessary to say very much, it possessing the structure of bone, and containing both bone cells and Haversian canals; the latter, however, but seldom. (See the figures.)

The quantity of cementum differs in different teeth ; in many cases it is very inconsiderable, but it usually increases with age.

In those cases in which there is but a slight development of cementum, a layer of considerable thickness, formed of numerous more or less hexagonal cells, and extending over the whole of that portion of the dentine not covered by enamel, may, in most cases, be clearly seen.

This layer, Mr. Tomes speaks of as a granular layer; it is, however, distinctly and regularly cellular. It is not easy to decide whether it should be regarded as a distinct and permanent structure of the tooth, or

22


whether it merely forms the basement substance in which the cementum is developed; my own impressions incline to the former view.*

A layer of granules, having the aspect of imperfectly developed bone cells, is usually situated apparently between the dentine and cementum, but really in the substance of one or other of these; this layer might well be called the granular layer, and to it the description of Mr. Tomes seems more applicable.

Mr. Nasmythf describes the cementum as passing over the entire surface of the enamel of the tooth ; this would appear, so far as the human tooth is concerned, to be an error. A cellular lamina, however, does really invest the enamel in very young teeth, but this is soon worn away: this layer, however, has nothing to do with the cementum, but is considered by Mr. Tomes to be derived from the inner surface of the membrane of the tooth sac. It may be seen in the teeth of the calf and horse.

Cementum is rarely, if ever, developed in the pulp cavity, although it has been stated to be so by many observers. The cementum is not unfrequently traversed by tubes, similar to and derived from those of the dentine.

It will now be very evident that dentine and cementum do not differ essentially from each other, and that both are but modifications of ordinary bone.

Enamel. — Examined with an object-glass of one-fourth of an inch focus, the enamel exhibits a fibrous appearance.

The fibres radiate outwards from the surface of the dentine, somewhat in the same manner as do the dentinal tubes themselves; they are simple, short, somewhat attenuated towards either end, and pass towards the margin of the enamel in a waved manner, sometimes decussating, forming plaits or folds, and this occurs especially when the surface of the dentine is concave. Viewed with a glass of the eighth of an inch focus, they present the appearance of elongated and many-sided crystals, and in transverse sections they are seen to be hexagonal or polygonal ; in some instances, however, and especially

  • The following is Mr. Tomes's description of this layer : " In the inter-tubular

tissue, hemispherical or elliptical cells are found, especially near the surface of the dentine of the fang, where they form a layer joining the cement. This, in a paper read before tbe Royal Society, I described as the granular layer; on the coronal surface of the dentine they are not numerous. With these cells the dentinal tubes communicate, as do others coming from the cemental cells."

f Memoir read before the Medico-Chirurgical Society, by Alexander Nasmyth, Jan. 22d, 1839.


TEETH. 339

in the enamel fibres of young teeth, a minute canal may be traced running along each fibre. (See the figures.)

It is uncertain whether each fibre is constituted of a single cell, or whether several unite to form it : the appearance, in some cases, of faint transverse markings would render it probable that the latter opinion is the correct one.

Near the surface of the dentine, linear interspaces may sometimes be noticed between the enamel fibres; with these spaces the tubuli of the dentine frequently communicate, and when they exist in any number, or extend nearly through its entire thickness, they produce a pearly appearance of the enamel, and render it brittle.

Thin longitudinal sections of the enamel, in connexion with the dentine, generally exhibit numerous linear fractures, which extend through its entire thickness, and which most probably arise from their mode of preparation. Sections of enamel also usually present numerous wavy lines, and which are occasioned by the instrument employed in making the cuttings.

Structure of the Pulp.

The centre of the dentine of all teeth is hollowed out into a cavity; this is occupied with a soft and reddish mass, easily separable from the walls of the cavity, the pulp.

The pulp is made up of numerous blood-vessels, the walls of which are constituted of delicate and nucleated cells, of nerves, or ganglionic cells, and larger granular cells placed principally on the surface of the pulp, external to the other structures which enter into its formation.

These external granular cells are supposed to play an important part in the development of the dentine, and to which more particular reference will be made hereafter.

The pain experienced in tooth-ache arises from inflammation of the nerves of the pulp, and which is frequently left exposed to the contact of the air in consequence of the removal of the dentine, by which in sound teeth it is enclosed, as the result of caries.

DEVELOPMENT OF THE TEETH.

The subject of the development of the teeth may be considered under two heads : under the first, the general development of the teeth will be briefly noticed; and under the second, the special development of their several constituents will be treated of.

Into the various particulars in reference to the general development of the teeth as organs, it would be inconsistent with the design of this work to enter at any length. It will be sufficient to observe, that preparations are made for the formation of the milk teeth at a very early period of intra-uterine life ; that the first trace of the future tooth is manifest in the form of a papilla placed in the primary dental groove, and consisting of granular and nucleated cells ; that around this papilla a membrane is developed, with an open mouth, thus forming a follicle; from the margins of this aperture processes of the mucous membrane, of which the follicle is constituted, are developed, and these uniting with each other close the opening, and convert the follicle into a sac. With the closure of the mouth of the follicle, the first or follicular stage of the development of the teeth is terminated, and the second or saccular stage commences. The number of opercula developed from the margins of the follicles is determinate, being two for the incisives, three for the canines, and four or five for the molars. In the second or saccular stage, the papilla takes the form of the tooth, of which it is the representative, the base dividing in the case of the molars into fangs, and its apex assuming the shape of the crown of the tooth, in the place of which it stands : in this stage also a blastemic matter, consisting of plasma and nucleated cells, is developed in the space intervening between the papilla and the sac, and adherent to the inner surface of the membrane of the latter, by which, indeed, it is generated; lastly, the papillae become capped with tooth substance or dentine.

With the passage of the teeth through the gums the saccular stage terminates, and the third or eruptive stage is entered upon.

The second or permanent teeth pass through stages precisely similar to those of the first or milk teeth, the papillae and follicles being developed in crescent-shaped depressions placed in the posterior walls of the follicles of the milk teeth, and which together constitute the secondary dentinal groove.*

Having now obtained a general idea of the development of the

  • For further particulars relating to the general development of the teeth, consult

the admirable paper of Mr. Goodsir, contained in the Edinburgh Medical and Surgical Journal. From the researches of that gentleman we learn that the papillee of the teeth appear in the upper jaw before the lower; that those of the milk teeth are developed in three distinct divisions — a molar, a canine, and an incisor; that the molar is the first formed, the canine the second, and the incisor the third; also, that the first molar is developed before the second, and the first incisor before the second. In the permanent teeth the papillse, with the exception of the anterior molar, appear at the mesial line first, and proceed backwards.


TEETH. 341

teeth, we shall be prepared to understand the mode of development of the individual tissues of the teeth, a subject which has been studied more particularly by Mr. Nasmyth, Professor Owen, and Mr. Tomes.

Formation of the Dentine. — It would appear to be a universal law of development, that all animal and vegetable tissues should take their origin in cells; of this law the teeth present a striking and beautiful example.

Thus, the dentine is formed out of the cells placed on the formative surface of the papilla or dentine pulp. This view of the formation of the dentine originated with Mr. Nasmyth,* and its accuracy has been confirmed by the investigations of subsequent writers, and especially by those of Professor Owen and Mr. Tomes.

Mr. Owen, in his work, "Odontography," describes with great minuteness the several steps of the conversion of the cells of the pulp into dentine, and also enters upon the consideration of the development of the other tissues of the teeth.

According to Mr. Owen, the cells of the pulp, which are larger and more numerous on the surface, become arranged in lines which are placed vertical to that surface; subsequent to this arrangement, the nuclei are seen to divide, first longitudinally into two portions, each of which becomes a perfect cell, also provided with a nucleus; these again divide, but in a contrary direction, viz : transversely ; thus, four secondary cells are formed within the cavity of the primary cell, and out of its single nucleus. The number is not, however, limited to four, but each nucleus may give origin to many secondary cells. The primary cells are placed end to end, as are also the secondary cells; these last elongate considerably, until at length they coalesce, thus forming the tubes of the dentine ; the primary cells remaining as such, and in some adult human teeth being faintly visible. The primary and secondary cells, however, although placed end to end, do not form straight lines, but describe greater and lesser curves, the greater being formed by the primary cells, and the lesser by the secondary; these are the curvatures to which reference has been made in the description of the tubes of the dentine.

The views of Mr. Tomes,f although not essentially at variance with those of Professor Owen, yet differ from them in some important particulars. Mr. Tomes describes the primary cells themselves as dividing longitudinally into two or more secondary cells, but not transversely ; subsequent to this division, each cell elongates, and at length unites with those above and below it ; thus forming the dentinal tubes. Sometimes two cells unite with but a single cell placed beneath it, and it is in this way that the branches of the dentinal tubes are produced, Thus, according to Mr. Tomes, the wall of the primary cell, as well as its nucleus, enters into the formation of the dentinal tubuli ; while, according to Professor Owen, the nuclei alone give rise to these tubes, the walls of the parent cells not undergoing elongation, but remaining to constitute a considerable portion of the inter-tubular tissue.

  • Memoir on the Development and Organization of the Dental Tissues," by Alexander Nasmyth, August, 1 836.

t Medical Gazette, Lecture V.


In the human tooth I have been unable to detect the existence of the primary cells of the dentine.

Covering the dentine pulp, a thin transparent membrane exists; this, on its outer surface, is marked with numerous hexagonal depressions, into which the enamel fibres are received.

Formation of the Enamel. — Reference has been made to a blastemic matter, consisting of nucleated cells imbedded in a granular matrix, and situated between the dentine pulp and the inner surface of the sac of the tooth; this is the enamel pulp.

The cells of which this is formed are larger than those of the dentinal pulp, more transparent, and with nuclei which are less distinct; they adhere to the inner surface of this sac, which is formed of a process of the mucous membrane of the mouth itself, and from which, indeed, they are evolved.

This membrane, like all mucous membranes, consists of two layers, an outer basement of fibrous and vascular layer, and an inner colourless and blastemic layer; and it is from this last that the enamel cells proceed. It is marked with depressions similar to those existing on the surface of the membrane of the dentinal pulp, and into which the terminations of the fibres of the enamel are received.

It is out of the cells just described that the enamel fibres are formed, and this in a manner almost similar to that in which the tubes of the dentine are themselves developed; thus the cells are first arranged in vertical lines ; these commence in the depressions on the inner surface of the tooth sac, and proceed from without inwards. The cells next elongate until they touch each other by either short or oblique surfaces; some of them coalesce by their extremities, and thus form fibres in which earthy matter is deposited, and which at length terminate in the hexagonal depressions situated on the outer surface of the membrane of the pulp of the dentine.


TEETH


313


The nuclei elongate with the cells, and either disappear altogether, or else remain as minute cavities running down the centre.

At first the union between the fibres is but slight, so that in newlyformed enamel they may be easily separated from each other when placed in water, to which they will impart a whitish appearance, in consequence of their separation and diffusion through the fluid.

According to Mr. Tomes, also, numerous spaces exist between the fibres in newly-formed enamel; and it is owing to the presence of these that young enamel owes its opacity and brittleness.

We thus perceive that the enamel is to be regarded rather as a modification of the epithelium than of bone.

The development of both dentine and enamel may be well studied upon the teeth of young pigs, or kittens, at the birth.

Formation of Cementum. — The cementum pulp is formed between the external surface of the dentine and the internal of the sac of the tooth, it being intimately united to both.

It consists, like the pulps of the other tissues of the teeth, of nucleated cells imbedded in a granular matrix: these cells are described by Mr. Tomes* as resembling those of temporary cartilage, being oval in shape, and having their long axes placed transversely, and at right angles, to the length of the tooth.

The cells nearest the surface of the dentine are the first to become ossified; and when their ossification and development is completed, they form the stellate or bone cells of the cementum. Some consider that the nuclei of these cells alone give origin to the bone cells, and appearances may be observed, even in adult cementum, which are favourable to this opinion.

The cementum is often seen to be traversed by fibres derived from the outer layer of the membrane of the tooth-sac, as well as by tubes prolonged into it from the dentine.

Notice has already been taken of the small hexagonal cells contained in the cementum, and situated principally upon the outer surface of the dentine, and a doubt was expressed whether these were to be regarded as forming a part of the structure of the cementum, or whether they constituted a distinct organization.

The cementum is particularly liable to an increased and abnormal development constituting exostosis.

It would thus appear, on the one hand, that the cementum and dentine are but modifications of each other, and also of one and the same tissue, the osseous; while, on the other, it is evident that the enamel is a modification of the epithelium.


  • See Lecture V.


Mr. Nasmyth describes the cementum as passing over the crown of the tooth and surface of the enamel, in a thin layer composed of hexagonal cells and fibres; this layer exists only on the surface of the enamel of the young teeth of the human subject, and it is not composed of dentine, but consists of either a few of the unelongated cells of the enamel pulp, or, as Mr. Tomes considers, of the inner surface of the sac of the tooth.

Nature of Caries of the Teeth.

Various opinions have been entertained in reference to the nature of the peculiar decay denominated caries, to which the teeth are so liable. Some have supposed that it is a vital process resulting from inflammation. The fact that dead teeth, that is, teeth which have been removed from the jaw and are again employed as artificial teeth, undergo a similar decay to that which affects the living teeth, proves that it is not essentially a vital action, although it cannot be questioned but that the condition of vitality and the state of development of the teeth must exert a powerful influence over the progress of the decay. Other observers regard the decay of the teeth as a purely chemical phenomenon, the earthy matter of the teeth being removed by the action of free acid in the saliva: this view of its nature certainly explains many of the circumstances connected with dental caries, and is supported by the fact already cited, viz: that dead teeth are susceptible of the change.

Two facts, however, require to be determined before the chemical theory of the decay of the teeth can be considered to be proved ; first, that the saliva is in every case of dental caries really acid; and second, that the portion of the tooth which is subject to the carious action is really dead : upon both of these points considerable doubts may be entertained.

For myself, I have long entertained the idea that the real and proximate cause of the decay of the teeth was to be found in the presence of some parasitical production, and that the condition of vitality of the teeth and of the states of the saliva were to be considered merely as predisposing causes to the affection.

This idea acquires some confirmation from an examination of the carious matter of a tooth; in it vast quantities of minute threads or filaments, possibly those of a fungus, are invariably to be discerned,


TEETH. 345

as well as numberless dark granules and irregular masses, bearing in some cases the aspect of true cells.

The question may be asked, are these threads, granules, and celllike masses any thing more than the decomposing elements of the dentine, in which tissue it is that the chief ravages of the decay occur ? The answer is, possibly not ; but the surprising numbers of these filaments and the testimony of Mr. Tomes are opposed to the idea that they are the remains of the tubes of the dentine. Mr. Tomes thus writes in his tenth Lecture in reference to the tubes of the dentine : " A transverse section of carious dentine, rendered soft like cartilage from the loss of its lime, presents a cribriform appearance. The tubuli seem enlarged and rather irregular, quite unlike the figure they present in healthy dentine : this would indicate that the solvent enters and acts upon the parietes of the tubes previous to affecting the inter-tubular tissue, and that the parietes of the tubes are therefore the first to disappear. I feel quite certain that in the cases I have examined, and they are numerous, the parietes of the tubuli, so distinguishable in healthy dentine, have almost, if not wholly, disappeared with the removal of the lime."

Nature of Tartar on the Teeth.

Tartar of the teeth consists of phosphate of lime mixed up with the mucus of the mouth and epithelial scales: it contains also occasionally animalcules and vegetable growths, which find in the animal matter of the tartar a convenient nidus for their development. The accumulation of tartar around the necks of the teeth results from an opposite condition of the saliva to that to which chemists ascribe dental caries, viz: an alkaline state of it.


TEETH.

[The substance of the teeth being harder than that of bone, thin sections, which should be made in different directions, must be first cut by means of a lapidary's wheel charged with emery or diamond-dust. These sections are then farther reduced in the same manner as those of bone — first, by the files, next by the hones, and lastly polished. Like bone, they may be either mounted in balsam or dry ; the latter method is. preferable when the section is sufficiently thin to show well the structure.]


Article XVII. — Cellular or Fibrous Tissue

The truth of the scientific dictum, that every living thing proceeds from a germ or ovum, is now generally admitted, and so also it may be said that each portion of the fabric of such living entity takes its origin in a cell, the early and embryonic condition of every organ and structure being reducible to that of a cell.

It was not, however, this consideration that induced the older anatomists to apply the term cellular to the tissue about to be described, they having but little knowledge of the structure of the elementary cell, or of its universal presence.

They were led to denominate the tissue, into the description of which we are about to enter, cellular, in consequence of observing the areolae or spaces left between the fibres of which it is composed, and which they erroneously considered to be cells. The cellular tissue, then, though like all other tissues, taking its origin in cells, inasmuch as in its fully developed state it consists of fibres, would be more accurately denominated the fibrous tissue, as indeed by many modern anatomists it really is : the term cellular tissue is, however, one of so ancient a date, and one, moreover, in such general use, and so well understood, that it seems to be scarcely advisable to abandon the use of it altogether.

The cellular or fibrous tissue, however, as ordinarily encountered, is constituted not of a single description of fibre, but consists of two kinds intermingled in different proportions, and each of which is possessed of distinct characters and properties.

The most remarkable difference between the two descriptions of fibrous tissue is, that the one is white and inelastic, and the other yellow and elastic : each of these will be described under different heads, and the former before the latter.

INELASTIC OR WHITE CELLULAR OR FIBROUS TISSUE.

Tendons, Ligaments, Membranes, fyc.

The inelastic fibrous tissue is very generally distributed throughout the body: it constitutes the principal portion of tendons, ligaments, and fasciae : of the fibrous membranes, the dura mater, pericardium,


CELLULAR OR FIBROUS TISSUE. 347

periosteum, perichondrium, tunica albuginea of the testicle, and sclerotic coat of the eye; also, of the serous, synovial and mucous membranes, as well as of the skin, and it forms likewise the principal constituent of the loose cellular tissue which is so abundantly developed throughout every tissue and organ of the body, but which is invariably present in large quantities wherever motion is necessary, as in the axilla, between the fasciculi of muscles, and in the course of the vessels.

When endowed with a distinct form, as in the case of the tendons, it may be called morphous inelastic cellular tissue, and when it has no circumscribed shape, the term amorphous may be applied to it: when constituting membrane, it exists in the state of condensed fibrous tissue ; and when it merely binds organs together, or allows of the motion of parts, it maybe called loose or reticular cellular tissue.

There is, however, a form of the inelastic fibrous tissue which requires not merely a separate name, but a distinct notice. This form is met with in the great omentum, and consists in the fact of spaces of irregular size and form being left between the fibres, and hence it may be termed areolar cellular tissue. The best examples of it are met with in the omenta of children and lean persons, which contain but little fat. (See Plate XL. fig. 4.)

The inelastic cellular tissue is made up of innumerable unbranched threads or fibres of equal calibre, of great tenuity, which appear white to the unassisted sight, but of a yellow colour when viewed under the microscope, and which have a great disposition to assume a waved or zigzag arrangement, the folds formed being comparable to those in which a loose skein of silk is often observed to fall. (See Plate XXXIX. fig. 6.)

When dried, the inelastic cellular tissue assumes the transparent appearance and consistence of horn; in water, the fibres swell up somewhat, become opaque and white, but still preserve their form : in acetic acid, they swell up greatly, become indefinable, soft and gelatinous: the addition of a mineral acid will, however, bring the fibres again into view. A

The remarkable effect of acetic acid on the inelastic fibrous tissue, has suggested the idea to Mr. Bowman that "it is rather a mass with longitudinal parallel streaks (many of which are creasings), and which has a tendency to slit up almost ad infinitum in the longitudinal direction."

There are several considerations which may be urged in disproof


348 THE SOLIDS.

of this view; the first is, the mode of development belonging to this tissue ; the second, the fact that the fibres are all of nearly an equal diameter; and the third is, that the tissue still retains its fibrous constitution even after the application of acetic acid.

The white fibrous tissue is employed wherever a strong and inelastic material occupying but little space is required.

A degree of elasticity not unfrequently appears to belong to this tissue; but this is rather apparent than real, and depends upon the extent of its admixture with the next form of fibrous or cellular tissue to be described, viz: the elastic. (Plate XXXIX. jig. 1)

ELASTIC CELLULAR OR FIBROUS TISSUE.

The elastic cellular or yellow fibrous tissue is distinguished from the inelastic form by its branched filaments, the diameter of which is unequal, its elasticity, its deeper colour, and the absence of any appreciable effect on the addition of acetic acid. (See Plate XL. jig. 1.)

Like the inelastic fibrous tissue, it rarely occurs in an unmixed form, being mostly intermingled with it in variable proportions : thus, it is encountered in tendons, ligaments, and, indeed, in all forms and conditions of the inelastic cellular tissue; it constitutes the principal portion of the ligamenta sub-flava and nuchas, of the transverse fascia of the abdomen, of the crico-thyroid and thyro-hyoid membranes, of the chordae vocales, of the internal lateral ligament of the lower jaw, of the stylo-hyoid ligaments, of the middle coat of the arteries, and of the membrane uniting the rings of the trachea and its ramifications. It is also met with in considerable quantities beneath the mucous membrane of the oesophagus, at the base of the epiglottis, in maintaining which in the erect position it is probably mainly instrumental, in the lungs and in the integuments of the penis.

The elastic cellular tissue presents some differences of appearance and structure, in certain of the situations in which it is encountered : thus, in the tendons and in the smaller blood-vessels (Plate XL. jigs. 1, 2, 3. 5) the fibres are very slender, appear to be but little branched, and contain at intervals nuclei in the same manner as do the fibres of unstriped muscles; in the reticular cellular tissue again, they are slender, unbranched, and without nuclei (see Plate XXXIX. jig. 7) ; in the ligamenta flava and nucha?, in the crico-thyroid and thyro-hyoid membranes, the fibres are thick, much branched, curled, and interwoven, but they do not present nuclei (see Plate XL. jig. 1) ; in the larger arteries, the fibres are slender, and are united together so as to


CELLULAR OR FIBROUS TISSUE. 3 19

form areolae (see Plate XL. fig. 2), while in the smaller blood-vessels they are distinctly nucleated, as already observed.

There is little doubt but that the several forms of elastic tissue just described do really represent different stages and states of the same structure ; and it will be observed, that some of them, and especially that of the small blood-vessels, approach very closely in structure and appearance to that of unstriped muscular fibre : the fibres of the former differ, however, in being sparingly branched, and in their more slender diameter.

It is not easy, without the addition of reagents, to distinguish the two forms of fibrous or cellular tissue from each other when mixed together: nevertheless, when the two are well separated, the elastic fibres may be frequently singled out from the inelastic, in consequence of their presenting a darker and stronger outline, as well as of their following a more curled and tortuous course. (See Plate XXXIX. fig. 7.) Acetic acid applied to a portion of mixed cellular tissue, at once allows the elastic fibres to be clearly seen, rendering the inelastic fibres transparent, and almost invisible.

There are several parts of the human organization described by modern minute anatomists and physiologists as being in part composed of unstriped muscular fibre; these are the skin, dartos, nipple, clitoris, penis, the ducts of the larger glands, as the ductus communis choledochus, the ureters, and vasa deferentia. Now, I find that all these parts, which I have examined with care, owe their contractility, and their power of erection, to the presence of the nucleated form of the elastic tissue which has been described as existing in tendons and the smaller blood-vessels, and not to any form of muscular fibre; and further, that in the majority of them, and especially in the dartos, penis, clitoris, and nipple, this elastic tissue is confined almost entirely to the blood-vessels, the walls of which it constitutes : this fact may be readily ascertained in the instance of the dartos by taking a small fragment of that membrane when in a fresh condition, and having spread it out on the surface of a piece of glass without the addition of any fluid, then submitting it to the microscope, when the number, size, and course of the blood-vessels may be traced, and the disposition of the intervening fibrous inelastic tissue recognised: in the recent state, however, the vessels are filled with blood, the presence of which prevents the satisfactory detection of the elastic constituent of the blood-vessels : if now, however, acetic acid be applied to the fragment of membrane thus spread out, the inelastic fibrous tissue will become


350 THE SOLIDS.

indistinct, the red blood corpuscles contained in the vessels will be dissolved, and the tissue of the blood-vessels clearly brought out. (Plate XLIII. fig. 3.)

The extent of contraction of which the dartos is susceptible is verygreat, and the act of contraction must of course exert a very powerful influence over the circulation of the blood in its vessels. In the contracted state of this membrane, the slender fibres of the elastic tissue, as well as their nuclei, are frequently curled up in a spiral manner, an arrangement by which any amount of shortening may be secured.

The contraction of the tissue of the dartos, and indeed of all elastic tissue, is evidently not a physical, but a vital act: this is shown by the relaxation and contraction which it experiences in sympathy with the condition of the vital powers, as well as with any causes, as heat and cold, which affect these powers.

The corpora cavernosa penis and corpos spongiosum urethrae are almost entirely composed of blood-vessels, and the peculiarity of these parts consists in the large size of the vessels, and in their repeated inosculation. (Plate XLIII. j%. 4.)

In the lungs, the blood-vessels are so numerous, that they, in this case, also constitute the principal portion of the fabric of these organs: — this may be beautifully seen in the lungs of the lower reptiles, as the triton and frog.

Henle has described a peculiar arrangement of the fibres of elastic tissue. "I have already said," he remarks, "that the fibres of the cellular tissue are for the most part united into a number more or less considerable, and thus form flattened bands of different thickness. These bands unite in their turn to produce others larger, or even membranes, and thus, sometimes they apply themselves parallelly to each other ; at others, they cross each other in the most varied directions. When the cellular tissue fills the interstices of organs under the form of a soft mass, easy to displace, and extensible, the bundles may be perceived without the least preparation, seeing that they cross and interlace in all directions, and that even to the naked eye, they represent a net-work of delicate fibres. The size of the bundles, which I call primitive bundles, or after their origin, the fibres of the cells of cellular tissue vary from the 0'003 to the 006 of a line. The majority of the primitive bundles are deprived of special envelope: the fibres may easily be detached, the one from the other, and separate, when one bends a bundle strongly. But in many


CELLULAR OR FIBROUS TISSUE. 351

situations they are interlaced, and held together by filaments, which differ from the fibres of cellular tissue by their chemical and microscopical peculiarities, while in certain respects they approach the fibres of elastic tissue; of which we shall give a description further on. They are almost still finer than the fibres of cellular tissue, quite flat and homogeneous, but with outlines much more obscure, and they are distinguished, above all, by the considerable folds, which they describe when they are in a state of separation. In order to recognise them, it is necessary to place the cellular tissue in contact with acetic acid : in this acid the bundles of cellular tissue become transparent, swell, and cease to appear fibrous, while the filaments which envelope them undergo no change. In this manner it happens that a bundle, which appears to be composed of the ordinary interlaced fibres of cellular tissue, comports itself after having been treated with acetic acid, as a transparent cylinder divided by contractions often very regular, and which one soon observes to be caused by a filament which runs spirally around the bundle; or also by separated rings placed at a greater or less distance from each other I have rarely succeeded in reducing the turns to a single filament, and I am obliged in consequence to leave undecided the question, whether it does not sometimes happen that many filaments are rolled spirally around a bundle. The formations which I have described show themselves in no part in a more beautiful manner than in the delicate and firm cellular tissue, which is situated at the base of the brain beneath the arachnoid, between the vascular trunks and the nerves, and which becomes distended into isolated filaments, on extension, as, for example, in any part of the circle of Willis. There I have never sought the spiral filaments in vain; nevertheless, analogous bundles, encircled with spirals, may be seen also upon other parts of the economy, in serous membranes, in the sub-cutaneous cellular tissue, in the skin, and even in the tendons."*

It appears to me that Henle has misunderstood the structure, and consequently the nature of the formations noticed by him: there can A be little doubt but that these, in place of being bundles of filaments composed of inelastic fibrous tissue encfrcled with a spiral coil of elastic tissue, are in reality hollow cylinders, vessels in fact in progress of formation, consisting of, in the stage described by the German physiologist, an inner transparent and apparently structureless tunic, enclosed in a coil of elastic fibrous tissue.

  • Anal. Gen. vol. i. pp. 377, 378.


352 THE SOLIDS.

The correctness of this view is established by the very convincing fact, that the tubular formation in the condition just described may be traced up to the state of perfect blood-vessels, some of which may also now and then be seen dividing into branches, and containing, moreover, blood corpuscles. Several of the stages of the development of these vessels are seen in Plate XL.fig. 3.

DEVELOPMENT OF CELLULAR TISSUE.

Exact observations are still required on the subject of the development of both the elastic and the inelastic forms of the cellular or fibrous tissue, and especially of that of the latter form. Schwann and all other observers after him have described the cellular tissue as taking its origin in cells of an elongated form, from the extremities of which fibres, mostly branched, proceed, the cells themselves ultimately becoming absorbed : microscopists, however, have not as yet attempted to point out the differences which doubtless exist in the development of the two forms of cellular tissue, but have for the most part contented themselves with the above general description.

It appears to me that the observations already made on the development of the cellular tissue apply only to the yellow or elastic kind ; and to this conclusion I am led by the fact that observers describe the elongated nuclei as giving origin to branched filaments; and we know that the fibres of the inelastic fibrous tissue are simple, and not branched.

According to my observations, both forms of cellular tissue originate in cells.

The cells of the white fibrous tissue exist first as rounded nuclei, around which the cell wall gradually makes its appearance, and these cells when fully formed are large, granular, elongated, fusiform, and from each extremity at length proceeds a single unbranched thread, which gradually becomes extended into a filament or fibre, which is produced by the growth and extension of the cell wall itself, and the extremity of which unites for the production of an elongated thread with that proceeding from the other cells placed above and below it : finally, the process terminates by the absorption of the nuclei. (See Plate XLIII.jffe. 2.)

The cells of the yellow fibrous tissue also exist, at 'first as nuclei, then as fusiform cells, but. differ from those of the white fibrous tissue in the subsequent steps of their development, in that the cells are disposed in lines, each fibre being formed, as is the case with the unstriped


DEVELOPMENT OF CELLULAR TISSUE. 353

muscular fibre, by the union of the filaments, proceeding from each series of linearly disposed cells, and in that the filaments proceeding from the cells are very frequently branched. (See Plate XXXIX. figs 1, 2. Plate XL. figs. 3. 5.)

The above-described mode of development may be followed out in longitudinal and cross sections of tendon treated with acetic acid; also, in the smaller vessels of the pia mater, and in those placed in the mixed cellular tissue which separates the different striped muscular fasciculi: we thus perceive, that in the case of the yellow fibrous tissue, many nuclei are required to form a single filament ; and further, that there is a strong analogy in the mode of its development with that of muscular fibre, as also in the physical properties of the two tissues.

In the fibrillation of the fibrin of the blood we have an example of the formation of filaments independently of any development from cells, and at one time I conceived that the fibres of the white fibrous tissue might possibly originate in a similar manner.

23


354 THE SOLIDS.

Article XVIII. — Muscle

Few of the animal tissues have been more extensively examined than the muscular: the multiplied observations made on its structure have, however, led neither to that uniformity of opinion respecting it, nor, indeed, to that accurate knowledge of its minute anatomy, which might have been anticipated; of the truth of this position, evidence will be shortly adduced.

Muscles admit of division into the voluntary, or those which are under the control of the will, and the involuntary, or those of which the action takes place independently of the will; the former consist of the muscles of animal life — those, for example, of locomotion — and the latter embrace those of organic life, as the muscles of the alimentary canal (the sphincters of the oesophagus and anus excepted, which are to a certain extent voluntary), the heart, the uterus, the bladder, &c.

It will be observed, that the involuntary muscles, or those of organic life, usually encircle the hollow viscera; there are some other situations, however, in which involuntary muscular fibres are met with, as in the trachea and its bronchial ramifications, the iris, the sarcolemma, and, according to some observers, as Bowman, they are also encountered in the dartos and covering the excretory ducts of the larger glands, as the ductus communis choledochus, the ureters, and vasa deferentia; and it is with them a matter of question how far the contractility of the skin, and the erection of the penis, clitoris and nipple, may be dependent upon the presence of involuntary muscular fibrillae. In the preceding article I have, however, shown that the contractility of these parts depends upon the presence of a nucleated form of elastic tissue, allied to unstriped muscular fibre in many of its properties, but yet distinct therefrom.

Corresponding with the division of muscles into voluntary and involuntary, there exist differences of structure: thus, the muscles under the control of the will are all striped, while those which are not under its influence are unstriped. To this rule, however, one remarkable exception may be mentioned, viz: the muscles of the heart, the action of which is to a great extent involuntary, and which are yet striped : this exception is rather apparent than real, as will be seen hereafter.


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STRUCTURE OF MUSCLE.

A striped muscle is made up of a number of unbranched fibres, each of which is included in a distinct sheath, the sarcolemma, and consists of a number of threads or fibrillae : the fibres again are collected into sets or bundles called lacerti; these are held together, and yet separated by a mixed form of cellular tissue, which also contains fat vesicles, blood-vessels and nerves.

An unstriped muscle consists of fibrillae, intermingled with fibrous tissue: these do not form fibres, and consequently there is no sarcolemma.

Between striped and unstriped muscle there is no essential or specific structural difference: the one is not to be regarded as typically distinct from the other, but both should rather be considered as different conditions in the development of one and the same tissue. Of this position, evidence will be hereafter adduced.

According to the above view, muscular fibre presents two grand stages of development; the first of which is represented by the unstriped fibrilla, and the second by the striped muscular fibre.

We shall first describe the structure of the unstriped muscular fibrilla, because it represents an earlier condition of development than the striped.

Structure of Unstriped Muscular Fibrillce. — Unstriped muscles consist of fibrillae which are unbranched, rather broad, somewhat flat, and which contain, imbedded in their substance, elongated and granular nuclei. (See Plate X.hl. fig. 2.)

The fibrillae usually run parallel to each other, and form thin layers and fasciculi, which are separated from each other by cellular tissue, and frequently interlace.

The nuclei are sometimes imbedded in the substance of the fibrillae, without at the same time increasing their diameter: at others, they render the fibrillae ventricose from their great size ; and again, in other cases, they protrude from their sides. (See Plate Uhl.fig. 2.) They are best seen after the addition of acetic acid.

Unstriped muscles are doubtless freely supplied with blood-vessels and with nerves.

The unstriped muscle is called into action with greater difficulty than the striped; its action is also slower, and of a peculiar kind, giving rise to the vermicular and peristaltic motion, seen especially in the intestines.


356 THE SOLIDS.

This slower and less energetic action results from its lower degree of organization.

The muscular structure of the heart, the action of which is to a considerable extent involuntary, requires a special description. The muscular tissue of this organ has been usually supposed to constitute an exception in its structure to that of other involuntary muscles, and that while it performed the office of an involuntary muscle, it yet possessed the structure of a voluntary muscle, its fibres being striped.

Mr. Bowman, one of the very best authorities on the structure of the muscular fibre, gives the following description of the tissue of the heart : " The cross stripes on the fibres of the heart are not usually so regular or distinct as in those of the voluntary muscles. They are often interrupted, or even not visible at all. In some of the lower animals their sarcous elements never form transverse stripes. These fibres are usually smaller than the average diameter of those of the voluntary muscles of the same subject by two-thirds, as stated by Mr. Skey."*

This description is very imperfect, and in some respects, according to my observations, incorrect. Thus, the muscular substance of the heart does not form fibres at all, but consists simply of fibrillae, which agree in every respect with those of other involuntary muscles, save in their transverse striation: thus they have the same considerable diameter: they are, in like manner, abundantly nucleated (see Plate XLI. fig. 3), and they have the same arrangement, interlacing with each other, and not forming fibres included in a sarcolemma, as is the case with the voluntary muscular tissue. The transverse striae, too, have not the deep and permanent character belonging to the fibrillas of ordinary striped muscle, as is evinced by the fact that acetic acid effaces all vestige of striation.

It thus appears that the muscles of the heart agree in structure much more closely with that of other involuntary muscles, which is contrary to what is generally supposed, than they do with that of the voluntary muscles.

Thus, then, the structure and the function of the muscles of the heart are in accordance, and not in antagonism, as is usually conceived, the single point of difference between its fibrillae and those of other involuntary muscles consisting in the feeble transverse striation, the presence of which evinces a somewhat higher degree of development, as well as a greater power of contractility.

  • Physiological Anatomy, p. 161.


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St 'ructure of Striped Muscular Fibre. — The striped muscle consists of fibres: each of these is included in a distinct envelope, termed Sarcolemma, and is made up of a number of lesser fibres or fibrillae. (See Plate XLII. fig. 1.)

The fibres vary very considerably in size, not merely in different animals, but also according to the age of an animal, and even in a single bundle of the same animal, some of them being three or four times larger than others, and the smaller being usually adherent to the larger fibres; a fact which has reference to the development of muscular tissue, and which will be explained when we arrive at the consideration of that portion of our subject. (See Plate XLII. fig A) The difference in the size of the fibres according to age is very remarkable, those of the foetus being several times smaller than the fibres of the adult. (See Plate XLIL fig. 1, and Plate XLIII. fig. 1.)

They differ also to a very considerable extent in form as well as magnitude: thus, in a cross-section and in a recent state, they are seen to be more or less angular and compressed, but still preserving, in most cases, much of the character of cylinders. In the dry condition, this angularity is greatly increased, and to this state of the fibres the representations hitherto given chiefly refer. (See Plate XLII. fig. 5.)

The fibres, both great and small, are, as already observed, arranged in bundles or lacerti, of variable size; those of the same bundle run parallel to each other, and the different bundles are separated, and yet held together by mixed fibrous tissue.

Examined with a moderate power of the microscope, each fibre is seen to exhibit numerous transverse striae, which are placed at tolerably regular distances from each other: some fibres, also, and especially such as have been preserved in spirit, present numerous fainter longitudinal striae.

When viewed with a somewhat higher object-glass, and when each fibre has been torn into pieces by needles, its entire bulk will be seen to be made up of a number of slender threads of equal diameter, which present a distinct transverse striation.

It was formerly very generally supposed that the transverse lines on the striped muscular fibre were produced by a filament which wound spirally around it : this notion is, doubtless, erroneous, as indeed it is now generally allowed to be.

It has been observed, that the fibrillae are themselves marked with transverse striae : now, it is not difficult to convince one's self that the


358 THE SOLIDS.

striation of the fibre is produced by the striae of the fibrillar, the striae of one fibrilla corresponding with that of another, and thus giving rise to a line which extends entirely across the diameter of the fibre.

The correctness of this explanation might have been easily inferred from a knowledge of the composition of the striated muscular fibre of banded fibrillae, and from the aspect of the transverse line itself, which, when examined with a high power of the microscope, does not present the appearance of an uninterrupted and continuous line, such as would be produced by the winding of a filament around it, but rather of a line formed by the apposition of a series of dots or shorter lines ; in which manner, indeed, it is that the striation of the fibre is really produced, as we have seen.

The fibrillae contained in each fibre are unbranched, of great tenuity, of nearly equal diameter (see Plate XLII. fig. 1), and their number varies greatly, amounting in the larger fibres to as many as fifty or sixty, while in the smaller they may not exceed from one to five and upwards, according to the breadth of the filament.

The striae present a very uniform and strongly marked character: the spaces between them are not, however, equal: thus, they are sometimes rather longer than the diameter of the fibrilla: at other times, they are shorter, and when the striae are very close, the fibrilla becomes ventricose or moniliform.

Much difference of opinion prevails as to the nature of the striation exhibited by the fibrillae. Drs. Sharpey* and Carpenterf incline to the opinion that each fibrilla consists of a series of particles or cells cohering in linear series, and that the lines indicate the point of junction of these ; Mr. Erasmus WilsonJ attributes a still more complicated structure to the striated fibrilla. He believes that two kinds of cells exist in each fibrilla; a pair of light cells, separated by a delicate line, being interposed between each pair of dark ones.

Lastly, Bowman considers that the lines indicate the divisions between particles, which he denominates "sarcous elements."

My own view of the nature of these lines differs from that of all the gentlemen named. I consider that the lines in question are produced by the simple corrugation or wrinkling of the threads at regular distances : a view, the accuracy of which is all but proved by a consideration of the development of muscular fibre, and by the

  • Quain's Anatomy, 5th edition, vol. ii. p. 168.

f Human Physiology, p. 176.

\ Manual of Anatomy, 3d edition, p. 16.


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action of acetic acid on the fibrillar of the heart, the transverse markings of which it entirely obliterates.

The fibrillae are, as already stated, included in a sheath, the sarcolemma of Bowman, both together constituting the fibre. The sheath cannot at all times be seen: it may, however, frequently be so, and especially when the fibrillae have been torn across, the sheath at the same time not having been divided, its greater elasticity enabling it to resist the force which was sufficient to rupture the muscular fibrillae. It is in such cases that the best view of this membrane is obtained. (See Plate XLU. fig. 1.)

Treated with acetic acid, each fibre discloses most distinctly a considerable number of elongated and granular nuclei, the outlines of which are in some cases visible, even without the application of the acid. (See Plate XLII. fig. 2.)

Of these nuclei, Mr. Bowman remarks: "In the fully-formed fibre, if it be large, they lie at various depths within it; but if small, they are at or near the surface. They are oval and flat, and of so little substance, that though many times larger than the sarcous elements, and lying among them, they do not interfere with their mutual apposition and union." "It is doubtful whether the identical corpuscles, originally present, remain through life, or whether successive crops advance and decay during the progress of growth and nutrition: but it is certain that as development proceeds, fresh corpuscles are deposited, since their absolute number is far greater in the adult than in the foetus, while their number relatively to the bulk of the fibre at these two epochs remains nearly the same."*

The above description is in part only correct. Thus I find, first, that the nuclei are invariably situated on the external surface of the fibre, the majority within the sheath, and either adherent to this, or to the exterior fibrillae, some also being placed on the outer surface of the sarcolemma; facts which throw much light upon the development of the muscular fibre; secondly, that the nuclei are not usually free nuclei, but are contained in most cases in filaments in every way similar to those of unstriped muscle, and with which they are identical.

Were the nuclei really scattered throughout the substance of a muscular fibre, they would infallibly destroy the parallelism of the striae, and greatly interfere with its contractile power.

The interpretation to be given of the location of the nuclei and fibres of unstriped muscle in the situations indicated, will be explained

  • Physiological Anatomy, vol. i. pp. 158, 159.


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when the subject of the development of muscular fibre is considered ; at the same time, also, the point raised by Mr. Bowman, as to the persistence of the nuclei, will be. discussed.

The fibres of the upper part of the oesophagus are striped, while those of the lower half are unstriped. It has been considered a matter of uncertainty whether the two pass by insensible gradations of structure into each other, or whether they terminate abruptly. I believe, after careful examination, that the latter supposition is the correct one.

With a few remarks upon the peculiar views entertained by Mr. Bowman, in reference to the structure of the striated muscular fibre, the discussion of the structure of muscle may be brought to a conclusion.

"It was customary," writes Mr. Bowman,* "both before and since his time (the time of Fontana), as at the present day, to regard the fibre as a bundle of smaller ones, whence the term primitive fasciculus, first given to it by him, and adopted by Muller; but this view of the subject is imperfect.-' The fibre always presents, upon and within it, longitudinal dark lines, along which it will generally split up into fibrillae ; but it is by a fracture alone that such fibrillae are obtained. They do not exist as such in the fibre. And further, it occasionally happens that no disposition whatever is shown to the longitudinal cleavage; but that, on the contrary, violence causes a separation along the transverse dark lines, which always intersect the fibre in a plane perpendicular to its axis. By such cleavage, discs, and not fibrillae, are obtained, and this cleavage is just as natural, though less frequent, than the former. Hence, it is as proper to say that the fibre is a pile of discs, as that it is a bundle of fibrillae : but, in fact, it is neither the one nor the other, but a mass in whose structure there is an intimation of the existence of both, and a tendency to cleave in the two directions. If there was a general disintegration along all the lines in both directions, there would result a series of particles, which may be termed primitive particles, or sarcous elements, the union of which constitutes the mass of the fibre. These elementary particles are arranged and united together in two directions. All the resulting discs, as well as fibrillae, are equal to one another in size, and contain an equal number of particles. The same particles compose both. To detach an entire fibrilla, is to abstract a particle of every disc, and vice versa. The width of the

  • Physiological Anatomy, vol. i. pp. 151, 152.


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fibre is therefore uniform, and is equal to the diameter of any one of its fibrillae, and is liable to the greatest variety."

This view of the structure of the. striated muscular fibre is ingeniously conceived and well expressed; nevertheless, it can be shown, I think, notwithstanding its ingenuity, to be incorrect.

There are two considerations which appear to me to be sufficient to disprove the view just propounded. The first is, that the rudimentary muscular fibre consists of one or more threads or fibrillae, containing imbedded in them a number of elongated nuclei, which, however, have no correspondence with the transverse markings ; and the second is, that, while any muscular fibre may at any time be readily separated into its component fibrillae, the simultaneous transverse cleavage spoken of and figured by Mr. Bowman is an occurrence of extreme rarity, and one, moreover, of which I have never been able to perceive the slightest trace in any muscular fibre which has fallen under my notice.

It would thus appear that the older view is the correct one, and that the striped muscular fibre is made up, as already described, of a variable number of fibrillae enclosed in a tubular sheath.*

Blood Vessels of Muscles. — Muscles are copiously supplied with blood-vessels; the larger vessels are contained in the cellular tissue separating the fascicles or lacerti of the muscles, and which serves to support and to conduct them ; the smaller vessels or capillaries are not encircled by cellular tissue, but penetrate between the fibres, forming numerous capillary loops and meshes, having their long axes disposed in the direction of the length of the fibres. This arrangement of the capillaries is shown in Plate XLI. fig. 4.

Much of the colour of a muscle arises from the blood enclosed in the vessels, but not all, a portion of it being contained in the muscular fibres themselves.

It is evident that the contraction of the fibres exercises much influence upon the capillary circulation, reducing the calibre of the capillaries to such an extent as that the blood-corpuscles can pass through them only in an elongated form.

In the course of the larger vessels, imbedded in the inter-fascicular cellular tissue, fat corpuscles are often abundantly distributed, as represented in Plate XLI. fig. 1 .

Nerves of Muscles. — Muscles are also abundantly supplied with nerves, principally those of locomotion. Burdach has figured and

  • See Appendix, page 548.


362 THE SOLIDS.

described the nerves in muscles as forming loops, which either join other neighbouring loops or else return into themselves. The figure and description given by Burdach have been adopted by almost all succeeding anatomists ; notwithstanding which, I would observe, that I have never seen the nerves terminating in muscle in the manner indicated; not, however, that I doubt the fact of their doing so, because such a mode of termination is common to nerves; but would simply infer from this, that the loop-like arrangement is neither very general nor very obvious.

According, then, to the latest physiologists, nerves, strictly speaking, really have no termination whatever in muscles : an opinion, the accuracy of which is more than doubtful.

I find that the nerves, after branching in a dichotomous manner, have a real termination, and that from time to time certain tubules leave the main trunks, and end in the formation of elongated and ganglioniform organs situated between the fibres of muscle. (See Plate XLLJig. 4.)

UNION OF MUSCLE WITH TENDON.

The unstriped muscular fibrilla is rarely, if ever, attached to tendon or aponeurosis : the striped fibre, on the contrary, is almost constantly so.

Two errors have prevailed in reference to the union of the striated muscular fibre with tendon.

The first has reference to the form of the extremity of the fibre in connexion with the tendon; the second to the precise mode of junction between the two.

Thus, most observers have described and figured the fibre as terminating in a conical point, from which the fibres of the fibrous tissue of the tendon proceed in a straight line.

This description is contrary to fact, both as respects the form of the fibre and its mode of union with the tendon: muscular fibre is rarely, if ever, inserted vertically into a tendon or aponeurosis ; but in all the instances which have fallen under my observation, the insertion has been either oblique or occasionally at right angles with the tendon; the extremity of the fibre being in the one case also oblique, and in the other truncate : this termination is the very opposite of that usually attributed to it. Let us next see in what way the two structures are united. In no one instance have I ever seen the fibres of the fibrous tissue of the tendon unite themselves directly with the muscular fibre : on the contrary, the mode of junction has always


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been effected in the following manner: — the sheath of each fibre is prolonged upon the surface of the tendon where the union is oblique, and certain of the fibres of the tendon are extended upon and interlace with the terminal portions of the muscular fibres and their investing sheaths. (See Plate XLII. fig. 4.)

MUSCULAR CONTRACTION.

Many attempts have been made to determine the exact changes which the muscular fibre undergoes in its passage to a state of contraction; these attempts do not appear to me to be altogether satisfactory and successful.

The earliest opinion formed, in reference to muscular contraction, supposed that during contraction the fibres and fibrillae of muscle are disposed in a zigzag manner, such a disposition of the fibres of course having the effect of materially shortening the muscle. (Plate XLIII.

fig- 5.)

The advocates of this view seem to have overlooked the fact that fibres thus disposed, having no fixed or direct points from which to act, would have their power by such an arrangement rather diminished than increased: this idea has therefore been justly discarded, and an account of the nature of muscular contraction, much more closely approximating to the truth, substituted in its place.

Mr. Bowman, who has written by far the best account of muscular contraction which has yet appeared, discriminates between passive and active contraction of muscle : the former he conceives to be a uniform act, involving and affecting equally the entire mass of the muscle : the latter, on the other hand, he considers to be a partial act, implicating, first, a particular part or parts of a fibre ; subsequently leaving these, and advancing to other and neighbouring parts of the same fibre.

This view is founded principally upon the experiment detailed below, made upon a fibre of the claw of a crab, which still retained its contractility. "In an elementary fibre from the claw, laid out on glass, and then covered with a wet lamina of mica, the following phenomena are always to be observed: The ends become first contracted and fixed. Then contractions commence at isolated spots along the margin of the fibre, which they cause to bulge. At first they only engage a very limited amount of the mass, spreading into its interior equally in all directions, and being marked by a close approximation of the transverse stripes. These contractions pull


364 THE SOLIDS.

upon the remainder of the fibre only in the direction of its length; so that along its edge the transverse stripes in the intervals are very much widened and distorted. These contractions are never stationary, but oscillate from end to end, relinquishing on the one hand what they gain on the other. When they are numerous along the same margin, they interfere most irregularly with one another, dragging one another as though striving for the mastery, the larger ones continually overcoming the smaller; then subsiding, as though spent, stretched by new spots of contraction ; and again, after a short period of repose, engaged in their turn by some advancing wave. This is the first stage of the phenomenon. At a subsequent stage, the ends of the fibre commonly cease to be fixed, in consequence of the intermediate portions, by their contraction, receiving some of the pressure of the glass. The contractions, therefore, increasing in number and extent, gradually engage the whole substance of the fibre, which then is reduced to at least one-third of its original length."*

To this experiment, which I have never been able successfully to repeat, some exceptions may be taken. Thus, it is known that water has a powerful and remarkable effect in exciting muscular fibre which still retains its irritability to contraction, and the nodulated aspect of the fibre mentioned, may have been due to the fact that the fibre was not entirely immersed in water (the piece of mica being merely moistened), but only touched by that fluid at certain intervals, which most probably corresponded with the bulgings of the fibre referred to. This explanation is supported by the effect of water on recent muscular fibre, entirely immersed in that liquid. Thus, on the moment of immersion, the fibres contract greatly in length, increase in a corresponding proportion in bulk, become irregularly bulged and nodulated: the transverse lines on the fibres disappear, the longitudinal lines at the same time becoming more strongly marked than usual. (See Plate XLII. jig. 3.) These several effects are due to the extraordinary, unequal, and doubtless, also, abnormal contraction induced by the stimulus of water. Presuming, therefore, that in the experiment referred to, the phenomena occur in the order described, yet it would not be safe to adopt the conclusion, from this, that they represent the several stages of the normal contraction of a muscular fibre. Again, it might be argued, that the nodular condition described as belonging to a muscle in a state of active contraction would be most unfavourable for the full exercise of the power of contraction,

  • Physiological Anatomy, pp. 180,181.


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seeing that the nodules of one fibre would necessarily interfere with those of the contiguous fibres, and thus impede its own as well as their contraction.

For the above reasons, therefore, I would place but little reliance upon the experiment quoted, and prefer to adopt an explanation more simple in its character, and yet entirely sufficient to explain the condition of a muscle during its state of most active yet entirely normal contraction.

I conceive that no distinct line of demarcation exists whereby active and passive muscular contraction can be discriminated: the two are but different degrees of the same power, and manifest themselves by phenomena which differ not in kind, but simply in extent.

If a muscle of the leg of a frog be isolated from its fellows, or if the tongue of the same animal be extended and pinned to the margins of an aperture made in a piece of cork, the only change which can be observed to take place in the muscular fibre, when stimulated to contraction, consists in an approximation of its striae, neither waves nor nodules manifesting themselves in its course.

Again; immersion of muscular fibre, which has almost lost its contractile power in water, will be followed by an approximation of the striae, and a proportionate increase in the diameter of the filament.

Now, the approximation of the striae is the only visible sign which I have ever been able to detect in natural muscular contraction ; and it is amply sufficient to account for the shortening and increase in diameter which a muscle undergoes during its state of most active contraction.

The distance between the striae in a fibre placed somewhat on the stretch, as are all muscular fibres in their natural state, and in that which is in a state of contraction, varies greatly, and is very evident, the striae in the contracted fibre being often one-third or even onehalf closer together than they are in the fibre in its ordinary state of tension. The approximation of the striae to the extent just men-' tioned, presuming the entire length of the fibres to be in a contracted condition, would reduce the length of the muscle in the same proportion, viz: to the extent of a third or even one-half.

Muscular contraction, then, I would define to be a simple shortening of the fibres of a muscle, accompanied by an increase in their breadth ; this shortening in the striped muscular fibre being evinced by an approximation of the transverse striae, as well as by an increase in its diameter, while in the unstriped fibre it is manifested solely by an increase in the thickness of the fibrillae. (Plate XJAI.jig. 3. a, b.)


306 THE SOLIDS.

Whether, in muscular contraction, the whole length of the fibres of a muscle is engaged, or part only of their length, or whether, during the continuance of the contraction of a muscle, its fibres remain in a state of quiescence ; or whether they undergo an alternate contraction and relaxation, in obedience to the interrupted stimulus derived through the medium of the nerves, it is not easy to determine with certainty; nevertheless, it is most probable that where the contraction is very intense, and long sustained, such an alternation of condition does exist.

The stiffening of the body, which occurs after death, known by the terms "rigor mortis," "cadaveric rigidity," is due to muscular contraction. This rigidity usually comes on a few hours after death; and after continuing for a variable time, not exceeding six or seven days, again disappears. There is much variety, however, in the exact periods of the advent and departure of the rigidity: it has been observed to come on latest, attain its greatest intensity, and to last longest in the bodies of robust persons, who have either died of short and acute diseases, or who have suffered a violent death. On the contrary, it has been remarked to set in soonest, and to disappear earliest, in persons of feeble constitution, and those who have died of a lingering and exhausting malady.

The' immediate cause of cadaveric rigidity has never yet been satisfactorily explained. Some have supposed that it depends upon the coagulation of the blood in the capillaries — an hypothesis scarcely tenable: others, with more reason, conceive that it proceeds from the solidification of the fibrin of which muscle is chiefly constituted — that it is, in fact, a phenomenon precisely analogous to the coagulation of the fibrin of the blood.

An explanation differing from both of the former has suggested itself to my mind. I conceive that muscular contraction may possibly be brought about by the stimulus of the thinner and more watery parts of the blood, &c, acting on the still irritable muscular fibre, and which are known to escape from their containing vessels very shortly after the extinction of life. Of this passage of fluid through the walls of its receptacle, we have a familiar instance in the case of the gall-bladder and its contents.

Two other points require to be briefly alluded to, in relation to the subject of muscular contraction: the first is the muscular sound heard on applying the ear to a muscle in action, and which has been


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likened by Dr. Wollaston* to the distant rumbling of carriage-wheels ; the second relates to the fact made known by MM. Bequerel and Breschet, that a muscle during contraction experiences an augmentation of the temperature.

DEVELOPMENT OF MUSCLE.

The muscular tissue, like the majority of those which have hitherto been described, takes its origin in cells.

The term fibre is applicable only to the striped form of muscle, in which a number of fibrillse are included in an investing sheath common to them; these striped fibrillse of the striped fibre of voluntary muscles, are analogous to the unstriped fibrillse of the involuntary muscles.

The process of the development of muscle may be divided into three stages:

In the first, isolated cells, arranged in linear series, unite to form the unstriped fibrilla, the nuclei remaining.

This stage appertains to all unstriped muscular fibre.

In the second, the transverse striee or markings appear upon the fibrillse, the nuclei still remaining.

This stage is permanently exemplified in the muscles of the heart, temporarily in the voluntary muscles of the foetus, and probably also in some few other muscles.

In the third period, the fibrillse become very slender, the transverse markings more defined, and the nuclei altogether disappear.

This condition is represented in all the fully-developed striped muscles of animal life.

But the striped voluntary muscular fibre, even of the adult, constantly exhibits, and is constantly passing through the three stages just described ; a fact not generally known. It has been ascertained, indeed, since the time of Valentin, that the striped muscular fibre of the foetus originates in cells, and also that cell nuclei are contained in each fibre of the adult ; but it has not been perceived that the fibrillse also proceed from cells, and that the stage of muscular development, that of unstriped muscular fibre, likewise exists in the voluntary muscles of both the foetus and the adult.

It has been supposed, as we have already seen, that the nuclei which are met with in the striped muscular fibre are scattered throughout its entire thickness : this has been shown to be erroneous, and also that the nuclei are situated only on the exterior of each fibre.

  • Phil. Trans. 1811.


368 THE SOLIDS.

Now, in every adult striped muscular fibre, we find the nuclei under the following circumstances : some few of them are in a free state; others, more numerous, are contained in fibrillae, both striped and unstriped; of these fibrillae, the majority are on the inside of the sarcolemma; but some of them are also on its exterior, adhering to its surface, and constituting a considerable part of its substance: lastly, internal to these nucleated fibrillae, other fibrillae, which form the chief bulk of each fibre, exist destitute of nuclei.

With a good defining object-glass many of these unstriped fibres may be traced for a considerable distance along the fibre, and may be observed to contain as many as twenty nuclei. .

From these several facts it would thus appear, that striped and unstriped muscular fibre do not represent distinct types of structure, but that each is to be regarded as a different stage in the development of the same. The unstriped muscular fibrilla passes through but one stage of growth, and then its development becomes permanently arrested : the fibrillae of the heart, &c, attain a higher degree of development, the nucleated fibres becoming marked with transverse striae ; after which their growth permanently ceases : lastly, the striped fibrillae of the voluntary muscles reach the third and last period in the development of the muscular tissue, having their nuclei obliterated, and becoming exceedingly slender.

It would appear, also, that new fibrillae are constantly being developed, even in the adult muscular fibre.

But certain appearances may be observed which render it extremely probable that not merely new fibrillae are constantly being developed, but also that new fibres are continually being formed.

Thus, it is a common thing to meet with unstriped and even striped fibrillae, which are slightly adherent to the external surface of the sarcolemma ; again, small muscular fibres attached to the larger fibres, and consisting of but very few fibrillae, may constantly be observed. (Plate XLII. fig. 4.)

In the uterus we have a very remarkable example of a periodic development and subsequent absorption of unstriped muscular fibrillae.

The last point to which reference need be made is, to the doubt expressed as to "whether the identical corpuscles originally present" (in the fibre) "remain through life, or whether successive crops advance and decay during the progress of growth and nutrition."* This matter is no longer doubtful : the particulars observed in relation

  • Loc. eit, pp. 182, 183.


MUSCLE. .}".)

to the development of muscular fibre enable us to give a solution of the difficult v. Thus, there is no question but that successive crops of corpuscles or nuclei are continually being formed in both the striped and the unstriped muscles, and that those in the former are permanent, while in the latter they are only transitory.

It will be readily perceived that the above-detailed views of the structure and development of the muscular fibre differ, in very many important particulars, from those generally entertained. According to the views of most physiologists, the unstriped muscular fibre is the analogue of the striped fibre ; while, according to those of the author, the striped fibrilla is the analogue of the unstriped fibrilla, or "fibre" of most writers. Dr. Carpenter, in the third edition of the '•'Principles of Human Physiology," thus clearly gives expression to the notion that the striped and unstriped muscular fibres are the analogues of each other. "From the preceding history, it appears that there is no difference at an early stage of development between the striated and the non-striated forms of muscular fibre. Both are simple tubes, containing a granular matter, in which no definite arrangement can be traced, and presenting enlargements occasioned by the presence of the nuclei. But while the striated fibre goes on in its development, until the fibrilla?, with their alternation of light and dark spaces, are fully produced, the non-striated retains throughout life its original embryonic character." The description just quoted, in its application to the fibrillce of the striped and unstriped muscle, would be most true, but in its comparison of the unstriped fibrillar with the entire striped fibre, it is completely at fault.

There is considerable discrepancy between the views entertained by Bowman and Valentin, and those expressed in this work, in relation to the development of muscle, as will be evident from the statement of them by the former gentleman. "The researches of Valentin and Schwann have shown that a muscle consists, in the earliest stage, of a mass of nucleated cells, which first arrange themselves in a linear series, with more or less regularity, and then unite to constitute the elementary fibres. As this process of the union of the cells is going forward, a deposit of contractile material gradually takes place within them, commencing on the inner surface, and advancing towards the centre, till the whole is solidified. The deposition occurs in granules, which, as they come into view, are seen to be disposed in the utmost order, according to the two directions already specified. These granules or sarcous elements being of the same size as in the perfect

24


370 THE SOLIDS.

muscle, the transverse stripes resulting from their opposition are of the same width as in the adult; but as they are very few in number, the fibres which they compose are of corresponding tenuity. From the very first moment of their formation these granules are parts of a mass, and not independent of one another; for, as soon as solid matter is deposited in the cells, faint indications of a regular arrangement in granules are usually to be met with. It is common for the longitudinal lines to become well defined before the transverse ones: when both are become strongly marked, as is always the case at birth, the nuclei of the cells, which were before visible, disappear from view, being shrouded by the dark shadows caused by the multitudinous refractions of the light transmitted through the mass of granules ; but they can still be shown to exist in the perfect fibre, in all animals, and at all periods of life, by immersion in a weak acid; which, while it swells the fibrous material of the granules, and obliterates their intervening lines, has no action on the nuclei."

According to the views entertained by the author, a striated muscular fibre, in the earliest period of its development, consists of cells arranged in linear series : these unite together, giving origin to the fibrilla and not the fibre, and that each fibrilla of a fibre is, in like manner, developed from cells.

Dr. Sharpey, in the fifth edition of Quain's "Anatomy," makes the remark, in treating of the subject of the development of muscle, " But much still remains to be explained by future investigation." The truth of this remark it is conceived is, in some degree, exemplified in the foregoing article on muscular fibre.


MUSCLE.


371


MUSCLE.

[To what the striation of muscular fibre is owing, is not yet satisfactorily established. The opinion of Drs. Sharpey and Carpenter, again referred to in the Appendix, and seemingly adopted by the author, that the striation, or dark spots on the fibrillse, indicate the cavities of the cells which compose each fibrilla, is more probably the correct explanation. The junctions of these cells, according to the same authorities, are further marked by delicate transverse lines, intermediate between the cells. These lines are readily seen in the muscular fibre of the pig, with a power of 600 diameters.

That the striation depends on the corrugation of the muscular fibre, a theory which the author seemed disposed to adopt in his explanation of Plate XLIIL, fig. 6, is not probable. The striations are too regular to result from such cause.

Professor Kolliker has ascertained that non-striated muscular fibre more generally enters into the structure of different organs, than was usually believed. His researches on this subject have been very laborious, and an abstract of the results obtained by him has been published in the eleventh number of the "British and Foreign Medico-Chirugical Review," for July 1850. This abstract is so clear and concise, and affords such assistance to the student, that it is here inserted.

ON A NEW FORM OF SMOOTH OR NON-STRIATED MUSCULAR FIBRE. BY PROFESSOR KOLLIKER.

"Kolliker describes the smooth muscles as composed of short, isolated fibres, each containing a nucleus. He calls them muscular or contractile fibre-cells, and gives three varieties:

1. "Short, round, spindle-shaped, or rectangular plates, like those of epithelium, 0-01"' long, and 0-006"' broad.

2. " Long plates of irregular rectangular, spindle or club-like shape, with fringed edges, 0-02'" long, and 0-001'" broad.

3. " Narrow, spindle-shaped, round, or flat fibre, with fine ends, which are either straight or wavy, 0-02'", or even 0-25'" long, and 0-002'" to 0'01'" broad.

" The first and second of these forms are only to be found in the walls of vessels ; the first may be mistaken for the cells of epithelium.

"These muscular fibre-cells are composed of soft, light yellow substance, which swells in water and acetic acid, in which last it becomes of a paler colour. There is no appreciable difference between the outer and inner parts, though in acetic acid it would seem as if each fibre-cell had a delicate covering. Their substance is homogeneous, with longitudinal stripes ; and they often contain small pale granules, sometimes yellow globules of fat. Each fibre-cell has without exception a pale nucleus, sometimes only perceptible in acetic acid. Its form is peculiar, being like a small staff rounded at each end. The substance of the nucleus is homogeneous; its length is 0-006'" —0-004'", its breadth 0-0008" —0-00013'". The muscular fibre-cells lying side by side, or end to end, form the smooth muscles as they appear to the naked eye. They may be divided into:


£72 THE SOLIDS.

1. "Purely smooth muscles containing no other tissue; such are those of the nipple, corium, of the interior of the eye, of the intestines, of the perspiratory glands of the axilla, of the cerumen glands ot the ear, of the bladder, of the prostate, of the vagina, of the small arteries, of the veins and lymphatics.

2. "Mixed smooth muscles, which contain, besides the muscular fibre-cells, cellular tissue, nuclear fibre, and elastic fibre: such are the trabecula? of the spleen and corpora cavernosa of both sexes. They are also found in the tunica dartos, gallducts, the fibres of the trigonum vesicae, the circular fibres of the larger arteries and veins, the long and transverse fibres of the prostata, urethra, Fallopian tubes, and of the womb: they change by imperceptible transitions into the first form; this is the case in the trachea, bronchi, urethra, the inner muscular layer of the testicles, seminal ducts, &c.

"Kolliker says, that he has found smooth muscles in the skin to a far greater extent than is generally supposed. In the sub-cutaneous cellular membrane of the scrotum, penis (prepuce), and the anterior portion of the perineum, they are well developed. The greater number seems to exist in the tunica dartos; in the perineum and prepuce there are fewer. In the tunica dartos they form a muscular coat resembling, on a small scale, the tissue of the bladder. In the nipple and areola (especially in the female), the smooth muscles are strongly developed, somewhat resembling those of the tunica dartos, but having no fibrous covering. In the areola, up to the base of the nipple, they are arranged in circular order; in the nipple they are circular and vertical, the ducts passing between them. Some lie in the corium, and form the corpus reticulare; others belong to the sub-cutaneous tissue. Smooth muscles are also found in every part of the body covered with hair, in the hair-bulb, and in the upper portion of the corium. In the parts not covered with hair, such as the palm of the hand, the smooth muscles are wanting. One or two bundles of muscular fibre encircle each hair-bulb or sebaceous gland. Kolliker remarks, that the tensor choroidese does not insert itself into the processus ciliaris, but that it lies fiat on its anterior surface, and that it arises from the canalis schlemmii. The sphincter pupillae, he says, may be easily seen in the eye of the white rabbit, and in the blue eye in man, on removing the uvea. In man it is \'" broad, and forms the pupillar edge of the iris. He has also observed a muscular ring near the annulus iridis minor. The dilator pupillse does not form a continuous membrane, but seems to consist of isolated bundles of fibres passing between the muscles to insert themselves in the edge of the sphincter. He has never seen the anastomosis of these fibres mentioned by Todd and Bowman. The writer thinks that the elements of all these muscles are smooth muscular fibre, thougli he admits that he has seldom succeeded in isolating the muscular fibre-cells in the human body. He does not think that the M. cochlearis discovered in the ear by Todd and Bowman deserves the name of a muscle; he is rather disposed to consider it as a ligamentous structure, and calls it the ligamentum spirale; he looks upon it as a means of attachment for the zonula membranacea. Remarking that the smooth muscles of the intestines resemble one another in their histological characters, he points out one peculiarity, viz : that they present a knotty appearance with ends running out into fine spirals. He thinks that it is not improbable that the knots are due to a contraction of the fibre. The fibrecells of the intestine seem to be striped, as if they were composed of an envelope and some homogeneous striped contents. No muscular fibre is found among them, but they are covered and bound together by cellular membrane.


MUSCLE. 373

" The small perspiratory glands seldom possess smooth muscular fibres, although these are always present in the large perspiratory glands of the axilla, and in the cerumen glands of the ear.

"Kolliker does not admit the presence of muscular fibre in the lacteal glands. "In the lungs he finds that the structure of the small and large bronchi is the same. Outside of the epithelium they present a layer composed of longitudinal fibres of areolar tissue, and a number of strong, fine, elastic fibres. Then follow one or more circular layers of smooth muscular fibre, with some nuclear fibre running transversely ; lastly, a layer of cellular tissue, with nuclear fibre. He never could find muscular fibre running longitudinally through the bronchi. With respect to the vesicles of the lungs, he could come to no satisfactory conclusion. Long nuclei are seen in the walls of the vesicles, but they are not so long and narrow as those of the smooth muscles, and appear to him to belong to the capillaries. The smooth muscles of the trachea and bronchi resemble in their elements those of the intestines. In the ox, the gall-bladder, the ductus cysticus, d. choledocus, and the ducts lying out of the substance of the liver, present a large amount of muscular fibre of the smooth species. It is strongly developed in the canals, in which it is so disposed longitudinally; in the gall-bladder this is not so much the case, a transverse, and even an oblique layer of the fibres being placed between two longitudinal layers. In the human body, the muscular structure is very faintly developed in the gall-ducts. Kolliker could only discover a very delicate layer at all approaching muscular fibre. In the pancreatic ducts of the human body, no trace of muscular fibre exists. In the lacrymal apparatus there are no muscular fibres: in the ductus stenonianus none; the ductus whartonianus has a very faint layer of smooth muscular fibre.

"No part of the internal structure of the kidney shows traces of museular fibre; it is only in the calices and pelves that it becomes apparent. The muscular fibres of the pelves and calices are composed of an outer longitudinal coat, and an inner transversal layer; they are continuations of the same in the urethra, and all partake of the general characters of smooth muscular fibre. Supposing the disposition of the muscular fibres of the bladder to be well known, the writer observes that the trigonum vesicas consists of a pretty strong layer of pale yellow fibres immediately under the mucous membrane; this is to be considered as an expansion of the longitudinal fibres of the urethra.

" The canaliculi of the testes have no muscular fibres, but on the inner side of the interior surface of the tunica vaginalis communis, smooth muscular fibre is evident. The vas deferens presents a thick layer of smooth muscular fibre, forming an outer longitudinal, a middle transverse, and an oblique layer directly under the mucous membrane. The canaliculi of the epididymis present the same conditions of their walls as the vasa deferentia. Kolliker thinks he has seen some muscular fibres in the body of the epididymis. The ductus ejaculatorii are formed like the vas deferens ; the seminal vesicles present also the same conditions. Both coverings of the prostate — that derived from the seminal vesicles, and its own peculiar covering — are more or less muscular.

" The pars membranacea urethrae possesses but little smooth fibre, compared with the prostate. Under the mucous membrane (whose cellular tissue is rich in elastic or nucleus-fibre) there is a layer of longitudinal fibre, mostly composed of fibrocellular membrane, containing nuclear fibre and contractile fibre-cells: this layer is


374 THE SOLIDS.

succeeded by another of transverse fibre belonging to the musculus urethralis; it also contains smooth muscular fibre. In the pars cavernosa urethra the fibres are but slightly developed; but they are still found at a certain depth.

"The corpora cavernosa may be considered as highly developed muscular structures, furnished with peculiar blood-vessels, since the smooth muscular fibres exist in the fibrous septa, even in the glans.

" The inner portions of the uropoietic viscera in the female resemble those of the male witli regard to their structure. The urethra has, besides the longitudinal fibres, a transverse layer of smooth muscular fibre. Fallopian tubes have a thick, middle layer of longitudinal and transverse fibre ; the elements of which are smooth muscular fibre-cells, with moderate-sized nuclei. The smooth muscular fibre is with difficulty isolated in the virgin state ; but in the gravid uterus it is seen in great perfection. In the fifth month Kolliker saw bundles of red fibre of the smooth muscular kind, mixed with cellular membrane, without nucleated fibre; the fibre-cells were spindle-shaped, and very long. As pregnancy advances, no new cells seem to form; but those already formed increase in size. Sometimes they measure j^" ' -\" ' ', they are spindle-shaped, and ran out into long, thin tails. After birth, they rapidly decrease in size. The middle or vascular layer of the uterus is rich in smooth muscular fibre; it differs only from the inner and outer coat, in the fibres crossing each other in every direction.

" The ligamenta uteri anteriora et posteriora present a red fibrous tissue, enclosed in the two folds of the peritoneum; in this, smooth muscular fibre maybe traced. In the ligamenta ovarii very few are found. The writer says he has seen muscular fibre in the lower portion of the anterior fold of the peritoneum; on the ligamenta lata these fibres expand between the folds, and he even thinks that they insert themselves in the walls of the pelvis. Directly under the mucous membrane of the vagina, a layer of muscular fibre exists, stretching from the bottom of the vagina to the vestibule, and containing a thick plexus of veins; it is composed of longitudinal, but more especially of transverse, long fibre-cells, with wavy ends. The structure of the clitoris, glans clitoridis, bulbus vestibuli, &c, is analogous to that of the corpora cavernosa in the male.

"In the spleen of the human body, Kolliker has never been able to discover smooth muscular fibre, either in its covering, or in the larger fibrous bands; but in the microscopical fibrous bands he has found elements which he thinks are of a muscular nature. He also states, that in birds, reptiles, and fishes he has found some muscular fibre in the fibrous bands of the spleen. The existence of smooth muscular fibre in the blood-vessels and lymphatics is indubitable; Kolliker recommends the middle-sized arteries and veins for examination. In the aorta and trunks of the pulmonary arteries, the middle coat is composed alternately of muscular and elastic membrane, with fibro-cellular tissue. These muscles consist of fibre-cells, containing nuclei. The larger veins of the human body present, externally to their lining, a single or double layer of elastic fibre, a simple coat of transverse muscular fibre-cells, mixed with cellular tissue, to which succeeds externally a coat of longitudinal fibres. In the middle-sized veins there is a middle coat of a pale reddish colour, composed of alternate transverse and longitudinal fibres; the former are of fibro-cellular tissue and contractile fibre-cells. Towards the periphery, the muscular structure decreases. The veins of the uterus, which in the unimpregnated state present no peculiarities.


MUSCLE. 375

acquire a great development during pregnancy with regard to length and organization. This does not so much proceed from the thickening of their walls, as from the increasing size of the fibre-cells existing in the middle coat before pregnancy, and in certain changes in the outer and inner coat caused by their acquiring a considerable quantity of smooth muscular fibre. The very large veins which pierce the inner muscular coat of the uterus at the point of attachment of the placenta, and which communicate with its uterine portion, make an exception to this rule, as they have only longitudinal muscular coats, which with the epithelium form the walls of the vein.

"The following veins have no muscular structure:

1. " The veins of the uterine portion of the placenta.

2. "The veins of the cerebral substance, which are formed of epithelium and cellular membrane.

3. " The sinuses of the dura mater.

4. "Breschet's veins of the bones.

5. "The venous cells of the corpora cavernosa in the male and female.

6. "Probably the venous cells ef the spleen. The muscular fibres of the lymphatics are like those of the veins, they exist sparingly in the trunks, and in greater number in the smaller branches."

MANIPULATION.

Muscular fibre is best studied by placing a small fragment of muscle on a glass slide, moistening it with water, and tearing it with fine needles, until the fibrillse are made apparent.

The sarcolemma or sheath of muscular fibre may be displayed on rupturing the fibrillse by tension ; the sarcolemma will sometimes remain unbroken after the fibrillse are ruptured, and may thus be examined. Another method is to immerse the fibre in water before irritability be extinguished ; the fibre imbibes the moisture, then contracts, and presses out the fluid which raises the sheath into vesicles.

The study of the muscular fibre in the inferior animals is replete with interest, the largest fibres being found in fishes and reptiles. In the lobster and shrimp, the fibrillas are well seen, even after they have been boiled.

The muscular fibre of the pig is worthy of examination; it is so capable of being resolved into oblong squares by sufficient magnifying power, that it has been adopted as a test for object glasses of high power.

Mr. Quekett states that the nerves of muscular fibre are best studied in the thin layer of muscle, which forms part of the abdominal wall of the frog. Some of the capillary vessels maybe also here seen: these vessels, however, are best observed after they have been filled with fine injection when their relation to the primary fasciculi can be made apparent.

Muscular fibre, whether injected or not, is best preserved in fluid, in flat or thin glass cells, so it may be examined with high powers.]


376


THE SOLIDS.

Article XIX. — Nerves

The nervous system has been divided into two orders or lesser systems; the cerebro-spinal, which includes the brain and spinal cord, together with the nerves which proceed therefrom, and the sympathetic systems. The former, which admits of still further leading divisions, presides over animal life, its nerves administering to sensation, and being distributed to the principal organs of locomotion, the muscles, as well as to those of the senses; the latter is connected with the functions of organic life, and supplies principally the viscera and glands with nerves.

Corresponding with the presumed functional differences of the two systems, there are also certain structural differences, the nature of which will shortly be described.


STRUCTURE OF NERVES.


Cerebro-spinae System. — The nervous matter constituting the cerebro-spinal system consists of two very distinct substances, a gray, cineritious, cellular, or secreting structure, and a white, conducting, or tubular structure.

Secreting or Cellular Structure. — The very numerous situations in which the gray matter of the brain and spinal cord is encountered need not here be described at any length: it will be sufficient to observe, that in the cerebrum it occupies principally an external situation, a layer of it of about the one-eighth of an inch in thickness, extending over the entire surface of its convolutions; but that it is also found in lesser quantities in several localities in the interior of the cerebrum, as in the optic thalami, corpora striata, tuber cinereum, crura cerebri, &c; that, on the other hand, in the cerebellum, pons Varollii, medulla oblongata, and spinal cord, it is deep seated, forming the central portion of these organs.

The secreting substance, or gray matter of the brain, is made up of a granular base, in which are contained numerous nucleated cells of different sizes and forms. In the gray matter of the convolutions of the brain the granular base is very abundant, the cells small and round, and in less proportion than the base itself: in the tuber cinereum, in the cerebellum, and in the gray matter of the cord, the small granular cells are extremely abundant, and the granular base is diminished in quantity. (See Plate XLV. figs. 2, 3.) ■


NERVES. 377

Now, the granular base and the small granular cells constitute the principal portion of the substance of the gray matter, whereverencountered: in certain localities, however, cells of different forms and of considerable magnitude are met with: these cells have been termed ganglion cells.

Ganglion Cells. — Ganglion cells are encountered in different portions of the cerebro-spinal system, as in the locus niger of the crura cerebri, in the gray matter of the arbor vitas, and corpus dentatum of the cerebellum; in the medulla oblongata; in the spinal cord for its entire length, and according to Valentin and Purkinje, in all the extent of the cerebral hemispheres, especially in the posterior lobes, and in the gray lamina of the spiral fold of the cornu Ammonis.

These cells vary greatly both in size and shape; many of them attain a very considerable diameter, and they are, almost without exception, all provided with caudate prolongations, which are frequently branched. (See Plate XLIV. fig. 4.)

The ganglioniform cells of the locus niger are for the most part small, and irregularly stelliform in shape: those of the gray matter of the cerebellum are pyriform, the spinous and often-branched processes, usually two or three in number, proceeding from their narrow extremities: many of the cells of the medulla oblongata are triangular, the spines arising from the angles, and being much produced, those of the spinal cord are usually very large, irregular in form, and are furnished with numerous prolongations.

These cells are highly and uniformly granular: they frequently contain pigmentary matter, and enclose a nucleus, which again is provided with its nucleolus, and both of which are remarkable for their exceeding brilliancy.

Ganglion cells are, doubtless, connected with the secretion of the nervous element or fluid : the use of the prolongations with which they are furnished, and the precise relation of these with the adjacent structures, the smaller secreting cells and the nerve tubules, is not yet well ascertained: it has been conjectured, however, that the caudiform processes are directly continuous with the tubules ; a view which is certainly incorrect.

Mixed up with the ganglion cells wherever met with, but especially' with those occurring in the gray matter of the cerebellum and spinal cord, a considerable number of branched and nucleated fibres may be seen, similar in appearance and structure to those of unstriped muscle, and more particularly resembling the gelatinous filaments of the sympathetic system, from which they in all probability really proceed.


378 THE SOLIDS.

There is a second description of ganglion cell, not contained in either the brain or spinal cord, but found in the various ganglia, as the Casserian, Optic, Ophthalmic, Spinal, &c, formed in connexion with the nerves of the cerebro-spinal and sympathetic systems, and which may be here described.

These cells resemble the ganglion corpuscles already noticed in their general structure, but differ from them in form, being more or less round in shape, and destitute of the branched processes belonging to the latter. (See Plate XLV. fig. 4.)

The mode of multiplication of ganglion cells is not well understood : it is possible that the numerous granules contained in each are the germs of the future cells Adhering to the surface of many of the larger ganglion cells of the second form, a number of nucleated particles or lesser cells may frequently be observed, forming a kind of capsule around them, which, however, is entirely external to the proper membrane of the cells. (See Plate XLV. fig. 4.)

Tubular Structure. — The white fibrous substance of the brain, spinal cord, the nerves of motion and of special sensation, is composed of unbranched tubules, the diameter of which is subject to considerable variation. The tubules of the cerebrum are exceedingly slender, as are also those of the nerves of special sense : those of the cerebellum, spinal cord, posterior root of spinal nerves, and of the sympathetic system, are of somewhat larger calibre, while those of the motor nerves are of still larger size, and of firmer texture. See the figures. The tubules of the white substance of the cerebrum are especially prone to become dilated at intervals, or varicose. (See Plate XLIV. fig. 7.) This condition was formerly supposed to be natural, and it was presumed that by this character the nerves of special sense could be discriminated from those of motion: there is little doubt, however, but that this varicose condition of the fibres is abnormal, and that it is produced by the pressure and disturbance to which they are subject during examination. The tubules of the cerebellum are subject to a like change, although in a less degree; those of the nerves of motion are but little prone to the alteration, these becoming, when much disturbed, broken into fragments, many of which assume a globular form, and all of which are greatly corrugated. (See Plate XUY. fig. 1.)

The nerve tubules contain a fluid matter, and it is the collection of this fluid in certain parts of each tubule, the result of pressure, which occasions the distension of the membranous wall of the tubes.


NERVES. 3T9

and which gives rise to the varicose condition described. Such is, at least, the most probable explanation of the exact nature of this condition.

The tubules of the cerebrum, cerebellum, spinal cord, and motor nerves, &c, present an average diameter: nevertheless, much difference may be detected in the size of the tubules taken from the same portion of the nervous system : those of the spinal cord agree in their average size with those of the cerebellum.

The tubes of the cerebrum, of the nerves of special sense, and of the cerebellum, are so small, that it is impossible to ascertain with certainty the amount of organization which really belongs to them : this, however, is not the case with those of the motor nerves, which are so much larger. (See Plate XLIV. jig. 1.)

Each tube of a motor nerve consists of an investing sheath or neurilemma, an inner elastic and but little consistent matter, the "white substance of Schwann," which forms a pseudo membrane, and which includes the third constituent of the nerve tube, a soft and semi-fluid matter, which, however, would appear in some cases to become solid, and to exhibit a fibrous fracture: this matter has been termed the "axis cylinder."

It is a matter of some difficulty to display the investing sheath, or neurilemma, around the fibres in their fresh and unaltered state: it may, however, be easily detected, and its structure 'recognised in a portion of motor nerve which has been immersed for some hours in spirit : it will then be seen that it is made up of nucleated fibres, the nuclei in the sheath of fcetal nerve tubes being of considerable size, and presenting a smooth aspect. (See Plate XLIV. jig. 2.)

Todd and Bowman describe the outer membrane of the nerve tube, and to which alone the word neurilemma should be applied, "as an homogenous and probably elastic tissue of extreme delicacy, analogous to the sarcolemma of striped muscle, and, according to our observation, not presenting any such distinct longitudinal or oblique fibres in its composition as have been described by some writers." It will be observed that this description does not accord with that given by the author.

The white substance of Schwann, on the contrary, is best seen in the motor nerve tubes, which are perfectly recent, and which have been but little disturbed : its thickness is indicated by a double line which runs along each side of the tube : it does not present any trace of organization : it is very elastic, and its contraction gives rise to the


380 THE SOLIDS.

corrugated appearance presented by the tubes of motor nerves which have been disturbed and broken. (Plate XLIV. fig. 1.)

The existence of -the third constituent of the nerve tube, the "axis cylinder" of Rosenthal and Purkinje, is best determined by the immersion of the fibres in either ether or acetic acid, which breaks it up into granules and vesicles. (Plate HJAV.fig. 3.)

In albumen the nerve tubes and nervous tissue in general undergo but little alteration, and it is therefore in this fluid that its examination is best conducted.

But the tubes of the white fibrous material of the cerebrum, cerebellum, and spinal marrow, just described, form one element only of its structure; another is invariably present, forming indeed the greater portion of its substance; and it is somewhat strange that it should have been overlooked by observers: this element consists of globules of every possible size, which, when free from pressure and undisturbed, are perfectly spherical, but which are put out of shape by the slightest compression or disturbance. It is not easy to determine whether these globules are true cells or not: they present the greatest possible variety of size : they have the colour and consistence of oil; but nevertheless appear to be hollow, and frequently present a spot which bears much resemblance to a nucleus. (See Plate XLIV. fig. 6.)

It now only remains to be observed, that the nerves of special sense, as the optic, olfactory, and auditory, present a structure precisely analogous to that of the white substance of the cerebrum.

Sympathetic System. — The nerves entering into the formation of the sympathetic or organic system, differ both in appearance and structure from those derived from the cerebro- spinal system: thus, the great sympathetic cord itself, as well as the organic nerves connected with it, present a reddish gray colour, are soft and gelatinous, and do not readily admit of division in the longitudinal direction, although they are easily torn across by any extending force : these differences of colour and of consistence are dependent upon a difference of structure. The great sympathetic cord itself, and the organic nerves connected with it, are composed of two distinct descriptions of fibre; first, of the ordinary tubular fibre, which, however, is of small diameter, and therefore readily becomes varicose, and second, of nucleated filaments, in every appreciable respect resembling those of unstriped muscular fibre. Henle has called these fibres "gelatinous nerve fibres."


NERVES. 381

The relative proportions existing between these two kinds of fibre differ in different nerves : thus, in some cases, the gelatinous fibres are by far the most numerous ; in others, the tubular fibres preponderate. The gelatinous or gray filaments are best seen in what are called the roots of the sympathetic ; that is to say, in the branches which, accompanying the carotid artery, proceed from the superior cervical ganglion to the fifth and sixth pair of cerebral nerves, and in those which descend from the same ganglion and follow the course of the carotid. In these the proportion of tubular fibres' is but small, as one to six; and they are also isolated from each other, each being surrounded with a number of gelatinous fibres. This disposition of the nucleated fibres has led Valentin to consider that they form a sheath around the tubular fibres, each gray nerve, according to that observer, being composed of a number of fascicles or bundles. Henle, however, objects to this view, considering that the fibres are too large for a sheath, and remarking that the gray nerves do not separate into such bundles, but divide much more readily in such a way as that the tubular fibre, is found at the border of the bundle. Henle, therefore, considers it to be more natural to regard the gray nerves as forming solid threads, composed of nucleated filaments, between which the tubular fibres run.

The tubular fibres are more numerous than in the roots of the great sympathetic, in the majority of the visceral nerves, in the branches which proceed from the cardiac and hypo-gastric plexuses, &c; in these the tubular fibres may be seen enclosed within the gray filaments, forming many bundles. Their number becomes still more considerable in the great sympathetic cord itself and the splanchnic nerves; the cardiac nerves are almost entirely formed of tubular fibres. In all these nerves the tubular fibres are observed to be of smaller diameter than they are in those which are distributed to the voluntary muscles.

In consequence of the great difference which exists between the structure of the tubular nerve fibre and that of the gelatinous nerve fibre, it has been a matter of doubt with some observers whether the latter should be regarded as a true nerve fibre or not.

The following is a brief enumeration of the various anatomical and microscopical facts hitherto recorded, both in favour of and opposed to the opinion of the nervous character of the gelatinous filaments just described.

The chief structural considerations which may be urged in favour


382 THE SOLIDS.

of the opinion that the nucleated filaments associated with the various nerves of the sympathetic system are true nerve filaments are —

1st. The origin of the gelatinous filaments from the ganglia of the sympathetic, as first distinctly affirmed in the researches of Volkmann and Bidder.*

2d. The tubular character of these filaments, as shown by T. Wharton Jones. f

3d. The peripheral distribution of the gelatinous filaments, as asserted by many observers, but particularly by Bidder, who even states that he succeeded in counting their number in the transparent septum of the auricles of the frog's heart.

4th. The peculiar structure of the ganglion caecum, discovered by Mr. T. Wharton Jones, in connexion with one of the ciliary nerves of the dog. J

5th. The variable, yet fixed proportions of gelatinous and tubular fibres occurring in different nerves, as described especially by Henle.

6th. The occurrence, as stated by Todd and Bowman, of nucleated filaments very similar to the gelatinous fibres of the sympathetic, "in parts where their nervous character is indubitable, as in the olfactory filaments, and the nerve in the axis of the Pacinian corpuscle, exhibits very much the same appearance, save that it is devoid of nuclei. "§

7th. The resemblance borne, according to the observations of Schwann, || between the tubular nerve fibre in the early stages of its development, in which it is described as being nucleated, and the adult gelatinous fibre.

8th. The origin of the gelatinous filaments from the cells themselves composing the ganglia of the sympathetic, as the observations of several observers tend to prove.

These various facts thus briefly referred to, could they all be fully depended upon, would, doubtless, make out not merely a strong, but even a convincing and unanswerable case in favour of the nervous character of the gelatinous filaments: unfortunately, however, those facts which, if they could be relied upon, would be the most conclusive, are open to question: such, for instance, as the peripheral distribution of the gelatinous filaments, their presumed origin from

  • Die Selbstandigkeit des Sympathislten Nervensyslems durch Analomische Untersuchungen nachgewiesen Von J. H. Bidder und A. W. W. Volkmann. Leipsig, 1842.

f Lancet, April 24th, 1847. \ Lancet, November 14th, 1846.

§ Physiological Anatomy, part hi. p. 142. 11 See Wagner's Physiology, translation by Willis.


NERVES. 383

the ganglionic corpuscles, and the asserted resemblance between the tubular nerve fibre in an early stage of its development and the fullygrown gelatinous filament: it will presently be shown, indeed, in the observations on the growth of the primitive nerve tubule, that no such resemblance exists.

Subtracting, then, the points referred to in the 3d, 7th. and 8th headings, no one conclusive fact remains of the position that the gelatinous fibres are really nervous.

Against the opinion that the gelatinous filaments are nervous, may be urged :

1st. The positive structural identity between the gelatinous nerve filament and the fibrilla of unstriped muscle, and the great improbability, as a consequence, that one and the same structure should have to perform two such distinct functions as must necessarily belong to a muscular fibre and a nerve tube.

2d. The apparent structural unfitness of nucleated filaments to serve as a conducting medium of the nervous force.

3d. The evidently tubular character of the nerve filaments in parts which, from their nature, we should expect would be preeminently supplied by the gelatinous filaments.

4th. The fact of the non-occurrence of gelatinous fibres, separate from the tubular, is strongly opposed to the idea of the independence of the former.

The above short summary will serve to give some idea of the state of the much-canvassed question of the nervous or non-nervous character of the gray or gelatinous filaments of the sympathetic.

STRUCTURE OF GANGLIA.

The ganglia consist of the peculiar globules already described, of nerve tubules, and of gelatinous filaments.

Each ganglion is enclosed in an investing tunic of fibrous tissue? a continuation of the common envelope of the nerves which enter and depart from it, and which sends down dissepiments which divide the contained globules into parcels, and thereby give the ganglion the general arrangement and character of a gland.

The gelatinous nerve filaments in the ganglion form a kind of inner capsule, and their arrangement is thus described by Henle: "Besides the nervous fibres properly so called of the soft nerves, one meets with also, in the ganglions of the great sympathetic, gelatinous fibres which have special relations with the ganglionic globules. The fibres


384 THE SOLIDS.

of a bundle expand in the form of a funnel, in order to embrace a globule or a series of globules, and unite together afterwards afresh, to separate again a second time. In this way we often come to draw out of a ganglion entire threads of gelatinous fibres, which are dilated, in the manner of a chain of pearls, and enclosing the globules in their dilatations."

The proper tubular fibres enter the divisions of the ganglion in bundles, subsequently separate from each other, and ramify among the ganglion globules in a waved and serpentine manner.

The arrangement of the ganglion globules and nerve tubules just indicated, tends to show that these are really the only essential elements of a ganglion.

The ganglia are supplied with blood-vessels.

It will be apparent from the above description that the ganglia have all the structural characteristics of glands, and therefore there can be little question but that they are really glandular organs, and that the tubular fibres which pass through them carry away the fluid, which is destined to exercise its influence on the parts and organs to which the nerves are themselves distributed.

The question as to the origin of either the. tubular fibre or the gelatinous filament from the ganglionary corpuscles, is still an undecided one, the weight of evidence being opposed to the idea that either order of fibres has any origin from these corpuscles.

ORIGIN AND TERMINATION OF NERVES.

Origin. — But little that is certain is known respecting the exact mode of origin of the numerous tubules composing the nerves, and of the precise relation of these with the cellular or secreting element of the ganglionic centres. The observations of Dr. Lonsdale,* however, render it highly probable that the greater portion at least of the nerve tubes have a looped origin in the brain and spinal cord : that gentleman having made out the interesting fact, that in two fetuses, in the one of which both the brain and spinal cord were deficient, and in the other the brain only, the extremities of the nerves, which extended into the cavities of the spinal column and cranium, were made up of looped nerve tubes imbedded in an imperfectly developed granular and cellular matter, apparently of a ganglionic character. Now, from what is known respecting the laws of development, it would appear to

  • Edinburgh Medical and Surgical Journal, No. cxvii.


NERVES. 3S">

be a perfectly justifiable and natural inference, that the nerve tubes, when fully developed, have a similar mode of origin.

According to some observers, certain nerve tubes are connected with and take their origin from the prolongations with which the caudate variety of ganglionary cells are provided ; this view, however, is confidently denied by many other investigators, and the point is one which is still involved in considerable uncertainty : for myself, I would observe, that I have never succeeded in making a single observation favourable to such a conclusion. Notwithstanding, however, the doubts which are now entertained respecting the modes of origin of nerve tubes, the question is assuredly one which, at some future day, will be satisfactorily determined by direct observation.

It is also still uncertain whether nerve tubules originate in the ganglia not included in the brain, as in those connected with the encephalic nerves, and those of the sympathetic system.

When speaking in the preceding remarks of the origin of nerves, that extremity of them is implied which is in connexion with the brain and spinal cord: it is questionable, however, in the case of the nerves of special sense, whether it would not be more proper to consider their peripheral rather than their central extremities as their true origins; a view supported by the consideration that the .sensations arise in, and proceed from, the organs of the senses inwards towards the brain, the great centre of nervous structure and force, as well as by the fact, that the peripheral extremities of these nerves are generally, if not invariably, connected with ganglionic cells; such an association of the two elements is known to exist in the eye, in the ear, in the nose, and probably exists also in the papillae of the tongue and skin.

Termination. — It was not known until within the last four or five years that nerves had any real termination: it was up to that time generally considered that the nerve tubes invariably ended in the same manner as it is now supposed that they originate, viz : in loops ; and there can be little question but that such a mode of termination, though not universal, is at least very frequent: thus, the arrangement of the primitive nerve fibres in loops has been described by Valentin, in the pulps of the teeth; by Muller, in the membrana nictitans, and in the mucous membrane of the throat of the frog; in the papillae of the skin and tongue, by Todd and Bowman. The loops are formed by one or more of the nerve tubes, separating themselves from the bundle of tubes composing every nerve of any magnitude, and after •25


386 THE SOLIDS.

wards either passing into and mingling with those of a neighbouring nerve, or else returning back to that from which originally it started. It is now, however, very certain that some at least of the nerve tubes have a real termination : this is indisputably the case with the single filaments which enter the Pacinian bodies; it has also been shown to occur with many of the primitive tubes distributed to muscles.

PACINIAN BODIES.*

The Pacinian bodies are found in considerable numbers attached to the cutaneous nerves of the hands and feet, especially to those of the extremities of the fingers and toes ; they are also met with, though more sparingly, on other spinal nerves, on the plexuses of the sympathetic, but never on the nerves of motion, and in the mesentery ; in that of the human subject, however, they are only with great difficulty to be discovered, owing to its thickness, and the quantity of fat usually contained in it : in the mesentery of the smaller mammalia, as the cat, rabbit, &c, and more particularly when these are in a lean state, they may be readily discerned with the naked eye, and the entire of their structure followed out without even the employment of a reagent: it is, therefore, in these animals that they are studied to most advantage.

The Pacinian bodies vary greatly in size, but are usually as large as the head of a pin of ordinary magnitude; they are of an oval or pyriform shape, are perfectly translucent, attached to the nerve filaments by short pedicles, and occur either singly or sometimes in pairs. (See Plate XL VI. fig. 1.)

So large are these peculiar bodies, that the whole of their structure may be followed out with object glasses of an inch and half-inch foci; when examined with these magnifying powers, each Pacinian body is observed to consist of numerous concentric lamellae or capsules disposed with much regu