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=THE ANATOMICAL RECORD=
 
=THE ANATOMICAL RECORD=
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EDITORIAL BOARD
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Irying Habdbbtt
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Tulane UnlYontty
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Clabbncb M. Jackson
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Unlvenlty of MlMourl
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HOEACB JaTNB
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The Wtotar InstHute
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Thouas Q. Lbs
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UnlYWilty of Mlnnetota
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Fbbdbbic T. Lswis
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Harvard Unlventty
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Wabrbn H. Lbwis
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Johns Hopkins Unlventty
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Charlbb F. W. McClubx
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Princeton UnlTMitty
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William S. Millbb
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UnlTsnIty of Wisoonsin
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Flobbmcb R. Sabin
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Johns Hopkins Unlvanlty
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Gborgb L. Stbbbtbb
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Unlyerstty of Miohican
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G. Cabl Hitbbb, Managing Editor
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1880 Hill Street, Ann Arbor, Miohlfan
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VOLUME 4 1910
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PHILADELPHIA THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY
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PRINTED BT THE
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WILLIAMS dc WILKINB COIfPANT
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AT THE WAVBRLT PRMB
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BAIVnMOSE, IID.
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CONTENTS
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1910
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No. 1. JANUARY
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PAGC.
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CiEORGE S. Huntington. The phylogenetic relations of the lymphatic and bloodvascular systems in vertebrates 1
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William Snow Miller. Pancreatic bladders. With three figures 15
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W. M. Baldwin. An adult human pancreas showing an embryological condition. With one text figure 21
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Caroline McGill. The early histogenesis of striated muscle in the ojsophagus of the pig and the dogfish 23
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BOOK review A text-book of anatomy. Edited by D. J. Cunningham. By Henry W. Stiles. . . 49
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No. 2. FEBRUARY
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G. H. Parker. The phylogenetic origin of the nervous system 51
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C. JuDSON Herrick. The relations of the central and peripheral nervous systems
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in phylogeny. With one text figure 59
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Francis L. Land acre. The origin of the sensory components of the cranial ganglia.
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With three text figures 71
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John B. Johnston. The problem of the correlation mechanisms. With one text
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figure 81
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Proceedings of the American Association of Anatomists, Twenty-fifth Session.
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Boston, Mass., December 28, 29 and 30, 1909 93
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No. 3. MARCH
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James B. Murphy. Note on the sulcus lunatus in negro and white brains and its relation to the area striata. With sixteen text figures 115
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Nathaniel Alcock. The histology of the nasal mucous membrane of the pig. With fifteen text figures 123
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C. M. Jackson. A simple electric heater and thermo-regulator for paraffin ovens, incubators, etc. With one text figure 129
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(iii)
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IV CONTENTS
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No. 4. APRIL
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PAOB
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J. B. Johnston. The evolution of the cerebral cortex. With twenty figures 143
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Jacob Parsons Schaeffeb. On the genesis of air cells in the conchse nasales. With seven figures 167
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No. 5. MAY
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Wabben H. Lewis. The relation of the myotomes to the ventrolateral musculature and to the anterior limbs in amblystoma. With eight figures 183
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Wabben H. Lewis. Localization and regeneration in the neural plate of amphibian embryos. With eleven figures 191
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E. T. Bell. The staining of fats in epitheliimi and muscle fibers 199
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No. 6. JUNE.
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Helen Dean King. The effects of various fixatives on the brain of the albino rat, with an account of a method of preparing this material for a study of the cells in the cortex. With fifteen figures 213
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No. 7. JULY
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Jessie L. King. The cortico-spinal tract of the rat. With ten figures 245
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R. W. Habvet. a demonstration model of the brain-stem. With two figures 25^
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John L. Bbebieb. Notes on staining methods 263
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J. GoBDON Wilson. Intra vitam staining with methylene blue 267
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BOOK BEVIEW
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Fbanklin p. Mall. "Medical Education in the United States and Canada," Abraham Flexner 278
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No. 8. AUGUST
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Shinkishi Hatai. DeForest's formula for an unsymmetrical probability curve.. . . 281 RoLLo E. McCoTTEB. On the occurrence of pulmonary arteries arising from the
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thoracic aorta. With one figure 291
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Wesley M. Baldwin. A specimen of annular pancreas. With two figures 299
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Chables R. Babdeen. Practical state board examinations in anatomy 305
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BOOK bevibws
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J. Gobdon Wilson. Quain's elements of anatomy. E. A. Schafer and J. Symington 309
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A. G. Pohlman. Three recent text-books on topographical anatomy 311
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CONTENTS V
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No. 9. SEPTEMBER
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PAOK
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Franz Weidbnbbich. Die Morphologie der Blutzellen und ihre Beziehungen zu
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einander. Strassburg, Genn&ny. Neunundsechzig Figuren 317
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H. E. JoBDON. A further study of the human umbilical vesicle. Four figures. 341
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No. 10. OCTOBER
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Franklin P. Mall. A list of normal human embryos which have been cut into
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serial sections 355
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Richard W. Harvet. A cast of the ventricles of the human brain. Two figures 369
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R. R. Benblet. The cardiac glands of the mammalian stomach 375
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Arthur W. Meter. The question of applied anatomy 391
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No. 11. NOVEMBER
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Geo. S. Huntington. The genetic principles of the development of the systemic lymphatic vessels in the mammalian embryo 399
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No. 12. DECEMBER
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Alfred Jerome Brown. A note on post-cardinal omphalomesenteric communications in the adult mammal. Three figures 425
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Robert Ogden Moodt. Some features of the histogenesis of the thyreoid gland in the pig. Fourteen figures 429
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Edwin E. Reinkb. Note on the presence of the fifth aortic arch in a 6 mm. pig embryo 453
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H. R. Waht.. a simple dissecting table. One figure 460
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Robert Retzer. A criticism of our modem text-book of anatomy 461
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BOOK REVIEW
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Franklin P. Mall. Die neue Anatomische Anstalt in Munchen. Two figures.. 464
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THE PHYIX)GENETIC RELATIONS OF THE LYMPHATIC AND BLOOD VASCULAR SYSTEMS IN VERTEBRATES
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GEO. S. HUNTINGTON From the Anatomical Laboratory of Columbia University
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At a time when the ontogenesis of the vertebrate, and especially of the mammalian, lymphatic system has called forth general interest and considerable activity in research, it seems advisable to regard the mutual relations of the haemal and lymphatic divisions of the vertebrate vascular system from the standpoint of their phylogeny, in as far as material for such observations is to date available, and in turn to fit the facts ascertained by the study of manmialian lymphatic ontogenesis into the framework obtained by these generalized comparisons.
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This appears all the more advisable when we consider that any valid theory of lymphatic development must, on the one hand, agree in its postulates with the phylogenetic facts, as far as they are definitely established, and that, on the other hand, a review of the ascertained comparative conditions of the two systems in their mutual bearing on the general question will serve to direct attention to the problems of vascular morphology as yet imperfectly known, and thus guide the inquiries in the right direction.
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In the earliest zoological conditions in multicellular organisms a simple circulation suflSces to supply all the metabolic demands of the tissues. Such a circulation is attained when a sjrstem of intercellular canals develops in which a clear plasmatic fluid, without free cellular elements moves in response to the pulsations of contractile areas included within the system.
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In generd terms a circulation of this kind is, from the phylogenetic standpoint, a primary formation and represents the primitive lymphatic type of vascular organization, from which in higher forms the haemal system develops as a secondary vascular acquisition. In the physiological sense this establishment of a haemal circulation, as a graft on the earlier circulation of noncellular plasma, is to be interpreted as the expression of the increased rate of tissue combustion and the resulting growing demands of the organism for oxygen, required in the ascent to higher animal types. The biochemical agent which makes this elevation from the lower to the next higher rung of the zoological ladder possible, is the haemoglobin, and the morphological expression of its employment is found in the genesis of the modified mesodermal cell entering the circulation as the free red blood cell.
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The first circulation of this type contains in the plasma-stream cells which enable the organism to establish a very simple type of respiration. Such a condition in its earliest inception is represented by the circulatory apparatus of Amphioxus. With the elevation to more advanced vertebrate organization this mixed lymphatico-haemal type of circulation no longer suffices for the growing respiratory requirements, and, in response to the resulting functional demand, a separation of the original single circulatory system into two divisions begins to develop. One of these divisions continues on the hereditary lines as the rudiment of the future lymphatic system in the narrower sense, with cell free' plasma, while the other, arising primarily in response to the ever increasing demand of the tissues for oxygen, differentiates as the anlage of a haemal circulation with the haemoglobin cell as its distinctive biochemical and morphological character.
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In this process the bloodvascular system has gradually and continuously assumed more and more complex relations to the organism and has taken on successively higher and higher biochemical activities in addition to the original function of serving in the respiratory exchange, until it has morphologically and physiologically become the predominant vascular structure. The separation from the lymphatic channels has in consequence become more and more pronounced, until it has progressed in mammals to the point where, as the final outcome of the process, two distinct sets of vessels are established side by side. The component channels of one set, further specialized as arteries,
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PHYLOGENESIS OF VERTEBRATE VASCULAR SYSTEMS 3
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veins, blood capillaries and heart, are closely associated and mutuaUy interdependent, and give structural expression to the importance attained in the course of phylogenetic evolution by the haemal vascular system. The second set, that of the lymphatic channels, is in its main extent independent of the first, simpler and more primitive in its organization, and more restricted in function, closely interlocked with the venous division of the bloodvascular sjrstem which it in certain functional respects supplements.
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This division must of course have occurred gradually, and rather by multiplication of channels than by septal division of a single preexisting system into two components. Naturally this process should offer in the phylogenetic series many stages in which the division is still incomplete, and hence the gradual solution of peripheral organic continuity between hsemal and lymphatic vascular organization, in proceeding from the lower to the higher types, is, even with our present scanty knowledge, quite evident in the vertebrate series. No recent contributions to comparative vatecular anatomy have done more to clear this question and to advance our correct perspective than the investigations of Favaro^ on vascular organization in fishes.
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The Italian anatomist has described a very close and intimate relationship in teleosts between lymphatic and venous organization. In several forms the same vessels appear to function at certain periods as lymphatic channels, while at others they are physiologically venous in character. Hand in hand with this interchangeable functional relationship goes a marked complexity of the lymphatic and venous hearts.
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The investigations of Allen^ have led to similar results.
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In ascending the zoological scale we encounter, together with the increasing independence of haemal and lymphatic vascular
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Favaro, Guiseppe, 1905: II cuore ed i seni caudali dei Teleostei Ahi R, 1.
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Veneto di sc. lettr et arti, 1905-06, tome 65- Part II. Append, alia Dispensa, bet. 1906, Venejin 1906- Anat. Ana. Bd. 27, p. 879-880. Archivio di Fisiologia, Bd. 2, l-asc. 5.
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^ Allen, W. F.: Distribution of the Subcutaneous Vessels in the Head Region of the Ganoids, Polydon and Lepisosteus. Washington Acad. Sc. Proc., vol. ix, pp. 79-188, 1907. Distribution of the Subcutaneous Vessels in the Tail Region of Lepisosteus. Am. Jour. Anatomy, vol. viii, pp. 50-89, 1908.
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4 GEO. S. HUNTINGTON
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organization, a progressive and phylogenetically most significant reduction in the number, complexity and histiological differentiation of the lymph hearts. Favaro's demonstration of the primitive relationship between the teleostean lymphatic and venous system now completes the chain between the conditions presented by Amphioxus and those encountered next above the fishes in the urodele amphibians. This ascent is marked by a more definite separation of venous and lymphatic pathways, although the still large number (14-20) of the iu*odele veno-lymphatic hearts recalls the former more intimate association of the two systems.
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A reduction of the lymph hearts to two pairs, an anterior and a posterior, is next encountered in the aniu*e amphibians. In the reptiles only a single (posterior) pair of these organs is carried into the adult organization. The anterior lymph heart appears, however, during the ontogenesis in a rudimentary form, as determined by recent examinations of the 7.5 nun. and 9 mm. embryo of Scleroporus undulatus.
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In birds the posterior lymph heart is retained throughout life in some forms. In others, as shown by Sala,' it develops in the embryo, but disappears soon after the assumption of free life. While the subject is still under investigation, there is reason to believe that the presence of a rudimentary anterior lymph heart in birds during the ontogenesis can be demonstrated, and that this structure effects the final lymphatico-venous connection.
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In mammals, finaUy, a reduced single pair of anterior organs, the jugular lymph sacs, alone persists, as far as we at present know, as the sole remnants of the extensive antecedent series of lymphatico-venous connections and serves as the bond between the otherwise completely separated venous and l3anphatic systems.
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Thus the more prominent and highly specialized the hsemal vascular system appears as compared with the lymphatic, the higher in general is the animal organization possessing this type. Conversely, in descending the zoological series, the individuality and independence of the two systems diminishes steadily until they finally merge into the single conmion archaeal anlage.
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'Sala, L.: SuUo sviluppo dei cuori linfatici e dei dotti torarcici nell' embrione di poUo. Roma, 1900.
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PHYLOGENESIS OF VERTEBRATE VASCULAR SYSTEMS 5
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As previously stated* the lymph hearts represent in this evolutionary process, on the one hand, the line along which the gradually acquired organic separation of the blood-vascular and lymphatic systems proceeds, while on the other hand, they play in the various phases of this process of segmentation the important role of links between the lymphatic and the hsemal channels, which, in ascending the scale, are becoming progressively and incre^ngly more independent of each other.
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For obvious physiological and mechanical reasons this original connection can never be entirely interrupted, but we see in the relative organization of the lymphatic and venous systems in the mammalia, in comparison with the conditions formed in lower vertebrates, the highest degrees of this phylogenetically acquired independence.
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I have in a previous publication* pointed out the fact that the possibility exists in the plan of manmialian lymphatic organization for the establishment of lymphatico-venous connections at other points in the adult than those afforded by the typical connections of the anterior lymph heart or jugular lymph sac with the veins at the common jugular and jugulo^subclavian angles. Such connections, if they exist in certain forms, must be interpreted with our present knowledge of mammalian lymphatic organization, as retentions of other primitive lymph heart bonds between the lymphatic and venous system which, in the greater number of mammalia, are not developed and carried into the tjT)ical adult plan, but which may, while atypical for the general class, appear in certain specialized forms.
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It is quite conceivable that development on these lines would lead to results which would serve the mammalian physiological demands equally well, if not better, than the prevalent type of manunalian lymphatic organization. It is possible that the reported instances of the termination of the thoracic duct in one of the azygos veins or its tributaries in the adult human subject can be interpreted as variations depending for their genesis on the
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Huntington: The Genetic Interpretation of the Development of the Mammalian
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Lymphatic System. Anatomical R«5ord, vol. ii, nos. 1 and 2, 1908, pp. 1-44. » Loc. dt., p. 30.
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6 GEO. S. HUNTINGTON
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atypical development and retention of a lymphatico-venous heart formation at points other than the ones normally concerned in the production of the jugular lymph sac. The reported cases are, however, not sufficiently authentic to accept them at their apparent face value, and the available evidence is too scanty to warrant the assumption that these variations, if they exist, are of a progressive character tending toward the eventual reduction of the thoracic duct and the substitution for the same of a paore direct connection of the abdominal lymphatic channels with the venous system.
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The more our knowledge of comparative vascular anatomy grows, the clearer the perception becomes, that in spite of the apparent structural and functional differences between venous and lymphatic organization, the two systems are but parts of an originally single and united whole, and hence must be primarily of equal and identical origin. The genetic unity of all vascular structure is a proposition which is constantly becoming more self-evident. Even if it were not for the direct observations to the contrary, this fact alone negatives the assumption of the derivation of the systemic lymphatics from the veins as secondary products of their endotheUel proliferation. The line of reasoning above outlined, if carried to its logical conclusion, stamps the entire complicated haemal vascular apparatus of the higher vertebrate types as the genetic descendant of a preexisting simple lymphatic vascular system. In other words, in place of considering our modem Ijinphatics as derivatives from the veins, I believe that in a correct valuation of the relative position of veins and lymphatics, we are obliged to regard the lymphatic system as the primary organization, from which gradually in the phylogenesis the bloodvascular system has been derived. In spite of the predominance of haemal over lymphatic structure in the higher forms, the latter should be recognized as the phylogenetically older primarj'^ structure.
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The separation between the two has in the evolutionary sense become more and more pronounced, until it has progressed in the mammal to the point where, even in the ontogenesis, the anlages of both are laid down independently. But their common genetic
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PHYLOGENESIS OF VERTEBRATE VASCULAR SYSTEBiS 7
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basis is to be found in the vascular strands of the early mesoderm. It is however not at all improbable that the mammalian lymphatic system, as we at present know it, in the relatively few forms that have been carefully studied, is still in the evolutionary sense undergoing progressive changes which in their broader significance trend toward further reduction and simplification of the lymphatic, as compared with the haemal vascular organization. In view of the predominant association of the mammalian lymphatic channels with intestinal alimentation and the metabolic processes of digestion, such further evolutionary modification of lymphatic organization from the type now prevalent in mammalia, would in aU probability be in the direction of still greater development oi this physiological character. This might find structiu'al expression in the higher development of the intestinal lymphatic complex and a coincident reduction of the general lymphatic channels at present associated with them. The mammalian lymphatic system would under these conditions correspond mainly to the hepatic-portal venous channels and would convey the products of digestion directly to the systemic venous current.
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The organic principle of the above described phylogenetic separation of a haemal from a preexisting single primitive lymphatic circulation repeats itself within the far narrower circle of the former in the phylogenetic division which leads, through the Dipnoean and Perennibranchiate lines, to the replacement of the primitive single branchial type of respiration and circulation by the double cycle of the air breathing forms. This change in environment, with its resulting enlarged scope of vertebrate life, has led step by step to more highly organized structural types within the framework of the primitive haemal vascular system, through which stages the single-hearted, coldblooded branchial form has advanced to the double-hearted, warm-blooded pulmonary type.
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In its physiological significance this general evolutionary process again means primarily vastly greater and more rapid tissue metabolism or combustion in the broad sense. The structural response to this functional demand is strikingly given in the phylogenetic (and ontogenetic) development of the intra-cardiac and intra-aortic septa. We encounter here on a large and unmistakable scale, and associated with an evident biochemical function, the division of part of the originally simple and imifonn hsemal vascular system of cardiac chambers and truncus arteriosus into two bilateral and equivalent elements. This change is effected primarily not by addition from wiOwvt (except the neomorphism of the pulmonary vein) of something new but by a change and re^arrangement of parts already existing within the framework of the primary bloodvascular system. If, therefore, as McClure and I have definitely proved,* the manmialian jugular lymph sac, or cervical lymph heart, is secondarily separated from the manunalian embryonic pre- and postcardinal veins, this process of division of originally single hsemal channels into completely separate elements is not genetically a new process, confined to the lymphatico-venous terminal, but follows on a smaller scale and much more obscurely, genetic lines already laid down in the division of the primitive single heart tube into its completely distinct dextral and sinistral components.
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The question here involved is of great and far reaching importance in establishing the correct relative position and value of the hsemal and lymphatic vascular systems.
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If the metabolic demand for increased and more rapid supply of oxygen is capable of calling into existence, within the already organized confines of the hsemal division of a simple vertebrate circulation, the structiu*al changes leading to the divided heart and the lung in place of the antecedent branchial type of circulation and respiration, then the same force is evidently suflScient to derive, in far earlier phylogenetic stages, from the primitive general non-cellular circulatory system, a separate set of channels conveying plasma with free haemoglobin cells as the circulating medium, and developed primarily in the service of the oxygen-carbon dioxide exchange of the tissues.
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In this way there comes to be established the phylogenetic
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• Huntington and McClure: The Anatomy and Development of the Jugular Lymph Sacs in the Domestic Cat. Anatomical Record, vol. ii, nos. 1-2, 1908, pp. 1-18.
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PHYLOGENESIS OF VERTEBRATE VASCULAR SYSTEMS 9
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anlage of a secondary bloodvascular system, derived from the primitive general vascular apparatus circulating non-cellular plasma. With the appearance of the hsemd system the dis* tinction between it and the persistent portion of the primitive vascular organization as a lymphatic system develops.
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Thus the primitive simple hsemal system, subsequently destined to xmdergo imder the stimulus of phylogenetic advance, a complete secondary division, was in its own turn originally segmented from a simpler antecedent circulation of lymphatic type for the pmpose of satisfying the earliest demand of the tissues for oxygen by becoming the carrier of hsemoglobin cells, while the persistent elements of the earUer system are retained as lymphatic vessels serving a new physiological purpose under changed conditions of metabolism.
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As stated above the series of lymph hearts would in this genesis of the bloodvascular system represent points where the original continuity of lymphatic and haemal elements is retained, in a specialized and modified form for definite physiological purposes. The number and distinctive character of these lymph hearts would then naturally diminish in proceeding seriaUy from the lowest to the highest types, coincident with the serially developed greater and greater independence of the hsemal and lymphatic divisions of a general vascular system.
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This change impUes an enormous degree of adaptability and structural response to fimctional demands. Many examples of this extreme plasticity of vascular organization are encountered throughout the entire formative period of the manmiaUan embryo, in which the bloodvascular system is the predominant agency of nutrition as well as respiration. This character appears not only in the crystallization of definite assymetrical arterial and venous pathways from an antecedent symetrical bilateral type, but also in many of the more intricate relations of the bloodvascular channels to the temporary and the future permanent metabolic demands of the tissues. Thus, for instance, in the placentalia the vitelhne veins appear in the r6le of the earliest embryonic nutritive and respiratory channels. They subsequently, in the placentd period, yield this part to the secondarily involved um
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10 GEO. S. HUNTINGTON
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bilicals. Their own primary signifiance is lost and remains in abeyance throughout the whole of the placental epoch, to suddenly reassert itself when the hepatic portal channels, as the direct descendants of the afferent vitelline veins, assume with, the establishment of intestinal aUmentation at birth, the important share in the nutritive processes of the body which they are henceforth to maintain throughout the life of the individual. The anlages of these vessels were, so to speak, side-tracked for the very considerable umbilical or placental period of embryonic and foetal existence. But they continued to develop dm^ing this entire period of functional displacement and obscurity, and became associated with the growing alimentary canal, in anticipation of the moment when, with the first establishment of post-foetal conditions, they resumed their original significance and entered into their now definite and permanent function as nutrient afferent hepatic vessels.
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In the same way the entire extensive series of structural changes within the three divisions of the bloodvascular system, leading finally to the establishment of the pulmonary circulation, is developed in anticipation of the sudden assumption of pulmonary respiration at birth.
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This law of anticipatory ontogenesis is of very wide application and expresses especially the cardinal character of extreme adaptability, both to present requirements and future needs of the organism, in all developing vascular structure.
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It is quite possible, that the lymphatic vessels, which we must recognize in the broad phylogenetic ground plan of vascular organization, as the primary and earliest channels, appear in the complicated and highly specialized manmiaUan vascular system of predominantly haemal type, in a subordinate and secondary position, owing to genetic influences of this general character.
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They are formed, during the embryonic period, just as the portal and pulmonary channels are formed, but like these, they develop in anticipation of assuming their functional activity only with the altered environment and changed nutritive conditions of the post-foetal period.
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In this sense they appear as secondary structures, allied to the
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PHYLOGENESIS OF VERTEBRATE VASCULAR SYSTEMS 11
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all important hsemal embryonic channels, just as the placental viteUine veins, within narrower phylogenetic limits, appear subordinate to the new bloodvascular conditions dependent upon the acquisition of the umbilical vein as the main embryonic nutritive and respiratory vessel, in the phylogenetic ascent from the vitelUne to the placental phase of embryonic development.
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This brings us to the question of the comparison between the ontogenesis of the mammaliam systemic lymphatics and the lymphatic organization of the lower vertebrates. Briefly stated, our observation as to the development of the mammalian lymphatic vessels, can be summed up as follows:
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1. The first anlages of the bloodvascular channels and of the systemic lymphatic vessels in the mammalian embryo are identical. These common anlages are formed by independent intercellular mesodermal tissue spaces, which, in enlarging, become Uned, in obedience to the mechanical pressure effects of the clear fluid contents of the spaces, with endothelium.
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2. The spaces become confluent to form larger and continuous channels. The bloodvascular system differentiates genetically from the lymphatic system by the secondary inclusion of the speciaUzed mesodermal haemoglobin cell of the blood islands in the clear non-cellular stream of the plasma circulating during the primary stage in the hsemal system of channels in response to the cardiac pulsations.
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The systemic lymphatic channels continue on the other hand, to convey a clear fluid containing no, or only a few, cellular elements.
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3. This histogenetic identity, and the fact that subsequently the only criterion defining respectively the early embryonic bloodvascular and lymphatic channels is the red blood ceU content of the former, precludes definite differentiation of the two sets of vessels prior to the period at which the haemal channels acquire their distinctive free cellular elements.
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4. Hence we must accept three chronological possibilities in regard to the ontogenetic period at which these anlages begin to appear. :
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a. The bloodvascular and lymphatic channels develop siniul
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12 GEO. S. HUNTINGTON
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taneously as capillary anlages side by side, and subsequently differentiate firom each other as above detailed.
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b. The lymphatic anlages are the first to develop. Subsequently a portion of the conunon system, or a second generation of equivalent channels, differentiates as the hsemal component of the vascular system, in contradistinction to the persisting primary lymphatic system.
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c. The bloodvascular system is ontogenetically the first to develop in the mammalian embryo. The lymphatic anlages appear secondarily as an equivalent system of mesodermal spaces, which subsequently unite. The resulting channel system does not acquire the free circulating blood cells characteristic of the hfiemal division, but finally gains access to the blood vascular system by union with the jugular lymph sacs, derived from the veins, and is thus enabled to enter as an integral component into the triple constitution of the general circulatory apparatus.
 +
 +
From the phylogenetic standpoint the second of the above enumerated possibilities is the one which is most consistent with the haemo-lymphatic organization as seen in its general evolution in the vertebrate series. At the same time the last of the three possibilities appears from the evidence at hand to represent most acciu'ately the conditions encountered in mammalian embryos. The separation between bloodvascular and systemic lymphatic organizations has here not only progressed to a degree in which even the ontogenetic anlages of the two channel systems are laid down independently of each other, but has further resulted in placing their first appearance into different embryonic periods.
 +
 +
From the phylogenetic standpoint this must be regarded as the result of factors operative in the speciaUzation of the highest vertebrate types, and not as the original common condition. The mammalian ontogenetic relationship between the haemal and lymphatic anlages appears as an expression of the tremendous development which in the evolution of the higher zoological types, the bloodvascular system has gained over the primary lymphatic circulation. This paramount influence of haemal over lymphatic vascular development has even reversed the relative ontogenetic period in which the first distinct anlages of
 +
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PHYLOGENESIS OP VERTEBRATE VASCULAR SYSTEMS 13
 +
 +
each system appear. The bloodvascular organization has gained the complete ascendancy, the lymphatic has been relegated to a secondary position, with highly curtailed and specialized function. Moreover, as above stated, the actual assumption of this function has been in the mammalian ontogenesis postponed to the end of the placental epoch, and the assumption of individual nutrition with the eatabUshment of the definite postnatal conditions.
 +
 +
Compared with the position of the lymphatic circulation in the ancestral series, one is almost tempted to characterize its development in the placental embryo as the reversional appearance of a system, formerly of much greater extent and importance, but now to a large extent replaced by more modem zoologies^ acquisitions, and retained only in a modified and reduced form with greatly restricted functional application.
 +
 +
At any rate, there is no radical inconsistency in the observed facts, either of the phylogenetic or ontogenetic history of vertebrate lymphatic vessels.
 +
 +
In respect to their genesis in the mammalian embryo, it makes but Uttle difference as to exact embryonic period in which they make their first appearance as definite lymphatic anlages.
 +
 +
Their development may be synchronous with that of the earliest haemal channels, or precede these, or finally, as seems to be actually the case, they may first appear distinctly after the main embryonic bloodvascular lines have been laid down.
 +
 +
Their ultimate secondary union with each other, and then with the venous system through the intervention of the comphcated jugular lymph sacs, and the entire character of the completed adult lymphatic-system as a ^* shadow-picture" of the venous organization, suggests strongly that the macMnalian lymphatic vessels have phylogenetically acquired this secondary position relative to the dominant haemal vascular system.
 +
 +
This subordination of lymphatic to bloodvascular structures manifests itself not only in the morphological relations existing ontogenetically and in the adult between the two systems, but the same influence has operated to retard the embryonic appearance of the first definite lymphatic anlagen to a period in which the
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 +
 +
14 GEO. S. HUNTINGTON
 +
 +
blood-vascular organization has already assumed clear cut and definite character.
 +
 +
We thus reach the end-link in the long chain of successive diflferentiations which lead through the vertebrate series to the final stage in which the greatest attainable degree of independence between lymphatic and haemal vascular structiu*e has been reached, and in which the primitive relative value to the organism of the two systems has been reversed, in obedience to the law which has stamped the bloodvascular system as the main organic line of evolutionary progress.
 +
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Googk
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PANCREATIC BLADDERS
 +
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WILLIAM SNOW MILLER Fmm the Anatomical Laboratory of the University of Wisconsin
 +
 +
For several years I have not given the course in mammalian anatomy which forms part of the work introductory to the study of human anatomy, at the University of Wisconsin, louring the summer session of the present year (1909) it fell again to my lot to give this course, and one of the animals used presented a variation not unusual in our laboratory, a pancreatic bladder.
 +
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In two earher communications I have called attention to the occurrence in the domestic cat of a pancreatic bladder which bears a similar relation to the pancreatic ducts that the gall bladder does to the bile ducts.
 +
 +
With the description of the present case there are now on record seven cases in which this peculiarity was present and of the seven cases, five have been found in the anatomical laboratory of the University of Wisconsin. The first case was described by Mayer in 1815, a second by Gage in 1879, three cases by myself in 1904 and a fourth case in 1905.
 +
 +
That five of the seven cases should be found in a small community seems to indicate, either that there exists locally a special breed of cats, or that there has been a lack of careful observation on the part of those instructors whose courses include the dissection of the cat.
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 +
It is not improbable, however, that some cases of a pancreatic bladder have been overlooked, having been mistaken for cases in which a double gall bladder was present.
 +
 +
It is my custom when students take up the study of the viscera of the cat, to inject with a different colored starch mass the bile ducts and the pancreatic ducts. This is easily done by making an opening in the duodenum 25 to 30 mm. in length opposite the
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16 WILLIAM SNOW MILLER
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entrance of the ductus choledochus, thus exposing the oval opening leading into the ampulla of Vater. With but little diflSculty a cannula can be inserted and tied in the ductus choledochus and the injection of the bile ducts and gall bladder completed. It often requires some skill and patience to introduce a second cannula by the side of the first into the ductus pancreaticus; but the technique once acquired, rarely does anj'^ diflSculty present itself.
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By this simple procedure the student is able to follow the gross distribution of the bile and pancreatic ducts and, as I usually inject the arterial system, the systemic veins and the portal system witli still diflferent colored masses, the relation which these ducts bear to the blood vascular system is easily made out.
 +
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The case I now record was found in a young male cat obtained from a part of the city far removed from that of the preceding cases; therefore it seems quite improbable that this cat was in any way related to the others.
 +
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The type is that of the second and third cases that I have desscribed, namely, a duct leading from the duodorsal division of the ductus pancreaticus and terminating in a well-defined bladder situated a httle to one side of and dorsal to the gall bladder, which occupies its usual position in the right median lobe of the liver. It dififers from the other cases in that there is a triangular flap of pancreatic tissue surrounding the entrance of this duct into the duodorsal division of the ductus pancreaticus. Because of this peculiarity the present case occupies a position between the second case described by Heuer (see below) and the cases previously described by myself. The relations of the various parts are shown in fig. 1.
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The question as to the origin of these pancreatic bladders at once presents itself, and in this connection it is interesting to note two variations of the pancreas found by Heuer while studying the arrangement of the pancreatic ducts of the cat.
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 +
In the first case (fig. 2) a band of glandular tissue, an outgrowth from the caput, passed cephalad, following the ductus choledochus and cystic duct and partially covering them on their ventral side. It extended to
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PANCREATIC BLADDERS 17
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about the middle of the gall bladder, where it fused with the connective tissue around the latter. It had a duct which passed down its entire length and joined the axial branch of the caput. In the second case (fig. 3) a similar though slightly narrower band of glandular tissue extended from the caput alongside of the ductus choledochus and ductus cysticus. It then continued along the left side of the gall bladder to the posterior (ventral?) part of the liver, where it enlarged into an oval
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Fig. 1. Drawn in situ. Shows the relation of the pancreas and the pancreatic bladder to the liver, stomach and duodenum. The liver has been turned cephalad; the stomach is in outline.
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 +
G. B., gall bladder; R. L., right lateral lobe of the liver; L. L., left lateral lobe of the liver; P. B., pancreatic bladder; P., pancreas; D., duodenimi.
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 +
The triangular flap of pancreatic tissue mentioned in the text can be seen extending from the pancreas along the duct connected with the pancreatic bladder. One-half the natural size.
 +
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nodule about one centimeter in its long diameter. This nodule occupied a hollow in the right central lobe of the liver to the left of the gall bladder. A duct was present which extended from the nodule down the middle of the band, and joined the axial branch of ihf caput as in the previous case.
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The pancreas is usually described as arising from a dorsal and a ventral anlage which fuse after rotation of the duodenum has taken place, the ventral anlage giving rise to the ductus pan
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18
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WILLIAM SNOW MILLER
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creaticus (Wirsung) while the ductus accessorius (Santorini) takes its origin from the dorsal anlage.
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 +
In cyclostomes and selachians a dorsal anlage only is present, in all the remaining vertebrates a dorsal and ventral anlage is found and the investigations of Stohr, Goppert, Saint-Remy, Felix, Hammer, Stoss, Wlassow, and others have shown that the ventral anlage is paired, a pancreatic diverticulum arising on
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Fig. 2. Schematic drawing constructed from Heuer's description of his first case of a pancreas with three principal divisions.
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 +
D., duoaenum; G. B., gall baldder; R. L., right lateral lobe of the liver; L. L., left lateral lobe of the liver; P., pancreas with a band of pancreatic tissue extending along the ductus choledochus.
 +
 +
each side of the liver stalk. The left ventral outgrowth usually disappears, the right persisting and maintaining its association with the liver stalk which now becomes the ductus choledochus. Returning now to the cases of Heuer: it seems probable that in each case both the right and left ventral anlage persisted, the left in case one (fig. 2) giving rise to the broad band of pancreatic tissue extending along the ductus choledochus and ductus cysti
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PANCREATIC BLADDERS 19
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cus, while in the second case (fig. 3) the left anlage was drawn out into a long narrow band with an enlarged distal end. Now if we conceive the narrow band of pancreatic tissue in the second of these cases to undergo a degeneration leaving only the duct, and the distal enlarged portion converted into a dilatation, we have a complete series of changes through which these pancreatic bladders may have arisen.
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Fig. 3. Outline drawing of Heuer's second case of a pancreas with three principal divisions.
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D.. duodenum; G. B., ^all bladder; R. L., right lateral lobe of the liver; L. L., left lateral lobe of the liver; P., pancreas with a long narrow band of pancreatic tissue extending along the ductus choledochus and terminating in an expansion situated on the left side of the gall bladder. (After Heuer.)
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Another and more probable hypothesis may be advanced, namely: that the ventral anlage, in place of being double, may in these cases be bi-lobed, either from the beginning, or as a result of fusion, one of the lobes having given rise to the caput of the pancreas and the other to the bands of pancreatic tissues found by Heuer, or to the pancreatic bladders which I have found.
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20 WILLIAM SNOW MILLER
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That the ventral anlage is in some cases bi-lobed, the investigations of Wlassow on the development of the pancreas of the pig have shown.
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I have described this additional case of a pancreatic bladder and suggested two possible explanations of the origin of these bladders in order that attention may again be called to the anomaly and to the embryological questions involved, and to stimulate more careful observation on the part of those who give courses in mammalian anatomy.
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LITERATURE
 +
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Fblix, Wai/teb. Zur Leber- und Pancreasentwicklung. Arch, f . Anat. u. Phys.
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1892. Anat. Abt.
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Qagb, S. H. The Ampulla of Vater and the Pancreatic Ducts of the Domestic Cat.
 +
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1879. Amer. Quart. Mic. Jour. vol. 1.
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GOppebt, Ernst. Die Entwickelung und das spfttere Verhalten des Pancreas der
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1891. Amphibien. Morphol. Jahrb. Bd. 17.
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1893. Die Entwicklung des Pancreas der Teliostien. Morphol. Jahrb.
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Bd.20. Hammab, J. Aug. Einige Plattenmodelle zur Beleuchtung der fOheren embrionalen
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1893. Leberentwicklung. Arch. f. Anat. u. Phys. Anat. Abt.
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Heueb, Q. J. The Pancreatic Ducts in the Cat. Johns Hopkins Hosp. Bull. vol.
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1906. 17.
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Mater, A. C. Blase fOr den Saft des Pancreas. Arch. f. Anat. u. Phys. Bd. 1
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1815. Miller, W. S. Three Cases of a Pancreatic Bladder Occurring in the Domestic Cat.
 +
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1904. Amer. Jour, of Anat., vol. 3.
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1905. A Pancreatic Bladder in the Domestic Cat. Anatom. Abe. Bd. 27. Saint-Rbmy, Q. Recherches sur le d^veloppment du pancreas chez les Reptiles.
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1893. Joum. de Panat. et de la physiol. Ann^e 29.
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St5hr, Ph. Die Entwicklung von Leber und Pancreas der Forelle. Anatom. Anz.
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1893. Bd. 8. Stoss. Zur Entwicklungsgeschichte des Pancreas. Anatom. Anz. Bd. 6.
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1891. Wlassow. Zur Entwicklung des Pancreas des Sohwein. Morphol. Arb. Bd. 4,
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1895.
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AN ADULT HUMAN PANCREAS SHOWING AN EMBRYOLOGICAL CONDITION
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W. M. BALDWIN Cornell University Medical College
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 +
This unusual pancreas was removed from the body of an adult white female, 71 years old, who had died of "valvular heart disease. The abdominal cavity presented a number of anomalous conditions, among these an abnormal duodenum and pancreas. The duodenum, which was of the V-shaped variety, presented an ascending limb lying to the right of and ventral to the descending limb.
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D. PANC ACC.
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OUOOENUM
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D. CHOL
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0. PANC.
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The pancreas, represented in the figure as seen from the dorsum, consisted of two parts luiited with each other by a narrow strand of glandular tissue dorsal to the duodenum. The larger por
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22 W. M. BALDWIN
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tion lay ventral to the bodies of the first and second lumbard vertebrae upon the left side of the descending limb of the duodenum.
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Because of the pecuUar V-shape of the duodenum this portion of the pancreas was not situated within the loop nor did it have any relation to the transverse or ascending portions of the duodenum. It lay dorsal to the stomach and extended a distance of only 5.0 cm. towards the left kidney possessing a cephalocaudal diameter of 3 cm. and a maximum thickness of 1.3cm. Traversing themiddle of the glandular sustance, a single large duct passed with increasing calibre from left to right finally emptjdng into the duodenum 4.0 cm. caudal to the pylorus.
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The other smaller portion of the gland lay dorsal to the duodenum and on a level slightly caudal to the part just described. Its long axis .extended along the conmion bile duct, which traversed it ventrally, a distance of 3.0 cm. with a width of 2.0 cm. and a maximum dorso-ventral dimension of 1.5 cm. Coursing through this tissue a single small duct passed caudally to empty finally upon the dorsal wall of the duodenum in company with the common bile duct. This duct approached the caudal aspect of the latter. The narrow band of pancreatic tissue which joined both portions of the gland was drained by radicles of both ducts, yet the ducts were not in communication with each other. Upon the duodenal mucosa, the openings of the ducts were separated by an interval of 3.5 cm., the duct from the larger portion being cephalic and ventral.
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This anomaly seems to be an instance of the non-fusion of the primitive ventral and dorsal pancreatic anlages, together with an insufficient "rotation" of the ventral anlage around the duodenum. The dorsal portion of the gland in close apposition to the common bile duct corresponds to the ventral anlage which forms ultimately the caudal portion of the head of the adult pancreas and the terminal portion of the main pancreatic duct. The larger portion, derived from the dorsal anlage, represents the remainder of the head and all of the neck and body of the gland together with the enclosed ducts.
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Received for publication, November 20, 1909,
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THE EARLY HISTOGENESIS OF STRIATED MUSCLE IN THE (ESOPHAGUS OF THE PIG AND THE DOGFISH
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CAROLINE McGILL
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Instructor in Anatomy, University of Missouri With Twenty-Five Figures
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Striated muscle is described by most investigators as coming exclusively from the inner plate of the myotome. In the later development of the tissue each muscle fiber is usually said to arise from a single myoblast. Neither of these statements holds good however, regarding the oesophagus of at least the two forms studied, as will appear from the following description of the early development. A brief review of the literature on this subject will first be given.
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LITERATURE REVIEW
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The literature, for convenience, is here divided into three classes: (1) the papers which describe the origin of striated muscle in general from the germ layers; (2) those which describe the transformation of the myoblasts into muscle fibers; and (3) those which describe the histology of the adult oesophageal muscle.
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(1) Vertebrate striated muscle, with the exception of one of the inner eye muscles of the chick, is almost universally described as arising from the mesoderm. Herzog ('02) found that in the chick the sphincter of the pupil develops from ectoderm. The mode of transformation of mesoderm into muscle-forming tissue (pre-muscle, as it is termed by Lewis '01) is disputed. The three early derivatives of the mesoderm, the myotome, the mesothelium and the mesenchyme, each have been considered bj'^ various writers to be the muscle-forming tissue. For a complete review of the literature on this subject the reader is referred to the paper by Maurer, Die Entwickelung des Muskelsystems und der elektrischen Organe, — ^in the Hertwig's Handbuch d. Entwickelungs
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24 CAROLINE MCGILL
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lehre der Wirbeltiere, Bd. 3, (1906). Remak ('55) and Balfour C85) believed that striated skeletal muscle is derived from both the outer and inner plates of the myotome. The Hertwigs ('81) in Selachians, Minot ('92) in the frog, Godlewski ('02) in the rabbit, mouse and guinea-pig, Dahlgren and Kepner ('08) in Catostomus, with many other investigators, found striated muscle arising exclusively from the inner plate of the myotome. The head muscles have usually been described as arising from the epithelium of the head somites (Marshall, '82, in Selachians), but Renter ('98) found that in the pig the outer eye muscles develop from the head mesenchyme.
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Lewis and Bardeen ('01) stated that in the human embryo '*The skeletal and muscular structures of the limbs are differentiated from the mesenchyme of the limb buds." Lewis ('01) discovered that in the arm of the human embryo the muscle develops directly from mesenchyme. He gives a good review of the literature on the origin of the limb muscles, to which the reader is referred. Since Lewis' paper appeared, Ingalls ('07) has described the origin of the limb muscles from the outer layer of the myotomes in a 4.9 mm. human embryo.
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Mlodowska ('08) studied the development of striated muscles in the chick, mouse, rabbit, and pig, and found that most of the skeletal muscle arises from muscle plates, but that the surrounding mesenchyme aids in the later formation.
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(2) There are two general theories advanced to account for the origin of the multinucleated striated muscle fiber from the undifferentiated muscle tissue. One is that each primitive myoblast develops into a single muscle fiber, the other is that several myoblasts fuse to form the muscle fiber. The latter is the syncytial theory of muscle origin. Remak ('50- '55), KoUiker ('51), Schultze ('61), Hertwig-Mark ('92), Minot ('92), Bardeen ('00), Eycleshymer ('04), Maurer ('06), and Dahlgren and Kepner ('08), adhere to the unicellular origin of the muscle fiber. Maj^o ('62), Calberla ('76), Marchesini, and Ferrari ('96), Godlewski ('02), Mlodowska ('09) and numerous other writers, claim that the muscle fiber is of syncytial origin. The syncytium, most of these investigators believe, is formed by a secondary fusion of
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HI8TOGEN8IS OF STRIATED MUSCLE 25
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independent epithelial myoblasts. Bom (73), Calberia ('76), Minot ('92), and Maurer ('06) give complete reviews of the literature, so a rfeum^ of the papers of earlier investigators is unnecessary.
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(3) The structure of the muscle of the adult oesophagus. Oppel ('97) gives a lengthy review of the Uterature on the structure of the muscle of the vertebrate oesophagus, to which the reader is referred. Since the structure of the adult muscle throws some light on the development, a short review of a few of the papers is given here. According to Oppel, all of the muscle of the oesophagus of amphibia, birds, and reptiles is smooth. In most fishes and mammals, a marked differentiation of smooth into cross-striated muscle has taken place. In some of the fishes both layers of muscle are striated throughout the length of the oesophagus; in other fishes only one layer, usually the thicker inner one is striated. Mammals also have varying amounts of striated muscle. In ornithorhynchus, all of the muscle in both layers is smooth, just as in amphibia, reptiles and birds. In a niunber of mammals (giraffe, elephant, all rodents, cattle and sheep) both layers of muscle are striated down to within onefourth inch from the cardia. In some manunals striated fibers of the outer or longitudinal layer have been described as extending for a distance upon the cardia. Between these two extremes are all transitions.
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Oppel states also that the primitive vertebrate probably possessed only smooth muscle in the oesophagus. The presence of striated muscle where it does occur, he thinks is due to a downgrowth of the muscle of the pharyngeal constrictors upon the oesophagus. He thus derives the striated oesophageal muscle from the branchial muscle \yhich is held by most investigators to arise from the lower head myotomes.
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Coakley ('92) describes striated muscle fibers in the upper part of the human oesophagus as having a structure precisely like that of the skeletal muscle. In the lower oesophagus he found scattered striated fibers in both layers extending as far as the stomach. These lower fibei's do not show as distinct crossstriations, as do the ordinary striated muscle fibers. He believes
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26 CAROLINE McGILL
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that they are an intermediate form between smooth and crossstriated muscle. Though not so stated, he evidently thinks that the striated muscle here is formed directly from the smooth muscle.
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Flint ('07) worked only on the grosser structure of the oesophagus of the pig embryo. The striated muscle is formed, he states, by differentiation of the mesenchyme. In the 13 nam. pig embryo the mesenchyme cells have begun to elongate. By the time the embryo is 7.5 cm. long, both layers of muscle are differentiated. The first evidence of cross-striation appears at 11 cm.
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The writer ('07) in a description of the development of smooth muscle in the oesophagus of the pig, found the striated muscle developing somewhat earlier than described by Flint. There is an elongation of mesenchyme cells to form the circular layer beginning in the mid-oesophagus of the 5 nam. pig. In the 8 mm. embryo the elongation of cells extends the entire length of the oesophagus. From this differentiated mesenchyme, in the upper and mid-oesophagus, striated muscle develops; in the lower oesophagus, smooth muscle.
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MATERIAL AND METHODS
 +
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The oesophagus of the dogfish (Acanthias vulgaris) and of the pig was the material used. Serial sections of dogfish embryos from 3 mm. to 60 mm. in length were studied. The embryos from 3 mm. to 10 mm. long were fixed in Zenker's fluid. All the longer ones were fixed in sublimate or in sublimate-acetic solutions. The pig embryos used ranged from 4 mm. to 60 mm. in length. Thej'^ were all fixed in Zenker's fluid and were cut in serial sections. All were embedded in paraffin. The sections were stained in Delafield's haematoxylin, Heidenhain's iron-hsematoxylin with a counter stain of Congo red, and in Mallory's aniUn blue connective tissue stain.
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OBSERVATIONS
 +
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This paper is restricted to the early development of striated muscle in the oesophagus. The later development, including the differentiation, growth, and multiplication of the fibers, is reserved for a separate paper.
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HISTOGENESIS OF STRIATED MUSCLE 27
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For tracing the origin of the myoblasts, dogfish embryos were used. The later transformation of myoblasts into muscle fibers was studied chiefly in pig embryos.
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(1) The Origin oi Myoblasts in the (Esophagus
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As already mentioned in the literature review, Oppel ('97) found the striated muscle of the oesophagus to be a downgrowth of pharyngeal muscles, hence arising indirectly from the myotomes of the branchial region. Flint ('07) and the writer ('07) state that it arises from the mesenchyme surrounding the endodennal tube.
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In both dogfish and pig embryos, the oesophageal striated muscle arises directly from the mesenchyme. There is apparently no downgrowth from the pharyngeal region, at least in the dogfish. To be sure of this it was necessary to study early embryos and to trace the development of the mesenchjine cells in which the muscle arises. This was done in the dogfish material.
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The earliest dogfish embryo studied by the writer was 3 mm. in length. At this stage there are very few mesenchyme cells formed. The mesoderm is represented by two layers, the somatic and splanchnic, which have extended dorsalward and form a number of myotomes. In places in the head region from the splanchnopleure at its jimction with the myotome, a few irregular cells seem to be arising, which may represent the first mesenchymal 'Cells. Minot ('92) stated that the mesenchyme arises solely from the mesothehum, the cells leaving the mesothelium, but remaining connected with it and with each other by protoplasmic processes. Thus from its origin the mesenchyme is a syncytium. He also found that the first mesenchyme of elasmobranchs arises from the splanchnic layer at the point where the myotome unites with the nephrotome.
 +
 +
Fig. 1. is a crossHBection through the upper oesophagus of a 3 mm. dogfish embryo. There is nowhere in this embryo any distinct mesenchyme formed. At a in fig. 1. is a stellate cell which seems to have formed from the mesothehum, and is still connected with it by protoplasmic bridges. It may be one of
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28 CAROLINE MCGILL
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the earliest mesenchyme cells. The mesotheUal cells at this time have numerous processes which extend to the surroimding organs. Fig. 4 is a high power drawing of area X in fig. 1, and shows these processes distinctly. They are most numerous dorsal and ventral to the coelom.
 +
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Fig. 2 is drawn from a section near the mid-oesophagus of the same 3 mm. embryo. The myotomes are shown connected with the coelomic mesotheUum by a narrow strand of irregular cells. Under high power (fig. 5) these cells are found to be connected by wide anastomoses, and from them numerous processes extend to the ectoderm and the endoderm. They have much the appearance of mesenchyme cells, but sections of a later embryo at this region show that no true mesenchyme has yet been formed.
 +
 +
Fig. 3 is through the lower oesophagus of the same embryo as shown in figs. 1 and 2. At this point the two layers of the mesothehum are distinct and the coelomic cavity extends into the myotome. Fig. 6 is a high power drawing of area X in fig. 3. There are wide protoplasmic anastomoses between the two layers of mesothelial cells, and many finer processes extend to the basement membranes of the ectoderm and the endoderm. In the 3 mm. embryo the myotome is in contact with the epithelium of the oesophagus, but a study of later stages shows that before the mesenchyme, which later surroimds the oesophagus, is formed, the myotomes have grown some distance dorsalward and are well removed from the oesophagus. At a later stage, also, most of the protoplasmic processes of the mesothelial cells have been withdrawn, so it is probable that they do not represent the anastomoses of the later mesenchymal syncytium.
 +
 +
Since syncytium, as used in recent anatomical writings, has had various meanings, its definition as here employed is given. By syncytium is meant any tissue where there are well defined protoplasmic anastomoses between the cells. Where all the cells are so united, the tissue is described as a complete syncytium. Where some of the cells are independent and others are connected, the term partial syncytium is used. By cell, as employed in describing a syncytium, is meant merely the irregular stellate or spindle shaped mass of protoplasm which makes up a nodal
 +
 +
 +
HISTOGEN8IS OF STRIATED MUSCLE 29
 +
 +
point of the protoplasmic network, together with the enclosed nucleus.
 +
 +
In the 4 mm. dogfish embryo the coelomic epithehum has grown far forward beyond the region of the oesophagus; and from it, around the brain and upper pharynx, considerable mesenchyme is forming by the outgrowth of stellate cells from the mesothelium. In the neighborhood of the oesophagus, the condition is almost precisely as in the 3 mm. dogfish, with the exception that the myotomes have grown farther dorsalward.
 +
 +
Fig. 7 is from the upper oesophagus of a 5.5 mm. dogfish embryo. Here the myotome is well formed and has grown well away from the endodermal tube. The mesothelium is distinctly epithelial and shows fewer cytoplasmic processes than were present in the 3 mm. embryo. Though no mesenchyme is yet present in this region, it is well formed as a complete syncytium filling in the spaces between the organs in the head region.
 +
 +
Fig. 8 is from the mid-oesophagus of the same embryo as shown in fig. 7. Here there are a few stellate cells between the splanchnic layer of the mesoderm and the endoderm, but the high power drawing (fig. 9) of area of X in fig. 8 shows that most of these loose cells are really endothehal cells. The blood vessels are growing in at this stage.
 +
 +
In the 10 mm. dogfish embryo there is the first distinct formation of mesenchyme between the splanchnopleure and the endoderm of the oesophagus. The splanchnic mesothelium is closely applied to the endoderm and also extends as a mesentery to become continuous with the somatic layer. The enlargement of the coelom brings about this condition as shown in fig. 10. At this stage the oesophagus is more definitely separated from the myotome and from the mesenchyme, mc. In the uppermost part of the oesophagus near the pharjnix there is a very small amount of mesenchyme, continuous with the head mesenchyme. Longitudinal sections of this region show nothing that can be identified as cells of myotomic origin. The mesenchyme here comes from the splanchnopleure. At A in fig. 10, mid-oesophagus, is a spindle-shaped mesenchyme cell between the endoderm and the mesothelium Fig. 11 is a high power drawing from a section of
 +
 +
 +
30 CAROLINE McGILL
 +
 +
the same embryo, slightly anterior to the one from which fig. 10 was taken. This section shows the origin of two mesenchyme cells from the mesothelium.
 +
 +
In fig. 12 is shown the mid-oesophagus of a 25 mm. dogfish. This is at the region where the limien of the oesophagus is obliterated for a time. In sections both above and below the one pictured no lumen is present. Here quite a thick layer of mesenchyme has differentiated from the mesotheliimi. Longitudinal sections show that this mesenchyme forms in situ. There are no indications that its cells migrate from the myotomes, from which the oesophagus is now completely separated. Longitudinal sections show that in the upper oesophagus little or no mesenchjrme has yet appeared.
 +
 +
The mesenchyme cells of the oesophagus form a complete syncytiiun. They are still connected by wide anastomoses with the mesothelium. From this time on, most of the new formation of the mesenchyme of the oesophagus in this region is by the mitosis of the cells already formed, and not by further differentiation from the mesothelium. In the mesenchymal syncytium of the mid-oesophagus the cells soon begin to differentiate into myoblasts, as shown in Fig. 13.
 +
 +
Pig embryos were not obtained young enough to trace the early formation of the myoblasts. When first studied in a 4 mm. pig embryo, the oesophagus and surrounding region show about the same structiure as seen in the 25 mm. dogfish embryo (fig. 12). In the 4 to 7 nun. pig embryos the oesophagus is surrounded by a thick layer of undifferentiated mesenchyme. There is no indication of a migration of myoblasts from the myotomes into this tissue. As we have seen, it seems highly probable from the study of the early dogfish embrj'o that the myoblasts of the oesophagus arise from the mesenchyme derived from the splanchnopleure, not from the muscle plate, and that there is no downgrowth of the pharyngeal muscle to form oesophageal muscle. The same condition is probably present in the pig embryo.
 +
 +
 +
histogenesis of striated muscle 31
 +
 +
(2) The Transformation of the Mesenchyme into Crossstriated Muscle
 +
 +
(a) Early Development
 +
 +
In the dogfish mid-oesophagus, until the embryo reaches a length of 26 mm., and in the pig embryo until it reaches 5 mm. the tissue outside of the endodermal tube consists of a loose mesenchjTnal syncytium, the origin of which has just been described. The nuclei of the syncytium are round or oval with distinct nuclear wall and chromatin reticulum. From one to three true nucleoli are present in each nucleus, but they are frequently obscured by the chromatin. The protoplasm shows a reticular structuie, the strands of which are made up of fine granules (fig. 12 from a 30 mm. dogfish embryo, and fig. 15 from a 7 nmi. pig embryo).
 +
 +
In this mesenchymal syncytium throughout the entire length of the dogfish oesophagus, and in the upper two-thirds of the pig oesophagus, striated muscle develops. In the lower third of the pig oesophagus smooth muscle develops. The first stage in muscle formation is a general condensation of the mesenchyme at a short distance from the endodermal tube. This begins in the 4 mm. pig embryo, and in the 25 mm. dogfish embryo. The condensation is brought about by a rapid mitotic division of the nuclei, with a corresponding increase in the amount of syncytial cytoplasm. The condensation begins in the mid-oesophagus and extends rapidly both up and down the tube.
 +
 +
The early formation of striated muscle in the oesophagus of both pig and dogfish up to the time the cross striations appear in the fibrillae, is precisely like the development of the smooth muscle of the lower oesophagus of the pig. The two tissues arise from a continuous sheet of mesenchyme. The description given in the writer's paper on the histogenesis of the smooth muscle in the oesophagus of the pig (McGill '07) will therefore apply equally well for the early development of the striated muscle in this region. A comparison of figs. 1 to 21 of the earlier paper with figs. 1 to 17 of the present paper will show this striking similarity. It will be necessary merely to compare the formation
 +
 +
 +
32 CAROLINE MCGILL
 +
 +
of striated muscle with that of smooth muscle already described and to refer the reader to the writer's previous paper for details of the early mj'^ogenesis.
 +
 +
Precisely as in smooth muscle histogenesis, when the formation of striated muscle of the oesophagus begins in the condensed mesenchyme, it is first of all indicated by an elongation of some of the mesenchymal nuclei. For the circular layer of muscle, this begins in the 5 mm. pig embryo. The protoplasm around each nucleus increases in amount and likewise elongates (figs. 16 to 18). Elongation for the formation of the longitudinal layer does not begin in the pig until the embryo reaches a length of 20 mm.
 +
 +
Here, too, as in smooth muscle formation, the statement that muscle arises from undfferentiated mesenchjine is true only for the first few myoblasts formed. In the 15 mm. pig throughout the mesenchyme collagenous fibers appear, as shown by Mallory's stain. Most of the striated muscle arises from this embryonal connective tissue just as does the smooth muscle. Some of the embryonal connective tissue cells in the areas of muscle formation ren^ain undiflferentiated and form the interstitial connective tissue both of smooth and striated muscle.
 +
 +
(6) Increase in the Number of Myoblasts
 +
 +
The increase in the number of myoblasts of striated oesophageal muscle takes place in just the same way as does that of smooth muscle. That is, either by a continuation of the transformation of the embryonal connective tissue cells into myoblasts, or by the mitotic division of myoblasts already formed. Seldom do mitoses occur in the myoblasts after many myofibrillse have appeared.
 +
 +
(c) The Formation of Myofibrillas
 +
 +
Immediately following the elongation of the mesenchymal nuclei, or later, of the embryonal connective tissue nuclei, the myofibrillse arise in the cytoplasm. The myofibrillse, both in the dogfish and in the pig, develop as homogeneous structures without cross-striations. They look exactly like the early
 +
 +
 +
HISTOGENESIS OF STRIATED MUSCLE 33
 +
 +
fibrilte of smooth muscle. This agrees with the observations of Bardeen ('00), Godlewski ('02) and Eycleshymer ('04).
 +
 +
Two varieties of homogeneous myofibrillae form, the coarse and the fine. The coarse myofibrillae arise in the granular cytoplasmic reticulum.. Many of the coarse protoplasmic granules which are present in large numbers at the time the coarse myofibrillae first appear, seem to be of nuclear origin. As the mesenchymal nuclei in the area of muscle formation multiply by mitosis some of the chromatin appears to be left outside in the cytoplasm (figs. 20, 22, 23). These coarse granules become arranged in clumps to form spindle shaped masses. These spindles are usually close to the nuclei (figs. 18 and 21). The granules in the spindles soon fuse to form homogeneous structures. Neighboring spindles unite to form long, varicose fibrillae (fig. 21).
 +
 +
Mlodowska ('08) has described a similar process in skeletal n\uscle. These coarse, varicose fibrillac extend long distances through the protoplasmic syncytium. In the 15 mm. pig embryo some of them extend over half the circumference of the oesophagus. In time the fibrillae become more nearly uniform in caUber (fig. 17). This type of formation of coarse fibrilla? is found only in the early embryo. All subsequent myofibrillje arise as fine fibrillae which later thicken to form uniform coarse fibrillar. The development of coarse myofibrillae begins in the 9 nun. pig embryo (fig. 16) and in the 30 mm. dogfish embryo (fig. 13).
 +
 +
The formation of fine myofibrillae begins in the 25 to 30 mm. pig embryo. Their development is practically Hke that of the fine fibrillae of smooth muscle. In striated muscle, however, all of them later form coarse fibrillae.
 +
 +
In fig. 25 an interesting stage is seen. Here the first formed coarse fibrillae have become cross-striated. Among them are other coarse fibrillae not jet striated, and also numerous fine myofibrillae just arising. On the periphery of the muscle layer is embryonal connective tissue differentiating into muscle. The myofibrillae here arising are fine in the beginning, not coarse as were the first myofibrillae. These fine myofibrillae gradually thicken and finally also become cross-striated. The first-formed coarse and fine myofibrillae correspond vory closely to the coarse
 +
 +
 +
34 CAROLINE MCGILL
 +
 +
and fine fibrillse found in* developing smooth muscle. In fact, in fig. 17 from a section through the upper oesophagus of a 15 nun. pig embryo, the developing cross-striated muscle has precisely the same appearance as has the developing smooth muscle of the lower oesophagus of the same embryo.
 +
 +
The first evidence of cross-striation in the pig was seen in the 13 nmi. embryo in the muscle of the circular layer of the mid-oesophagus. Few of the homogeneous fibrillae however become cross striated before the embryo reaches a length of 25 mm. Crossstriations were seen in the longitudinal muscle layer of the 27 nun. pig embryo. In the dogfish, cross striations appear in the muscle of the oesophagus in embryos between 50 mm. and 60 mm. in length.
 +
 +
In the development of the striated muscle of the oesophagus, just as in the smooth muscle, the myofibrillae arise everywhere in a syncytium. The syncytium in striated muscle persists until a late stage, when it is par ciallybroken up to form the muscle fibers. This takes place when the sarcolenama differentiates from the interstitial connective tissue. Even after the muscle fibers are formed, the syncytium is in part retained, for each muscle fiber is derived from several cells of the original syncytium.
 +
 +
The nuclei seem to take an active part in the formation of myofibrillae. In their division, as already mentioned, they seem to leave at times much chromatin behind in the cytoplasm, and this chromatic material helps to form the first myofibrillae. Then at the time the fibrillae are forming most rapidly the muscle nuclei are filled with deeply staining chromatin (figs. 17 and 22). In all of these early stages the muscle nuclei stain much more deeply than do the connective tissue nuclei, unless the latter be in mitosis. The fact that in their development the myofibrillae begin to arise near the nuclei, and that the spindle-like enlargements of the varicose fibrillae are usually near the nuclei, is also evidence that the nuclei may take part in fibrillar formation. Now and then in early myogenesis some of the muscle nuclei seem to break down completely and liberate their chromatin into the cytoplasm. This chromatin also may possibly take part in fibrillar formation.
 +
 +
 +
HISTOGENESIS OF STRIATED MUSCLE • 35
 +
 +
(d) The Interstitial Connective Tissue
 +
 +
The early formation of the interstitial connective tissue is very similar in the striated muscle of the oesophagus to that already described for the smooth muscle, so the details of development are not given here. The connective tissue arises in situ. In skeletal muscle it does not grow in from the outside as has been described by most recent workers, Bardeen ('00), Godlewski ('02), Eycleshymer ('04), Mlodowska ('08), along with many early investigators. There is also no indication in the histogenesis of oesophageal striated muscle of a degeneration of the forming muscle tissue to allow the ingrowth of the connective tissue, as has been found on skeletal muscle by Mayer ('86), Bardeen COO), Godlewski ('02), Eycleshymer ('04), and Mlodowska ('08).
 +
 +
In development, protoplasmic anastomoses between the muscle cells and the connective tissue cells, are everjrwhere demonstrable (figs. 13, 14, 16, 17, 18, 22 and 24). In this protoplasmic syncytium, myofibrillse and connective tissue fibrillse develop side by side. Later, the collagenous fibrillse are crowded out of the muscle protoplasm by the growth of myofibrillse. Numerous figures from material stained in Mallory's anilin blue connective tissue stain, showing the differentiation of the collagenous and myo-fibrilte side by side, are given in the writer's previous paper.
 +
 +
(e) The Relation of Striated to Smooth Muscle
 +
 +
The origin of the oesophageal muscle as traced in the pig and the dogfish embryo seems to confirm Oppel's statement that the smooth muscle is the primitive muscle of the oesophagus. Oppel arrived at his conclusion from the standpoint of comparative anatomy and phylogeny. In the pig and in the dogfish oesophagus, both tissues as we have seen, arise side by side from the conmion mesenchymal syncytium. Until the cross-striations appear in the fibrillse of the striated muscle, both developing tissues look precisely alike. Smooth muscles may retain nearly this primitive structure in the adult. In the lower oesophagus of the pig the adult muscle retains its syncytial structure and has in places practically the same appearance as the embryonal
 +
 +
 +
36 * CAROLINE MCGILL
 +
 +
syncytium in the formation of cross-striated muscle shown in fig. 17. In most places however, more myofibrilte develop in the smooth muscle syncytium, and there is later in the myofibrillse of smooth muscle a tendency to be grouped to form individual spindle-shaped muscle fibers or cells. As far as I have found, all the transitions from smooth to cross-striated muscle in vertebrates oecm* only in the embryo. There is a possibility, however, that even in the adult manmial, intermediate forms between smooth and cross-striated muscle may occur, as Coakley ('92), described in the human oesophagus. At any rate, in development the two tissues are very closely related.
 +
 +
SUMMARY
 +
 +
1. The tissue destined to form the striated muscle of the oesophagus (dogfish) arises from the splanchnic layer of the mesothelium in the region where this epithelium is in contact with the oesophageal endoderm. Apparently there is no connection at any stage of development between this muscle-forming tissue, which is typical mesenchyme, and the cells of the myotome.
 +
 +
2. The mesenchyme in which striated muscle of the oesophagus forms, in both pig and dogfish, is a complete syncytium.
 +
 +
3. In the 4 mm. pig embryo and in the 25 mm. dogfish embryo there is a condensation of the mesenchyme around the endoderm of the oesophagus. In this condensed mesenchyme the muscle arises.
 +
 +
4. The next step in muscle differentiation is an elongation of some of these mesenchymal nuclei accompanied by an increase in the amount of the surrounding cytoplasm. This begins in the oesophagus of the 5 mm. pig embryo and of the 30 mm. dogfish embryo.
 +
 +
5. After the first formation of muscle, the tissue increases in amount in two ways: (1) by addition of new myoblasts from the mesenchyme without, or by differentiation of interstitial embryonal connective tissue cells into myoblasts; and (2) by mitotic division of the myoblasts already formed.
 +
 +
6. As the nuclei elongate in the muscle-forming tissue the
 +
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HISTOGENESIS OF STRIATED MUSCLE 37
 +
 +
myofibrillse arise in the protoplasmic syncytium. The fibrillae form as homogeneous structures, which later become crossstriated. In first formation they are of two types, coarse and fine.
 +
 +
7. The coarse myofibrillae form first and develop by a massing of protoplasmic granules into irregular spindle-shaped structures. The spindles form near the nuclei. Soon the spindles unite end to end to form varicose fibrillae. The granules fuse and the fibrillae become homogeneous and later of uniform caliber. Shortly after this the cross-striations appear. The coarse myofibrillae arise in the 9 nam. pig embryo and in the 30 mm. dogfish embryo.
 +
 +
8. In the older embryos all of the fibrillae form as fine myofibrillae. These increase in size and later may form coarse myofibrillae.
 +
 +
9. Cross-striations were first distinguished in the oesophagus of the 13 mm. pig embryo and of the 50 mm. dogfish embryo. In the pig, however, only a few fibrillae become striated before the embryo reaches a length of 30 mm.
 +
 +
10. The nuclei appear to play an active part in the formation of myofibrillae.
 +
 +
11. The interstitial connective tissue of the oesophageal striated muscle is fonned in situ from embryonal connective tissue cells, which remain undifferentiated* among the muscle cells. There is thus no necessity for ingrowth of connective tissue such as is described in the histogenesis of skeletal muscle.
 +
 +
12. There is at no stage in the development of the striated muscle of the oesophagus a degeneration of muscle cells such as some investigators have found in the histogenesis of skeletal muscle.
 +
 +
13. The muscle tissue remains a complete syncytium until a comparatively lat^ stage, when the interstitial connective tissue grows rapidly in connection with the formation of the definite cross-striated muscle fibers.
 +
 +
14. The smooth and the cross-striated muscle of the oesophagus arise from a common mesenchymal syncytium. In the early stages, up to the time when the cross-striations form, both tissues appear identical in structm-e. The striated muscle of the oesophagus seems to be only a further differentiation of smooth muscle.
 +
 +
 +
38 CAROLINE MCGILL
 +
 +
No transition forms between the two tissues however were found in the adult oesophagus.
 +
 +
LITERATURE LIST
 +
 +
Balfour. Comparative embryology.
 +
 +
1885 Bardben. The development of the musculature of the body wall in the pig, in 1900 eluding its histogenesis and its relation to the myotomes and to the skeletal and nervous apparatus. Johns Hopkins Hospital Reports, Baltimore, vol. 9.
 +
 +
Born. Dissertation. Berlin.
 +
 +
1873 Calbbrla. Studien iiber die Entwicklung der quergestreiften Muskeln, etc. Ar 1876 chiv /. mikr. Anal., Bd. 11.
 +
 +
CoAKLBT. The arrangement of the muscle fibers of the oesophagus. Researches
 +
 +
1892 of the Loomis Laboratory of the University of the city of New
 +
 +
York, vol. 2. Dahlgren and Kepner. Principles of animal histology.
 +
 +
1908 Eycleshtmer. The cytoplasmic and nuclear changes in the striated muscle cell
 +
 +
1904 of Necturus. Amer. Jour, of AncUomy, vol. 3.
 +
 +
Flint. The organogenesis of the oesophagus. Anal. Am., Bd. 30.
 +
 +
1907 GoDLBwsKi. Die Entwickelung des Skelet-und Hertzmuskelgewebes der Siiuge 1902 thiere. Archiv f. mikr. AtuU., Bd. GO.
 +
 +
Hertwig, O. and R. Die Coelomtheorie, etc. Jena.
 +
 +
1881 Hertwig and Mark. Textbook of embryology.
 +
 +
1892 Herzog. Ueber die Entwicklung der Binnenmuskulatur des Auges. Archiv /.
 +
 +
1902 mikr. Anal., Bd. 60
 +
 +
Ingalls. Beschreibung eines menschlichen Embryos von 4.9 mm. Archiv f. mikr,
 +
 +
1907 Anat., Bd. 70.
 +
 +
K5LUKBR. Gnmdriss der Entwickelungsgeschichte des Menschen, etc. Leipzig.
 +
 +
1884 Lewis and Bardben, Development of the limbs, body-wall and back in man,
 +
 +
1901 Amer. Jour, of Anatomy, vol. 1.
 +
 +
Lewis. Development of the arm in man. Amer. Jour, of Anatomy, vol. 1.
 +
 +
1901 Marchesini and Ferrari. Untersuchungen iiber die glatte und die gestreifte
 +
 +
1895 Muskelfaser. Anat. Am., Bd. 11.
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 +
Maroo. Neue Untersuchungen iiber die Entwickelung, das Wachstum, die Neu 1862 bildung und den feineren Bau der Muskelfasern. Denkschr. d. K
 +
 +
Akad. d. Wiss. Math-Nalur. KL, Bd. 20. Marshall. On the head cavities and associated nerves of el asmobranchs. Quart.
 +
 +
1882 Jour. Micr. Sci., vol. 21.
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HISTOGENESIS OF STRIATED MUSCLE 39
 +
 +
Maurer. Entwickelimg des Muskelsystems und der elektrischen Organe. Hert* 1904 wig's Entwickelungslehr der Wirbelthiere, Bd. 3.
 +
 +
Matxr. Die sogenannten Sarcoplasten. Anat. Am., Bd. 9. 1886
 +
 +
McGiLL. The histogenesis of smooth muscle in the alimentary canal and respira.
 +
 +
1907 tory tract of the pig. Internal. MonaUsckr. /. Anat, u, Phys., Bd24.
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 +
MiNOT. Human embryology.
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 +
1892 Mlodowbka. Zur Histogenesis der Skelettmuskeln. Ext. du. Bull. d. V Acad.
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1908 des Set. de Cracome.
 +
 +
Oppbl. Lehrbuch der vergl. mikrsocopischen Anatomie der Wirbelthiere, Bd. 2
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1897 Remak. Untersuchungen iiber die Entwickelung der Wirbelthiere. Berlin.
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 +
1855 Reutbr. Die Entwickelung der aiisseren Augenmuskulatur beim Schwein. Anat.
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 +
1898 Hefte, Bd. 9.
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 +
ScHULTZE. Ueber MuskelkOrperchen und das, was man eine Zelle zu nennen habe.
 +
 +
1861 Archiv f. Anal. Physiol., etc.
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EXPLANATION OF FIGURES
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Abreyiations
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ao
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aorta
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b ec
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basement membrane of ectoderm
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c
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coelom
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c mf
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coarse myofibrilla
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cnu
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connective tissue nucleus
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cap
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capillary
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 +
ec
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ectoderm
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eel
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embryonal connective tissue
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en
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endoderm
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et
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endothelium
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fmf
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fine myofibrilla
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gmf
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granular myofibrilla
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h
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 +
heart
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m
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 +
myotome
 +
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mc
 +
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mesenchyme
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mil
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 +
mitotic nucleus
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m nu
 +
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 +
muscle nucleus
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ml
 +
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mesothelium
 +
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mu
 +
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 +
muscle
 +
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n
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notochord
 +
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nc
 +
 +
 +
nerve cord
 +
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 +
per
 +
 +
 +
cytoplasmic chromatin
 +
 +
 +
-pa
 +
 +
 +
protoplasmic sync3rtium
 +
 +
 +
smf
 +
 +
 +
cross-striated myofibrilla
 +
 +
 +
spmf
 +
 +
 +
spindle of developing myofibrilla.
 +
 +
 +
40 CAROLINE MCGILL
 +
 +
 +
 +
Fig. 1. Cross-section through the body of a 3 mm. dogfish embryo at level of upper oesophagus. There is no mesenchyme formed. The mesothelial cells, mt* show fine protoplasmic processes, a is a loose cell which appears to be a mesenchyme cell just arising from the mesothelium. Zenker's fluid, iron-hflBmatoxylin. B. and L. oc. 10, obj. 16 mm.
 +
 +
Fig. 2. Cross-section through same embryo as in fig. 1, but taken at the level of mid-oesophagus. The myotome, m, is formed. Between the myotome and the coelomic epithelium, mt, is a strand of loose cells resembling mesenchyme. Zenker's fluid iron-luematoxylin. B. and L. oc. 10, obj. 16 mm.
 +
 +
Fig. 3. A section through the lower oesophagus of the same embryo. The connection of the cavity of the myotome with the coelom is shown. Zenker's fluid, iron-h8Bmatoxylin. B. and L. oc. 10, obj. 16 nun.
 +
 +
Fig. 4. A high power drawing of area X in fig. 1 to show the protoplasmic network extending from the mesothelial cells to the surrounding organs. B. and L. oc. 10, Zeiss 2. mm. 1.30 apochrom. obj.
 +
 +
Fig. 5. A high power drawing of region X in fig. 2. The mesothelial cells are more or less united into a syncytium. B. and L. oc. 10, Zeiss 2. mm. 1.30 apochrom. obj. •
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 +
Fig. 6. A high power drawing of region X in fig. 3. The mesothelial cells are more or less fused leaving only a partially developed coelom. The mesothelium forms two layers, splanchnic and somatic. Protoplasmic processes are numerous. B. and L. oc. 10, Zeiss 2 mm. 1.30 apochrom. obj.
 +
 +
Fig. 13. Section through the mid-oesophageal mesenchyme of a 30 mm. dogfish embryo; b en, basement membrane of endoderm. Just outside this basement membrane is a thick layer of mesenchymal syncytium made up of stellate cells joined by wide protoplasmic anastomoses. At mu, some of the mesenchymal nuclei are elongating to form muscle nuclei; mf, developing myofibrilla. Sublimateacetic, iron-hsematoxylin. B. and L. oc. 10, Zeiss 2 mm. 1.30 apochrom. obj.
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HISTOGENESIS OP STRIATED MUSCLE
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41
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Fig. 5
 +
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^-^r- -i§.n^^'
 +
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42 CAROLINE MCGILL
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Fig. 7. Cross-section of a dogfish embryo 5.5 mm. in length, at the upper oesophagus. The myotome has grown dorsal to the endodermal tube, en. The rest of the mesoderm is represented by the double layer of mesothelium. The coelom is only a narrow slit between the two layers of mesothelium. Zenker's fluid, ironhsBmatoxylin. B. and L. oc. 10, obj. 16 mm.
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Fig. 8. Through mid-oesophagus of a 5.5 nmi. dogfish embryo. The mesoderm s similar to that of the upper oesophagus shown in fig. 7. The blood vessels are growing in, so there is considerable endothelium present, et. B. and L. oc. 10, obj. 16 mm.
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Fig. 9. A high power drawing of area X in fig. 8. The drawing extends from the basement membrane of the endoderm, b en, to that of the ectoderm, b ec* The middle germ layer here is represented by the two layers of mesothelium and the endothelium of the blood vessels. No mesenchyme has formed in the region. B. and L. oc. 10, Zeiss 2 mm. 1.30 apochrom. obj.
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Fig. 10. A section through mid-oesophagus of a 10 mm. dogfish embryo. The endodermal tube is suspended by a double layer of mesothelium. A is a mesenchyme cell differentiating from the splanchnopleure. Considerable mesenchyme has formed between the somatic mesothelium and the body-wall and also around the myotome. The muscle plate is well removed from the oesophagus, h, heart; c, coelomic cavity; ao, aorta. Zenker's fluid, iron-hsBmatoxylin. B. and L. oc. 10, obj. 16 mm.
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Fig. 11. Section through the splanchnic mesothelium and developing mesench3rme of a 10 mm. dogfish embryo near the region shown in fig. 10. At mc are mesenchyme cells which are being formed from the mesothelium. B. and L. oc. 10, Zeiss 2 mm. 1.30 apochrom. obj.
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Fig. 12. Cross-section through the mid-oesophagus of a 25 mm. dogfish embryo. The oesophagus is suspended in the coelomic cavity well separated from the other organs. Here an amount of mesenchyme has formed between the mesothelium and the endoderm. The mesenchyme forms a syncytium. The cells are stellate with round or oval nuclei. Sublimate-acetic, iron-hsematoxylin. B. and L. oc. 5, obj . 6 mm.
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Fig. 14. Section through the circular muscle layer of the mid-oesophagus of a 60 mm. dogfish. Shows various stages in the differentiation of the myofibrills. Cytoplasm forms a complete syncytium. At the margins, the embryonal connective tissue is differentiating into muscle. Sublimate-acetic, iron-hsematoxylin. B. and L. oc. 10, Zeiss 2 mm. 1.30 apochrom. obj.
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HISTOGENESIS OF STRIATED MUSCLE
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43
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ben
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nit
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F.g. 11
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Fig. 14
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44 CAROLINE MCGILL
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Fig. 15. Cross-section through the oesophagus and surrounding tissue of a 7 mm. pig. embryo. Note the condensed mesenchymal syncytium with a few of the nuclei concentrically arranged, h v, blood vessel; ir, trachea; oes, oesophagus. Zenker's fluid, iron-haematoxylin. Zeiss oc. 4, obj. D.
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Fio. 16. Section through a portion of the CBSophagus of a 10 mm. pig embryo. This shows the condensation of the cytoplasm and elongation of mesenchymal nuclei to form the circular muscle coat, g mf, coarse cytoplasmic granules arranging in rows, the first indication of the coarse myofibrillse. mil, shows mitosis in the muscle-forming tissue. Zenker's fluid, iron-haematoxylin. Zeiss comp. oc. 8, 2 mm. 1.30 apochrom. obj.
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Fig. 18. Small portion of the muscle syncytium from the oesophagus of a 13 mm. pig embryo showing the origin of the coarse myofibrillae from the granular reticulum, gmfy is a mass of coarse chromatic (?) granules; at sp mf, the granules have almost completely fused to form a homogeneous, spindle-shaped mass, a shows a granular strand connecting this spindle with another smaller one. 6 is a myofibrilla arising in part in the protoplasm of an interstitial connective tissue cell. Zenker's fluid, iron-haematoxylin. Zeiss comp. oc. 12, 2 mm. 1.30 apochrom. obj.
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Fig. 19. A nucleus from muscle-forming tissue in the oesophagus of a 13 mn^. pig, in prophase of mitosis. It shows the large deeply staining chromosomes. Zeiss comp. oc. 8, 2 mm. 1.30 apochrom. obj.
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Fig. 20. A nucleus from the same section as that shown in fig. 19, undergoing mitosis. A large amount of chromatin (p cr) apparently has not entered the spindle but remains outside in the cytoplasm. Zeiss comp. oc. 8, 2 mm. 1.30 apochrom. obj.
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Fig. 21. From the same region asfig. 20. This shows the formation of a coarse myofibrilla by the union of spindles near several nuclei. This gives the varicose appearance. Zeiss 6omp. oc. 12, 2 mm. 1.30 apochrom. obj.
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Fig. 23. Two mitotic nuclei from the region of muscle formation in the oesophagus of a 13 mm. pig embryo. Nucleus a is in prophase and shows a large amount of chromatin. Nucleus b is in telophase. Many chromatic granules are apparently left in the cytoplasm. Zenker's fluid, iron-hsematoxylin. Zeiss comp. oc. 8, 2 mm, 1.30 apochrom. obj.
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Fig. 24. Muscle tissue from the oesophagus of a 13 mm. pig embryo. The coarse myofibrilla at 8 mf is beginning to show cross striations. Zenker's fluid, ironhsematoxylin. Zeiss comp. oc. 8, 2 mm. 1.30 aprochrom. obj.
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HISTOGENESIS OP STRIATED MUSCLE
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•JK-***?*^' *V a"^^ «'*^ *'Vifc .^ -*. ^ * * • .a * ■■-•••*
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45
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46 CAROLINE MCGILL
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Fig. 17. Through a portion of the wall of the OBsophagus of a 16 mm. pig embryo near bifurcation of trachea to show area of cross-striated muscle formation. Cytoplasmic syncytium everywhere present. The myofibrillaB show in various stages of development, p cr, chromatic (?) granules free in the protoplasm. The coarse myofibrilla, c m/, ran over one-half way around the oesophagus. Many of the fine fibrils visible in the mesenchyme are collagenous fibrils which can be differentiated with Mallory's anilin blue connective tissue stain. Zenker's fluid, ironhsematoxylin. Zeiss comp. oc. 12, 2 mm. 1.30 apochrom. obj.
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Fig. 22. The muscle syncytium from the mid-oesophagus of a 16 mm. pig embryo. The large amount of chromatin (?) in the protoplasmic syncytium is noticeable, -per. The muscle nuclei stain very intensely. Zenker's fluid, iron-hsematoxylin. B. and L. oc. 10, Zeiss 2 mm. 1.30 apochrom. obj.
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Fig. 26. A section through the inner part of the circular muscle layer of a 27 mm. pig oesophagus. This section shows a number of stages in the formation of myofibrillae. The oldest fibrillae are cross-striated, s mf, c m/ is a coarse myofibrilla only in part striated. / m/ are fine fibrillse just arising. In the adjacent embryonal connective tissue numerous cells are elongating to form muscle. With Mallory's anilin blue connective tissue stain, these cells are found to contain both myofibrillse and collagenous fibrils. Cap is a capillary. Zeiss comp. oc. 8, 2 mm. 1.30 apochrom. obj.
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HISTOGENESIS OF STRIATED MUSCLE
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47
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Fig. 17 Gmf mc
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^"^'^^^ ■ -fy^f
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m
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cap
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Fig. 25
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BOOK REVIEW
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A Text-Book of Anatomy. Edited by D. J. Cunningham, F.R.S. Third Edition, 1909. New York: William Wood and Company.
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The revision of the third edition of Cunningham's Text-Book of Anatomy was the last labor of its distinguished editor. The style and plan of the third edition remain the same as in previous editions. The sections on Osteology and Myology have been largely rewritten and the descriptive matter altered to conform to the BNA terminology and much has been gained thereby in clearness of style and conciseness of expression. It is to be hoped that the remaining sections of the book will undergo revision in the near future and the use of the BNA nomenclature consistently followed.
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The number of pages in the section on Osteology remain the same as in the second edition, with thirty-four additional illustrations. In the description of the bones of the extremities new drawings are introduced, delineating in color the origin and insertion of the muscles. The bones entering into the construction of the skull as a whole, and in different planes of section viewed from various aspects, have been differentiated in this manner. Color likewise has been used to distinguish the articular surfaces of the bones of the hand and foot. There are several new radiographs of the foetal hand and foot.
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Appended to the section on Osteology are six short but comprehensive accounts of: (A) Architecture of the bones of the skeleton; (B) Variations of the skeleton; (C) Serial homology of the vertebrse; (D) Measurements and indices employed in physical anthropology; (E) Development of the chondrocranium and morphology of the skull; (F) Morphology of the limbs.
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The number of pages in the section on Myology are slightly increased and the new drawings are excellently executed. Many of these in their handling and representation show the influence of Spalteholz's Atlas. Of the drawings of the sole of the foot, three are taken from the left side and one from the right. Further, figures 294 and 301 are placed on the page with the digital extremities away from the observer, while figures 303 and 304 have a reversed position. The same discrepancy exists in the representation of the palmar aspect of the hand. The figures do not show clearly the manner of insertion of the flexor tendons and their disposition after entering the flexor sheaths.
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A "Glossary of Anatomical Terminology" is prefaced to the introduction, giving a short historical account of the Basle Nomina Anatomica.
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Henry W. Stiles.
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PRELIMINARY PROGRAMME
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Of the II. International Anatomical Congress, Brussels, August 7-11, 1910.
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SUNDAY, august 7
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4:30 p.m. Session of the committee, consisting of the presidents and secretaries of the five united societies, and also the president and secretary of the local committee, to be held in the Anatomical Laboratory, Park Leopold: entrances rue Belliard and rue du Walbeck.
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8 :30 p.m. Welcome in a place to be announced.
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MONDAY, 8th; THURSDAY, 11th.
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Mommgs, from 9 to 1. Sessions.
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Afternoons, from 3 to 6. Demonstrations.
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The scientific sessions will take place in the auditorium of the Physical Institute of the University, 14 rue des Sols.
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The demonstrations will be held in the Physical Institute, Park Leopold.
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The local committee consists of Messrs. Rommelaere, president of the Administrative Council of the University; Paul Ererra, Rector of the University, and Raoul Warocque, the founder of the Anatomical Institute, as honorary president. Professor Brachet as president, and Professor Joris as vice president.
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Committee on Lodgings : Dr. Brunin, Chef des travaux (Anatomie) .
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Information concerning anatomy, comparative anatomy, and embryology may be obtained from Professor Brachet, rue Sneessens 18; for histology. Professor Joris, rue de President 73.
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A banquet is proposed for Wednesday, August 10.
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SYMPOSIUM ON COMPARATIVE NEUROLOGY^
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1. THE PHYLOGENETIC ORIGIN OF THE NERVOUS
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SYSTEM
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G. H. PARKER
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Harvard University
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The highly differentiated nervous system, such as is f oimd in the vertebrates and other higher metazoans, is described as composed for the most part of many inter-related reflex arcs. Each of these arcs involves at least three parts: a sense organ or receptor which receives the external stimulus and originates the nervous impulse; a central nervous organ or adjustor in which the impulse may be variously modified and directed; and a muscle, gland, or other effector by which the animal responds to the external stimulus. Nerve fibers connect, of course, the receptor with the central apparatus and the latter with the effector. At least two classes of neurones are concerned in this mechanism, one afferent or sensory and the other efferent and usually motor. The sensory neurone is modified at its peripheral end to form the receptor and its nerve fiber extends as a rule to the central organ in which it ramifies; its cell-body may occupy a peripheral position even forming an essential part of a sense organ as in many invertebrates and in the olfactory organ of vertebrates, or it may be nearly central in location as in the spinal ganglia of the vertebrates. The motor neurone has its cell-body within the central organ and its fiber as an efferent fiber extends to a muscle where it terminates. Besides these two classes of neurones, afferent and efferent, the central organs usually contain a vast congregation of correlation neurones which in one way or another intervene between those already mentioned.
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^Presented at the twenty-fifth session of the American Association of Anatomists, Boston, December, 1909.
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52 G. H. PARKER
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Such a nervous system as the one just described is found in the vertebrates, moUusks, anthropods, worms, and other higher metazoans, but is only feebly represented, if in fact it can be said to be represented at all, in the echinoderms, ctenophores, and coelenterates. The part that is least developed in these lower animals is the central organ, and, though this part cannot always be said to be absolutely unrepresented, it is so deficient, especially in the coelenterates, as to have led to the designation of their nervous apparatus as diffuse rather than centralized. The so-called diffuse nervous system of these animals is the simplest nervous system with which we are acquainted, for, notwithstanding repeated efforts, no true nervous structure has ever been demonstrated in those metazoans which, like the sponges, are more primitive than the coelenterates. If, therefore, the beginnings of the nervous system are to be sought for, attention must be directed to the coelenterates.
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The coelenterate body is composed chiefly of two specialized epithelial layers, ectoderm and entoderm, each of which contains both nervous and muscular elements. The nervous elements are epethelial sense-cells whose receptive ends are at the periphery of the layer in which they are contained and whose nervous ends form a system of extremely fine interlacing branches many of which are probably directly* connected with the deep-seated muscle-cells. The fine branches from many neighboring sense-cells establish what is probably a true nervous net by which transmission is accomplished not only to the subjacent muscle-cells but to those some distance away. Here and there this net contains conspicuous, multipolar cells which contribute fibrils to it and which for this reason are believed to be nervous. It is with the origin of this relatively simple neuromuscular mechanism that we are concerned.
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In 1872 Kleinenberg announced the discovery in the fresh-water hydra of what he designated as the neuromuscular cell. The peripheral end of this cell was situated on the exposed surface of the epithelium of which it was a part and was believed to act as a nervous receptor; the deep end was drawn out into a muscular process and served as an effector to which transmission was supposed to be accomplished through the body of the cell. Each such cell was
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THE PHYLOGENETIC ORIGIN OF THE NERVOUS SYSTEM 53
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regarded as a complete and independent neuromuscular mechanism, and the movements of an animal provided with these cells were believed to depend upon the simultaneous stimulation of many such elements. It was Kleinenberg's opinion that these neuromuscular cells divided and thus gave rise to the nerve-cells and muscle-cells of the higher animals. In fact he declared that the nervous and muscular systems of these animals were thus to be traced back to the single type of cell, the neuromuscular cell, which morphologically and physiologically represented the beginnings of both.
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Some years later, in 1878, the Hertwigs published an account of the minute structure of the coelenterate nervous system and showed thatKleinenberg's so-called neuromuscular cells were probably merely muscle-cells in process of differentiation. They consequently proposed for these cells the more appropriate name of epithelio-muscle cell. They also claimed that in the evolution of the neuromuscular mechanism in coelenterates the three types of cells that they had identified, the sense-cells, ganglion-cells, and muscle-cells, were simultaneously differentiated from ordinary epithelial cells. Thus these three elements, though regarded as derived from a common layer, were, according to the Hertwigs, not the descendents of any single type of cell such as the neuromuscular cell.
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Although Kleinenberg's theory and the theory of the Hertwigs differ in certain important details, they agree in declaring for the simultaneous and interrelated evolution of nerve and muscle. As contrasted with this view is the hypothesis that was first advocated by Claus and later by Chun that the two types of tissue arose independently and became secondarily united. In 1880 Chun called attention to the fact that in vertebrates the motor nerve-fibers grow out of the medullary tube and become connected with the muscles secondarily and he regarded this as evidence that nerve and muscle had arisen in phylogeny independently and had become secondarily united. But the majority of investigators have sided with the opinion expressed by Samassa (1892) that a nervous system purely receptive in function and without effectors of any kind is practically inconceivable. Hence the hypothesis of Claus and Chun has been generally regarded as untenable.
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54 G. H. PARKER
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The current opinion among investigators as to the evolution of the nervous system of primitive metazoans remains essentially that of the Hertwigs, namely that nerve and muscle have been differentiated simultaneously and in close physiological interrelation but from cells which were separate members of an epithelium. To this view I wish to oflfer certain opposing facts obtained from a study of sponges. It has already been stated that no nervous structures have been definitely identified in the sponge, nor is there, so far as I am aware, any physiological reason to suppose that such exist. Nevertheless these animals are capable of some movements and their movements are so related to changes in the environment as to be classed as normal reactions. Under this head may be placed the closing and opening of the oscula and of the pores, and certain general movements of the whole body of the sponge. The closing of the oscula and of the pores is carried out by sphincters composed of spindle-shaped cells which in many respects resemble smooth muscle-fibers. These cells are unprovided with nerves and are brought into action, so far as I have been able to ascertain, by direct stimulation. I therefore believe them to be independent effectors and that the sponge is an example of an animal that possesses muscle but no nerve. If, as seems probable, muscle without nerve exists in these primitive metazoans, it follows that we are no longer justified in concluding that nerve and muscle have differentiated simultaneously, but it must be admitted that muscle is phylogenetically the older. I therefore believe that the beginning of the neuromuscular mechanism is to be found in the appearance of independent effectors such as muscles and that sponges probably represent this initial stage in the evolution of the mechanism concerned. Some physiologists may be inclined to question the actual occurrence of normally independent effectors, but the heart of Salpa, and that of the chick embryo before it becomes invaded by nervous tissue are examples of this kind, and it is now well known that though the sphincter pupillae of the vertebrate eye is under the control of nerves, it also responds directly to light. These instances seem to me a sufficient warrant for a belief in the existence of independent effectors.
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Although the sphincters of sponges are effectors without nerves,
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THE PHYLOGENETIC ORIGIN OF THE NERVOUS SYSTEM 65
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they are good examples of the kmd of centers around which nervous tissue probably first arose. This development can be conceived to have occurred in the epithelial cells in the immediate proximity to such a center, in that these cells gradually assumed a special receptive function whereby they could stimulate the adjacent muscle more efficiently than it could be stimulated directly and thus an ordinary epithelial cell would gradually be converted into a receptive or sense-cell. From this standpoint the original function of the sense-cell was merely that of a delicate trigger by which the muscle would be more certainly and efficiently brought into action than through its own receptive capacity and many sense-cells in the lower metazoans probably still retain this as their sole function. Such cells occur abundantly in the coelenterates and hence I regard the sense-cell as the first type of nervous tissue to be differentiated. Since sense-cells and muscle-cells make up the chief part of the neuromuscular apparatus of coelenterates, I have designated this apparatus as a receptor-effector system.
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But coelenterates usually show more than a simple receptoreffector system, for the fine branches from their sense-cells not only reach their muscle-cells but also anastomose with one another and form a nervous net. Such a net is the first step toward the formation of a central nervous organ or adjustor and its origin in relation to the sense-cells and the muscle-cells is probably so strictly local that it practically realizes Hensen'sview as to the histogenetic relations of nerve and muscle, namely that these elements are not developed separately and brought into connection secondarily, but that their connections are original and give evidence of the incompleteness of cell division in the course of ontogeny. Such nets serve as more or less diffuse transmitters and are supplemented by the fibrils from certain contained cells, the so-called ganglion cells, which have migrated into the net and which probably mark the first step in the growth of those accumulations of cell-bodies that characterize the central nervous organs of the higher animals.
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If this view as to the mode of origin of the central nervous organs is correct, it follows that these organs myst be controlled in their incipiency by the sense organs. In such coelenterates as sea anemones where the sensory specialization is slight, there is scarcely
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56 G. H. PARKER
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any evidence of centralization in the nervous net, but in jelly fishes where the sense organs are specialized and in groups, each group has associated with it a region of special development, an incipient central organ in the nervous net. In bilateral animals such as the annelids and the crustaceans, the chief portion of the central nervous system, the so-called brain, is also associated with a group of sense organs and these organs, essential to the anterior end of any animal that moves forward, determine, in my opinion, the position of the brain rather than the reverse. Even in the vertebrates where the brain arises to a dignity not attained by any other nervous organ, its anterior position has been determined, I believe, by the location of the sense organs rather than that the sense organs are at the anterior end because the brain is there.
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But although the central nervous organs have probably developed from a nervous net under the influence of the sense organs, they have taken in their later evolution a course more or less their own. Even the nervous net, which, in my opinion, unquestionably exists in the lower metazoans, has been denied in the central nervous organs of the higher animals. But it is not impossible that in these more specialized forms a nervous net may have a local existence. Evidence that nervous nets do not exist in certain parts of the vertebrate nervous system does not prove that they may not occur in other parts of this system. In the myenteric plexus of the vertebrate intestine the relations of nerve and muscle are such as to recall most strikingly the conditions already portrayed in the nervous net and muscles of the coelenterates and it is possible that nervous transmission in these animals follows the same rules that it does in the vertebrate intestine. In the vertebrate retina, too, the histological evidence is strongly in favor of a nervous net and the fact that the cells of the retina are members of the same epithelial layer and may therefore always have retained primary connections, suggests a fundamental similarity with the conditions in the coelenterates. Thus there are localities in the nervous systems of even the most highly differentiated animals where these most primitive of central structures, the nervous nets, very probably occur. But to claim on the basis of these instances that the whole central nervous system of the vertebrate is con
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THE PHTLOGENETIC ORIGIN OF THE NERVOUS SYSTEM 57
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structed on the plan of a nervous net would be going far beyond the facts.
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It is well established that in the histogenesis of the central nervous organs of the higher animals, many cells that are ultimately in most intimate physiological relations, are in their early stages of development far asunder and that they attain to their final close relations by throwing out processes that grow toward one another. It is probable that these processes never really unite into continuous transmitting tracts but retain at least a certain physiological separateness, for in such parts of the central organ where these relations occur, transmission is not diffuse, as in the nervous net, but is limited to a single directon. Central nervous systems having these peculiarities have been called synaptic because the contact points between their cells, the synapses, are believed to be the parts that in some way govern the direction of transmission. This synaptic system has in the higher animals replaced to a considerable extent the more primitive nervous net and though this nervous net may still exist in some parts of the central nervous apparatus of such animals as the vertebrates, it is not the structure that gives to these organs their distinguishing characteristic. In these organs the fully differentiated nerve-cell or neurone with its synaptic connections is the characteristic structural unit of the system. Combinations of such imits make up large parts of the central nervous organs of the higher animals and possess apparently physiological possibilities of a vastly higher order than can be found in the more primitive nervous nets; they have thus afforded the structural basis for the nervous activities of all the higher animals. Although the nervous net with its capacity for diffuse transmission was the structure in which the central nervous system took its origin, I nevertheless believe that this system early underwent fundamental changes whereby synaptic neurones with transmission in restricted directions replaced in large part the more primitive system of diffuse nervous nets.
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The facts briefly stated in the preceding paragraphs justify the conclusion, I believe, that muscular tissue and nervous tissue have not arisen at the same time phylogenetically, but that muscle in the form of independent effectors preceded nerve in its develop
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58 G. H. PARKER
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ment and that nervous tissue differentiated in close proximity to muscle tissue as groups of sense-cells or receptors. Still later central nervous organs developed between the receptors and the effectors, first as clusters of nerve or ganglion cells which added to the nervous nets and later as aggregates of synaptic neurones from which were formed the more complex nervous organs of the higher anmals. Thus the three parts of the dijBferentiated neuromuscular system of the higher animals have, in my opinion, developed in sequence: first, the muscle or effector; next, the senseorgan or receptor; and last, the central organ or adjustor.
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2. THE RELATIONS OF THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS IN PHYLOGENY
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C. JUDSON HERRICK
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University of Chicago WITH TWO TEXT FIGURES
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The fundamental factors in the diflferentiation of nervous and non-nervous tissues have been clelarly presented by Dr. Parker, whose researches have the great and rare merit of combining both anatomical and physiological view-points and methods.
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I commented yesterday* upon the striking parallelism between the series of animals when arranged according to structure by the comparative anatomists and the series when arranged according to functional type by students of animal behavior, and I pointed out that the ventral segmented ladder type of central nervous system, as seen in annelid worms and arthropods, naturally by virtue of its structure expresses itself in rigidly predetermined or stereotyped instinctive behavior, while the dorsal tubular and imperfectly segmented nervous system of vertebrates is structurally adapted to serve both reflexes and instincts as in arthropods and also the more plastic individual reactions of the intelligent type. The pre-eminence of vertebrates in the ability to perform individually acquired intelligent acts not predetermined in the hereditary nervous pattern is due primarily, I maintain, to the mechanical advantages of the tubular nervous system as compared with the ladder type of nervous system in the elaboration of correlation tissue, and I wish now to illustrate this thesis somewhat more fully from the anatomical side.
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Let us take as our point of departure a very simple metazoan
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' The Evolution of Intelligence and its Organs. Address of the vice-president and chairman of Section F, Zodlogy, of the American Associatior for the Advancement of Science. Science, N. S., vol. 31, No. 784, pp. 7-18, Jan., 1910.
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60 C. JUDSON HERRICK
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body with a differentiated head end, bilateral symmetry and a diffuse or very imperfectly centralized nervous system, such an animal, say as a tiu'bellarian worm (Fig. 1), which habitually creeps upon the ground. Within the outer epitheUum is a layer of locomotor musculature (M) and a central digestive tract (G) and between these the other organs of vegetative life. Outside impressions are received chiefly by contact stimuli; and the diffuse nervous system is concerned for the most part with these stimuli and with internal or visceral reactions. The dorsal epithelium (SEN) alone is exposed to any considerable number of stimuli from distant objects, such as Ught and heat rays, currents and vibratory disturbances in the surrounding medium, emanations of odorous particles, etc. This animal can respond to a very small number of such stimuli. If such a species continues to crawl upon
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SCN.
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Fig. 1
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or within the mud, after the manner of the worm-like ancestors of the arthropods, the contact receptors, especially those of the ventral and lateral surfaces, will in the course of evolution become more highly developed and the diffuse nervous system is naturally concentrated into a ventral central nervous system contiguous to these receptors. This vermiform locomotion and the associated transverse segmentation have in fact so firmly fixed the ventral ladder tjrpe of nervous system in the articulate phylum that even the free swinaming crustaceans and the insects depart but little from it.
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If, however, the hypothetical ancestral species with a diffuse nervous system assumes from the start a free swimming habit, this will tend to promote the differentiation of the dorsal distance receptors rather than the ventral contact receptors. That is, the
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THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS 61
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stimulation complex which reaches this free swimming body will contain a relatively smaller proportion of elements aflfecting the ventral and lateral body surfaces by contact and a larger proportion of elements emanating from distant objects and reaching the dorsal and oral surfaces.
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Not only has such a differentiation of the dorsal epithelium undoubtedly taken place in ancestral vertebrates, but the primary correlation centers for these receptors have also been derived from the same source, and ultimately the correlation centers for the greater part of the contact and visceral reactions came to be incorporated with them, only the peripheral sympathetic system retaining the primary diffuse formation.
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Sherrington has shown^ that the mammahan cerebral cortex has been elaborated largely to serve the distance receptors; I think that we may carry the idea further back and say that the entire vertebrate central nervous system was from its earliest inception differentiated away from the anneUd and arthropod tjrpe under the same influence.
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A difference in habitual reaction to the common environmental forces on the part of a primitive animal with a diffuse and undifferentiated nervous system may, therefore, be said to have set the direction of two divergent lines of adaptation, one culminating in insects with (predominantly) instinctive action systems, the other culminating in primates characterized by individually adaptive and intelligent actions. The ultimate explanation for this divergence goes back, as in the case of all other evolutionary movements, to differences in the animaUs reactions to the environment. Once the structural pattern has been thus laid down and fixed in the hereditary machinery, perhaps by natural selection, the future course of evolution is in some measure predetermined by the structural possibiUties of the organs so differentiated. Thus, the ventral ladder type of nervous system favors the differentiation of an instinctive type of behavior based fundamentally on segmental reflexes, while the dorsal tubular type is better adapted for the development of longitudinally arranged correlation tissue which
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The Tntegrative Function of the Nervous System. New York, 1906
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62 C. JUDSON HERRICK
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facilitates total rather than segmental responses and a higher degree of integration of the whole system. Here I think we have clearly the machinery of a certain kind of determinate evolution which contains no elements of mysticism but rests on an intelligible basis of inherited tjrpe of nervous organization and action system.
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Herbert Spencer's definition of life is biologically sound in that he makes the measure of correlation of internal with external forces the criterion of life. The lowly organism touches the environment at few points, receives but little from it and gives but little back. With the increase in the range of this effective contact with outer forces, the mechanism of internal regulation necessar* ily becomes more complex. Thus we have from the beginning of dififerentiation the somatic or exteroceptive activities set over against the visceral or interoceptive.
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This finds its anatomical expression in two fundamentally distinct types of reflex arcs: (1) the somatic system, comprising the peripheral or exteroceptive sense organs, somatic sensory nerves and cerebral centers and somatic motor centers and peripheral nerves ending in the skeletal muscles, the whole system serving those reactions which the animal makes in response to external stimuli. (2) The visceral system, comprising the sense organs of the viscera, termed interoceptors by Sherrington, the visceral sensory nerves and centers and the visceral efferent centers and peripheral nerves, terminating in visceral muscles, glands, etc. The coordinating centers of the visceral system are partly peripheral in the sympathetic ganglia and partly in the central nervous system; those of the somatic system are wholly central.
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In the central nervous system, then, we find evidences more or less clearly preserved of four fundamental longitudinal colmnns on each side of the body. These are so arranged that as one passes from the dorsal toward the ventral side of the neural tube in cross section he meets first the somatic sensory centers, then the visceral sensory, the visceral motor and the somatic motor. The relations of the four primary longitudinal columns of the central nervous system to the dorsal ectoderm will next be considered.
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In all vertebrate embryos we find the dorsal nervous tissue at
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THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS
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63
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the appropriate stage in the form shown m Fig. 2, the mid-dorsal epithelium being in process of invagination to form the neural tube. The figure is pinrely schematic and includes some features which are clearly differentiated only in later developmental stages. The somatic sensory surface (exteroceptors of Sherrington) includes both specialiaed sensilte (SEN) and general sensory endings widely distributed in and imder the epidermis. At the Up of the neural groove is the neural crest tissue (N.C), from which the spinal ganglion cells will arise. These receptive cells sometimes, however, remain in the outer epithelium, either permanently, as in the olfactory organ, or temporarily, as in the gan
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SEN.
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Rg. 2
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glionic elements which are added to the cranial nerve ganglia from the embryonic cutaneous placodes. In other cases they are incorporated in the neural tube, as in the giant cells of. the spinal cord of some fishes and the retina.
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In the walls of the neural tube the dorsal part becomes the primary sensory centers, and separated from it by a very constant longitudinal groove, the sulcus limitans (S.L.) the ventral part becomes the primary motor centers. These are further subdivided, the somatic sensory centers (exteroceptors and proprioceptors of Sherrington) lying dorsally close to the neural crest and outer skin, the somatic motor far ventrally close to the myotomes and
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64 C. JUDSON HERRICK
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the visceral sensory and motor between. These four primary functional columns can be more or less clearly recognized on each side of the neural tube in all vertebrates. This arrangement, while very different from that of arthropods, is per se no better adapted for higher psychic manifestations. But in later embryonic stages, to these primary centers there is added* the correlation tissue of the reticular formation and the suprasegmental centers; and we have the key to the greater potentiality of the vertebrate tjrpe in the favorable form of the tubular nervous system, as contrasted with the ladder type, for the elaboration of this tissue.
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The organs of somatic response in vertebrates are themselves so very complex as to require a special coordinating machinery of their own, such as muscle spindles, sensory endings of tendons, joints, etc. These, with their cerebral centers and return pathways, are termed by Sherrington the proprioceptive reflex apparatus. It is genetically and anatomically subsidiary to the exteroceptive system. Besides the sense organs within the somatic muscles, etc., mentioned above, this system includes the organs of the labyrinth of the internal ear and the associated cerebral centers of equilibration and muscular coordination. The cerebellum has been developed from the somatic sensory column of the medulla oblongata as the chief central coordinating apparatus of the proprioceptive system. The somatic system of reflex arcs is, accordingly, divided into exteroceptive and proprioceptive systems, whose receptors and cerebral centers are distinct, but whose efferent pathways are the same — to the somatic muscles in both cases.
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The exteroceptors are further subdivided into contact receptors (organs of touch, etc.), and distance receptors (such as the eye and ear) the former being stimulated by objects at the body surface, the latter by forces emanating from distant objects. Evidently the tjrpe of reaction must necessarily be very different in the two cases.
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The anatomical structure of the vertebrate central nervous system has been molded under the influence of two factors which have often been antagonistic. The first of these is the primary bodily metamerism, in accordance with which each segmental
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At the Baltimore Meeting of the Anatomists in 1908, several anatomists interested in the study of human embryology decided that it is desirable to publish a list of the human embryos found in our various laboratories, in the Anatomical Record. It is believed that this list will be not only of great value to those who are conducting studies in the anatomy of the human embryo but also will encourage others to collect embryos and make them available for scientific research.
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The list now prepared includes those embryos in the principal collections, but it is desirable to make it as complete as possible. Those who have specimens which they wish to include in this catalogue are requested to send the data, as indicated below, to Dr. F. P. Mall, Johns Hopkins University, Baltimore, within the next few weeks.
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List of Human Embryos in the Collection of
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No. of Embryo
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No. of Slides in Series
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Crown Rump Length
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in millmeters
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Fresh
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Formalin
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Alcohol
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Clearing fluid
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On slide
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Remarks
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( T. Transvenie
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Direction of Section ^ s. sagituu
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[ F. FroDtal
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Thickness of Sections in microns Stains
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r E. Excellent
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Condition of tissues | ^ ^^
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I p. Poor
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THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS 65
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nerve tends to repeat exactly the same arrangement of components. This is far more evident in the lower vertebrates than in the higher, though it is never so important a factor as in the annelid worms and most articulata. This factor is more and more completely obscm'cd as we ascend the vertebrate series by the second factor, viz., the longitudinal integration and correlation of the several functional systems which we have enumerated above. The more highly developed functional systems tend to be structurally more perfectly unified and concentrated, and this disturbs both the metameric and the longitudinal patterns. Examples of this sort of disturbance are found in the tendency of all of the cutaneous nerves of the head to enter by the trigeminus and of the vagus to absorb the visceral components. In the rostral end of the brain the development of the massive suprasegmental correlation centers disturbs the primitive relations still more. But the primary pattern as we have outlined it is clearly evident in the structure of the medulla oblongata (either adult or embryonic) and its nerves in all vertebrates, and the comparative morphology of this part of the nervous system may be regarded as definitely established in its main features. The history of the steps by which this correlation has been effected would be an interesting contribution to scientific method.
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After the formulation of Bell's law of the sensory character of the dorsal spinal roots and the motor character of the ventral roots, morphologists were long absorbed in the vain attempt to reduce the cerebral nerves to a similar simple segmental scheme. Even after Gaskell and His had laid the foundation for a true morphology of the medulla oblongata and its nerves, the deceptive simplicity of the older metameric schemata still domhiated the field and misled some of our ablest anatomists and embryologists.
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As anatomists we have been slow to recognize the importance to our work of certain facts which have long been physiologically obvious. It was not until members of our own number, working with anatomical methods, brought out the structural pattern of the nervous system in some of the lower vertebrates where it presents almost diagranmiatic simplicity, that we have directed our attention to them.
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66 C. JUDSON HERRICK
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For four hundred years the cranial nerves had been dissected and for fifty years their central courses had been studied microscopically before any one succeeded in effecting a precise correlation of the peripheral with the central courses by following the nerve roots accurately through the ganghonic plexuses, and thus making an anatomical demonstration of the composition of the reflex arcs known physiologically to be there represented.
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Acting under the stimulus of a suggestion made by Professor H. F. Osbom in 1888, a small group of American neurologists has patiently unravelled the tangled threads of the cranial ganglionic complexes in representative vertebrates, and now we are able to formulate a structinral paradigm or t jrpe form of cerebral nerve components for the vertebrates as a class. The completion of the picture by the addition of f inrther anatomical details, especially as to the corresponding central relations, by embryological studies and by physiological experimentation is rapidly progressing. This doctrine of nerve components, though first formulated in anatomical terms, is essentially a physiological conception, defining the peripheral and central pathways of the great fundamental types of reflexes, as I have endeavored to show by placing the emphasis on the physiological side and by the use, in this discussion, so far as possible, of the luminous terminology of Sherrington.
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That the fimdamental pattern of the vertebrate nervous system, as here laid down in terms of functional systems, is scientifically true is shown by the essential harmony of the data developed, for the most part entirely independently, in the fields of comparative anatomy, physiology and embryology. Conversely the most recent and perhaps the most striking illustration of the clarifying influence of these physiological units upon vexed morphological questions is given by the work of Landacre to be reported in this symposium.
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The whole ectoderm of the vertebrate embryo, particularly on the dorsal side, must be regarded as potentially nervous. Part of this tissue is incorporated into the neural tube, a part is used to form the neural crest and peripheral neurones and a part develops sensory functions in situ peripherally. The relations of the peripheral receptive cells to the parent ectoderm are various. Prim
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THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS 67
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itively these receptors were in the epidermis and some retain this position throughout the whole course of the phylogeny, as in the case of certain elements in the skin of annelid worms and of Amphioxus and in the vertebrate olfactory organ.
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The general cutaneous innervation in lower forms is responsive to a considerable variety of stimuli. Even the human skin has several very different sensation qualities whose physiological analysis has proven very difficult, and it is still uncertain whether all of these qualities are served by specifically different nerve fibers or whether the analysis is in part central. The whole skin is very sensitive to chemical stimuli in fishes and in man it has been shown that general sensory nerves, not belonging to the gustatory system, are sensitive to certain chemical stimuli wherever they distribute to moist surfaces, as in the mouth cavity, though special end-organs, nerve components and central stations are differentiated for the more highly specialized chemical senses, taste and smell.
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Parker has shown that the general body surface of lower vertebrates is also sensitive to light. But the great physiological importance of distance receptors of this type has led to a concentration of this function in special areas of ectoderm, the optic pits, which were involved in the invagination of the neural tube and finally again evaginated as the optic cups in order to bring the retinal surfaces into a peripheral position more favorable for receiving the light rays. That the retina is a modified somatic sensory receptor is confirmed by Johnston's demonstration of the close anatomical relationship in lower vertebrates of its most primitive cerebral center, the tectum opticum, with the general cutaneous centers. An interesting side light is also shed upon this question by Whitman's demonstration in 1892 (Festschrift f. Leuckhart) that in certain leeches sensillse appear on each segment which in the caudal part of the body apparently function as organs of touch, but as we pass toward the head in successive segments, they become progressively modified in the direction of photoreceptors until in the head segments they are well formed eyes. Though this is probably a case of independent parallel differentiation, and is not ancestral to the vertebrate visual organs, it assists in the interpretation of the latter.
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68 C. JUD80N HERRICK
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The ganglia of unspecialized sensory components of the peripheral nerves m general, both visceral and somatic, are derived from the neural crests, i. e., from masses of ectoderm at the lateral borders of the neural tube at the line of its separation from the general ectoderm. That this neinral crest tissue is intermediate in type between the general ectoderm and the neural tube is shown by the fact already mentioned, that the ganglion cells of peripheral general cutaneous nerves are sometimes enclosed within the neural tube (the so-called giant cells of the spinal cord of some fishes) instead of lying in the usual position laterally of the spinal cord.
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Evidence is constantly accumulating that some if not all of the special sensory components have been derived from the unspecialized visceral and somatic sensory components. The history of the evolution of the lateral line and auditory systems from the unspecialized somatic sensory systems may be regarded as demonstrated from the fields of comparative anatomy, comparative physiologj'^ and comparative embryology. The history of the central diflferentiation of the lateral Une lobe and tuberculum acusticum from the somatic sensory colunm has been clearly demonstrated anatomically by Johnston; that the lateral line and auditory functions are closely related to the general tactile sense has been shown physiologically by Parker; and Landacre is able to illustrate in the embryological history of fishes an interesting relation between the neural crest and the dorso-lateral series of placodes in the origin of the lateralis and acoustic ganglia.
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A similar history is presented in the visceral sensory system, where the ganglia of the unspecialized visceral nerves come from the neural crest, while those of the specialized gustatory component come from a special system of cutaneous placodes.
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The olfactory nerve probably belongs to the last tjrpe, with this difference, that its peripheral neurones retain their positions in the placode instead of migrating inward to form a ganglion. There are, however, some elements which migrate from the olfactory placode to form a deep ganglion on the olfactory nerve, whose morphology is very obscure. Some of these migrating elements have been shown by Brookover in Amia to form sheath
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THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS 69
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nuclei of the olfactory fibers, others differentiate into the neurones of the ganglion of the nervus tenninalis. The character of the latter nerve and ganglion demands further investigation.
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Thus we find that each functional system of nerves has its peculiar type of development, peripheral end-organs, nerve components, ganglia and central connections, and for that the reflex arcs established among these fimctional systems constitute the most valuable imits of nervous structmre and function. Segmental and other gross subdivisions, which have the sanctions of long use and practical convenience, will of course continue to serve a useful purpose, but the fundamentally valuable data of neurology will more and more tend to be cast in the molds of these functional systems. This is true because in animal evolution the controlling fact has been the adjustment of the body to various environmental influences and the nervous system has been the medium of this adjustment.
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3. THE ORIGIN OF THE SENSORY COMPONENTS OF THE CRANIAL GANGLIA
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FRANCIS L. LANDACRE From Ohio State University, Columbue, Ohio
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WITH THREE FIGURES
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Professor Herrick has set before us clearly the principal conclusions derived from the attempt to analyze from a functional standpoint the cranial ancj spinal nerves, chiefly among the Ichthyopsida. The writer will confine himself to the inquiry as to what support these conclusions find in the development in a favorable tjrpe such as Ameiurus, laying emphasis largely upon the mode of origin and the morphological relations of the cranial ganglia, exclusive of the sympathetic ganglia. The ganglia in the vertebrates are the source of the central and peripheral fibers which have been grouped into the various component systems, and are in a very literal sense the foundation of these systems. Their mode of origin must affect vitally oiur conception of the theory of nerve components. The cat-fishes were chosen as a type, partly because the nerve components of the adult are known through Dr. Herrick's work, and partly because the character of the gustatory system is such that it seemed to be a favorable form in which to differentiate between the special visceral and general visceral systems of ganglia.
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In contrast with the favorable conditions offered by the embryo, the cranial nerves of the adult cat-fish are much more diflScult to analyze than those of such a form as Menidia, but by going back to a stage between eighty and ninety hours after fertilization, we find the ganglia in such a simple condition, with so little fusion of the various ganglionic components, that their analysis becomes comparatively easy. At this stage (as shown in fig. 1) we find
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72
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F. L. LANDACRE
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with one exception that the various ganglia are arranged exactly as in Menidia. The exception is found in the case of the 9th nerve, which contains a special somatic or lateralis ganglion which is absent in Menidia. The visceral system (in horizontal shading, Fig. 1) is not differentiated into a general and special visceral system, but is left as shown in Professor Herrick's chart of Menidia.^ We find here general somatic gangUa (unshaded in Fig. 1) in the
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Fig. 1. Reconstruction of the cranial ganglia of Ameiurus melas. Oc. 8, obj. 4mm, Spencer. Trigeminal, facial and anterior half of auditory from an embryo of 86 hours. The posterior half of the auditor3%the glossopharyngeal and the vagus from an embryo of 93 hours. General somatic ganglia imshaded; special somatic ganglia indicated by vertical shading; general and special visceral ganglia combined, indicated by horizontal shading.
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5th or gasserian, and in the 10th. Special somatic gangUa (in vertical shading, fig. 1) supplying the ear and lateral line organs, are found in the 7th, 8th, 9th and 10th. General and special visceral ganglia are found in the 7th or geniculate in the 9th and in four divisions of the 10th. The general and special visceral ganglia, as mentioned above, cannot be separated in any type in the adult, and even in a late stage of development cannot be distinguished.
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Starting with this type of ganglionic arrangement so conamon among the Ichthyopsida, let us inquire briefly how the various components are derived. In the region of the spinal cord, we have two components represented, the general somatic and the general visceral, both of whose ganglia are derived from the neural crest. In the head we have the general somatic and the general
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The cranial and first spinal nerves of Menidia. Jour, of Com. Neu., fig. 3, 1899
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COMPONENTS OF CRANIAL GANGLIA 73
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visceral components present also, and these are derived exclusively in Ameiurus, and probably in other types, from the neural crest, so that for these two fundamental systems the cranial ganglia and spinal cord ganglia fall into one category, as far as their mode of origin is concerned. This fact tends to emphasize in this respect the essential similarity of the head and cord region rather than the priority of one over the other. Whatever type of specialization the head region may have imdergone — and the specialized ganglia furnish the same kind of evidence as that furnished by other structures — the two regions are essentially alike in these two fimdamental systems, both of which are very old phylogenetically and quite generalized. We need not conclude, however, that because these two systems are old phylogenetically and generalized and are represented in both cranial and trunk regions, that they stand in any genetic relation to specialized systems of ganglia, such as the special somatic and special visceral ganglia of the head.
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In the discussion of the relation between general and special ganglia, the chief interest centers about the mode of origin of the special somatic and special visceral ganglia, which are peculiar to the cranial region and are not represented in the trunk.
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It wiU be easier to follow the origin of the special visceral or gustatory ganglia first. It has been known for a long time that certain of the cranial ganglia derived from the neural crest come into contact with the lateral epidermis in at least two regions. The more dorsal of these regions is at the level of the auditory vesicle, at which point the epidermal thickenings are known as dorso-lateral placodes; and the more ventral of these regions is at the level of the dorsal portion of the gill slit, where the epidermal l^ckenings are known as epibranchial placodes. The majority of observers, however, have expressed doubt as to whether the epidermis contributes cells to the neural crest portion of the ganglia.
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In Ameiurus, owing to the hypertrophied character of the gustatory ganglia and possibly to the precocious appearance of these ganglia, there can be no doubt that epibranchial placodes do contribute cells to the neural crest ganglia. These placodes are not mere contact points, but are true epidermal thickenings which
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74
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F. L. LANDACRE
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proliferate cells medially so that they are added in most cases en masse to the neural crest ganglia, and there is little cause for confusion as to their true nature. This mode of formation of the gustatory ganglia can be determined easily during the growth of the embryo in the case of the 7th and in the first two divisions of the 10th ganglia. The strongest confirmation comes, however, in the case of the epibranchial ganglion of the 9th nerv^e. In this nerve Professor Herrick can find only one t3^e of visceral fibers, the special or gustatory, and in the development of the 9th visceral ganglion the writer can find no trace of cells other than those that come from the placode, so . that one is warranted in concluding that the special visceral or gustatory ganglia come from the epibranchial placodes in Ameiurus. Every ganglion giving rise to gustatory fibers is derived in part from the placodes. This is true of the 7th, 9th, and four divisions of the 10th ganglia. (These are shown in cross-hatched shading in Fig. 2.) The fourth placode
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Fig. 2. Ganglia as in fig. 1, to show the origin of the special visceral components. General somatic ganglia unshaded; special somatic ganglia indicated by vertical shading; general visceral ganglia indicated by horizontal shading; special visceral ganglia indicated by cross-hatched shading.
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of the 10th ganglion had not appeared at the age at which this reconstruction wa's made. Further than this, the placodal derivative in each ganglion is in a general way proportionate to the number of gustatory fibers coming from the adult ganglion.
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The last two placodal derivatives of the 10th ganglion are quite small, and the last one answers quite accurately to many of the descriptions of the epibranchial placodes in the literature. The last placode of the 10th does not appear until after the neural
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COMPONENTS OF CRANIAL GANGLIA 75
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crest ganglion comes into contact with the skin, and is in fact indicated only by the presence of this contact. If it were not for the characteristic relation presented by the 9th nerve and the almost equally characteristic relation shown by the first two divisions of the 10th, one could easily accept for the last division of the 10th, the usual description in regard to the relation of the placodes to the neural crest cells, namely, that the neural crest comes into contact merely with the epidermis. But with the history of the 7th, 9th and the first two divisions of the 10th, we must conclude that the usual description answers to a condition where the gustatory component in a ganglion is small or late in appearance, as in the mammals and in man particularly, and that probably the placodal contribution to the ganglion is not suflSciently large or suflSciently well defined to be isolated, and does not appear before the contact is formed between the neural crest ganglion and the epidermis.
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We have then in Ameiurus evidence that the special and general visceral systems, which have been separated in the adult on the basis of the difference in the peripheral distribution and type of fibers, can be isolated in the embryo on the basis of mode of origin of the two types of ganglia. The special comes from the epibranchial placodes and the general from the neural crest. While this analysis of the ganglia cannot be made in the adult or even in a late stage of embryonic development, still the fact that they can be isolated in the earlier stages of their formation furnishes a striking confirmation of the analysis effected in the adult and tends materially to strengthen the point of view on which this analysis was made.
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Turning now to the other special system of the head, the special somatic or acustico-lateralis, we find a somewhat different history with a rather sharp distinction between the mode of origin of pre-auditory and post-auditory components of this system. The last one of the series, the lateralis 10th, is derived exclusively from a dorso-lateral placode which is a posterior extension of the auditory vesicle. It becomes detached from the epidermis much as the epi-branchial ganglia do and contains no neural crest cells. The next two in the series, the lateralis 9th and the auditory, seem to come exclusively from the auditory vesicle but ow
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76
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F. L. LANDACRE
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ing to the congestion of structures in the auditory region caused by the rapidly developing vesicle, it is difficult to be certain of their purely placodal origin. They may possibly contain neural crest cells in Ameiurus and have been described by other authors as arising largely from the neural crest. If they do contain neural crest cells, they represent a transition between the lateralis 10th, which is a pure placodal gangUon, and the condition to be described in the lateralis 7th ganglion. Passing anteriorly, we come to the first one of the series, or rather the first two, the lateralis ganglia associated with the geniculate ganglion of the 7th, which is
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Fig. 3. Ganglia as in figs. 1 and 2, shaded to show source of origin. Unshaded ganglia derived from neural crest; derivatives of dorso-lateral placodes indicated by vertical shading; derivatives of ventro-lateral placodes indicated by crosshatched shading.
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pre-auditory in position. These two ganglia are derived exclusively from the neural crest and are totally unlike the lateralis 10th in their mode of origin.
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We have thus as derivatives of the neural crest in the head all of the general visceral and general somatic gangUa of the 5th, 7th, 10th and the two special somatic ganglia associated with the geniculate ganghon of the 7th nerve. This is in rather striking contrast with the specific mode of origin of the special visceral ganglia, which are all derived from placodes, and at first glance seems to militate against the specific character of these gangUa as observed in the adult. But if one recall that the only condition imposed upon the nervous system, both peripheral and central, is that it shall furnish such correlations as will be profitable to the organism in adjusting it to its environment, it is not surprising
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COMPONENTS OF CRANIAL GANGLIA 77
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that sharp morphological distinctions should be rather frequently broken down. As illustrations of this, one has the dominance of certain centers in the brain as compared with the adjoining centers of similar characters: the usurpation by one nerve, of peripheral areas usually innervated by a totally different nerve and even by a different kind of component, or the dominating of a pure lateralis nerve such as the hyomandibular by components such as the general cutaneous and the visceral.
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From a functional point of view, there is nothing unusual in the double mode of origin of the special somatic or lateralis ganglia of the head. As Professor Herrick has pointed out, the whole ectoderm of the head, particularly the dorsal and the lateral portions, is to be considered as potentially nervous. This is evidenced by the formation of the neuro-epithelium of the olfactory organ, by the formation of the ganglia from the epibranchial placodes and the dorso-lateral placodes, and by the formation of the neural crest ganglia and even of the cord itself. All the diverse modes of ganglion formation seem to serve equally well in connecting the peripheral sense organs with the central nervous system.
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The olfactory neuro-epithelium, with, its sense cells acting as ganglion cells also, is evidently the simplest type of vertebrate ganglion. Next come the optic ganglionic cells which, while derived from the brain wall, still are only slightly removed from their epithelial origin. These ganghonic cells remain in the nervous layer and retain their position near their sense cells and do not migrate into the mesoderm. Following this, one has the auditory ganghon derived from the auditory pit but moving into the surroimding tissue and away from its sense cells. Its primitive character is evidenced by its bipolar ganglion cells and by the fact that its placode still remains a sense organ. Next, there is the lateralis ganglion of the 10th nerve, which comes from a placode but becomes entirely detached from it and hes in the mesoderm. In Ameiurus this placode, unlike the auditory placode, does not become a sense organ. It may possibly do so in other types, as Wilson maintains, and it would then resemble the auditory ganglion. Following this there are the epibranchial ganglia derived from
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78 F. L. LANDACRE
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placodes, concerning which there is no evidence in the ontogeny that these are sense organs at all. It seems probable, however, that in phylogeny they may have been derived from, or at least associated with, sense organs located at the dorsal portion of the gill slit, where the placodes now arise. If the epibranchial ganglia are included in this Ust tentatively, the whole class is characterized by the fact that they are associated more or less closely with special sense organs, which they afterward bring into contact with the brain, and thus serve to adjust the organism to its environment.
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The neural crest gangha stand in rather sharp contrast with this large class of ganglia, in that they are not associated in origin with any type of special sense organ and conserve the functions of general sensibiUty rather than the special senses, except in the case of the lateraUs 7th ganglia, so that they can hardly be placed in a series with the first class. If the lateralis 7th gangha were derived originally from the placodes in Ameiurus, as they seem to be in Cyclostomes, and have changed from a placodal type to a neural crest type, it is rather a process of usurpation than of evolution.
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The pre-auditory cranial region presents other modifications as compared with the post-auditory region fully as remarkable as this. The writer beUeves that the speciaUzed gangha should not be considered as derived from the unspeciahzed gangha in the sense that Johnston has shown the speciahzed centers of the brain to be derived from the unspeciahzed centers. These stand in a genetic relationship to each other. On the other hand, the placodal gangha have arisen in the potentially nervous ectoderm in response to the need of a more definite correlating apparatus and have come from the region of the sense organ. The neural crest ganglia have arisen in response to the same need, but have come from the region of the cord and brain. In the case of the preauditory laterahs gangha, the second type seems to have usurped the place and function of the first type and this may be going on even in the auditory and lateralis 9th. This change would be no more remarkable than other well known changes in the peripheral distribution and composition of nerves, which tend to adapt
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COMPONENTS OF CRANIAL GANGLIA 79
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the organism more accurately to its enviromnent, or to a different environment, or to integrate the activities of the organism itself. All of these changes, while presenting puzzling morphological conditions, tend to emphasize the idea that the functional needs of the organism rather than consistency in morphological detail is the key to the compUcated nervous mechanism of the vertebrates. The original characterization of a nerve component included the following distinctive points. The peripheral sense organs are of a common type with a common function. The fibers of a given component are usually of a definite size, thus enabling one to trace them through their ganglionic connections to the brain. The ganglia are definitely localized and sometimes in the most favorable types sharply isolated from the adjoining ganglia. The central ending of a given component is definitely localized. From the embryological evidence, we can add to this characterization the fact that the ganglionic components are definite in their mode of origin and except in the case of the preauditory lateralis ganglia are specific in their mode of origin. The general visceral and general somatic ganglionic components represented in both cranial and trunk regions are derived from the neural crest. The special visceral components are derived from the epibranchial placodes. The special somatic components show a transition from a pure placodal type in the lateralis 10th through a possible intermediate type in the lateralis 9th and auditory, to the pure neural crest type in the lateralis 7th.
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4. THE PROBLEM OF THE CORRELATION MECHANISMS
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JOHN B. JOHNSTON
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University of Minnesota WITH ONE FIGURE
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The next general problem before the anatomist of the nervous system is that of the correlation mechanisms. The organization of the primary receptive and effective mechanisms has found adequate expression in the doctrine of the functional divisions of the nervous system. The validity and the usefulness of this doctrine are demonstrated by its adoption by an increasing number of workers in this coimtry and abroad. The task of elaborating a complete functional morphology of the nervous system, however, has only been begim by the theory of fimctional divisions.
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The problem of the correlating mechanisms is as many-sided and complex as the nervous system itself, as broad and varied as the whole of human life. The problem involves (1) all those questions relating to the structure and connections of the individual neurones, the character of the nerve impulse and the mode of its propagation through the neurone and from one neurone to another; continuity, synapses, stimulus threshold, summation, inhibition, etc.; and (2) all those questions r^arding the means by which simple reflexes are combined into larger actions directed for the welfare of the organism as a whole.
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It is to the solution of the second set of problems that comparative neurology can contribute most at the present time. The problem is fundamentally more than all else a problem in the genesis of structures functioning in an adaptive manner. Structure and function can not be separated and both must be studied in the Ught of their purpose. Structures in action — actions performed by definite structures — have for their end the adaptation of the organism to the conditions of its Uf e. The way in which the parts
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82 J. B. JOHNSTON
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of the nervous system work together m directing the various organs for the welfare of the organism as a whole is the chief guide in the interpretation of the nervous system. This has been the burden of the teaching of the functional morphologist. But to discover how the parts of the nervous system work together it is necessary to inquire how the nervous mechanisms have come to be what they are through the process of evolution of the race. What were the first or simplest structures serving certain functions? How were they modified and speciahzed? What causes led to the increasing complexity of their structure? By what steps have they come to be what they are? In this way alone can we discover fully what they are and what they mean. For this way of looking at the nervous system we may use the name genetic method. It is in attacking the most complex problem that a complete genetic method is most needed. The study of the correlating mechanisms, to repeat, is a study of the evolution of nervous structures functioning in such a way as to secure the adaptation of the organisms concerned.
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How have simple reflexes been combined into adaptive actionsystems? What are the impulse pathways by means of which one simple reflex is combined with others into a larger whole, while certain others are left passively idle and still others are actively shut out from participation because antagonistic to the main purpose? Nearly everyone of our common actions answers to this description, and those actions have grown up through a long past by the combination of simpler elements. We see this in the growth of the infant, in his learning to see things, to grasp objects, to walk, to talk; and we can more or less fully trace the phylogenetic history of some of our actions. The most direct and effective method of attack is to study the genesis of the actions themselves and the parallel genesis of the nervous mechanisms concerned in them. An excellent example of the right mode of approaching these problems is the study of the genesis of movements in amphibian tadpoles presented to this Association at its last meeting by Professor Coghill.
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Among the many phenomena requiring explanation, the spread of reflexes to distant segments and the cooperation of distant seg
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THE PROBLEM OF THE CORRELATION MECHANISMS 83
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ments in a single action will illustrate the point of view here suggested. Perhaps the most constant result in experiments upon animals is the tendency for the responses to be complete or partial reproductions of habitual or common acts. In the highly specialized reflexes of the dog certain kinds of stimulation produce definite movements. For example, stimulation of the shoulder in any of several ways calls forth the scratch-reflex. It is frequently noticed, when the limbs are called into action by a stimulus, that the form of their movement is dominated by the method of progression characteristic of the given animal. Thus in the dog various forms of excitation produce attitudes of the limbs which are due to the dominance of the trotting gait in this animal. If the stimulation be at a hind foot the movement of the fore leg or legs is that which would form part of the act of trotting. If painful stimulation of one hind foot in the spinal dog be continued the flexor muscles of that leg contract and the other three legs move in the rhythm of progression, that is, the hurt foot is held up and the other three feet run away (Sherrington, Integrative Action, p. 240). So, in experiments on lower vertebrates in which general somatic nerves are stimulated, the responses are movements of swimming. Witness the recent work of Sheldon on chemical stimulation of the dogfish. If the stimulation is strong enough it calls forth contraction of muscles of distant segments, perhaps of all segments of the body. In this spread of reflexes to distant segments we have one of the fundamental elements in the combination of reflexes.
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The responses called forth by irradiation to distant segments through the spinal cord are not hap-hazard, but are parts of typical actions. The phenomena of irradiation must therefore rest upon systems of nerve paths produced in the course of the evolution of characteristic behavior of the given species. Long spinal irradiation is but a specific illustration of what we may call segmental, or metameric correlation.
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When we look for the mechanism of this segmental correlation, we find a plethora of materials and our diflSculty is to sift out definite structures and discover their specific functions. In the spinal cord and brain of vertebrates we recognize in each of the
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84 J. B. JOHNSTON
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receptive columns, somatic and visceral, primary receptive neurones and other neurones {substantia reticularis) which constitute the structural means for correlation. Fibers arise from the somatic receptive colunm — the dorsal horn — to go to other segments to end in the same column on the same or opposite side. Other fibers go to the somatic motor column of one or more segments. These latter may serve to call into action larger masses of muscle, but can have only a low value in correlation.
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Those neurones by which the in-coming impulses are spread to distant segments of the same column are of especial significance in correlation. Two chief sets of such neurones are recognized. The fibers of one of these run up or down the cord in proximity to the dorsal horn itself into which the fibers turn after a longer or shorter course. The second set of neurones send their fibers by way of the ventral decussation of the cord to end in the dorsal horn of the opposite side in a higher or lower segment.
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Whatever may be the specific mode of functioning of the correlation neurones within the spinal cord, numerous long fibers of both sets of neurones have played an important part in the evolution of the brain. Homolateral fibers from the dorsal horn of the cord reach the cerebellum and many more join these from the nuclei cuneatus and gracilis of the medulla oblongata. These direct cerebellar fibers are joined also by external arcuates from the other side of the medulla oblongata. Crossed fibers from the dorsal horn of the cord together with many more from the nuclei in the oblongata, including the centers for the fifth and eighth nerves, and still others from the dentate nucleus of the cerebellum, form a great system or several systems of fibers, of which the medial lemniscus is the type. The fibers of both direct and crossed systems pass from the somatic sensory column of lower segments to the same column in higher segments. These are fundamentally segmental correlation fibers, but their great numbers and their definite arrangement with reference to certain segments and nuclei in the brain are due to a special significance which they have obtained in consequence of the development of special sense organs.
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It is customary to speak of the development of organs of special sense in the head as the cause of the development of the brain.
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THE PROBLEM OF THE CORRELATION MECHANISMS 85
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Hum
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n term .
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e>a.
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SCHEMA OF SBQMBNTAL CORRBLATINQ TRACTS
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On the left are shown some of the long ascending tracts concerned in somatic receptive fimctions in man. On the right is shown the segmented brain of a hypothetical primitive or ancestral form in which the evagination of the forebrain and the retinal areas has begun. Otherwise the brain is simply the anterior portion of the neural tube. In the arrangement of the direct and crossed correlating fibers the specialized tracts of true vertebrates are foreshadowed. The place of ending of the nervus terminalis in this figure is the primordial somatic cortex.
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86 J. B. JOHNSTON
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This is true, but we are too apt to lose sight of the importance of the correlation of general somatic sense organs with the special sense organs. The primary receptive centers for the eye, ear and nose account for only a small part of the increased size of the anterior part of the neural tube. The greater part of the enlargement called the brain is due to the material serving for correlation between eye, ear, and nose and between those and the skin and muscles of the body.
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The mechanism for correlation of the general bodily organs with the organs of special sense was ready-prepared before those sense organs made their appearance in the vertebrate ancestors. The ancestral forms had no head, only an anterior end. What is now head was in those ancestors a region with a complete series of segments and sensory nerves. We have no evidence of somatic motor nerves further forward than the present oculomotorius. Two forms of sensory neurones were present : one which we may call the ganglion-cell type, sensitive especially to mechanical stimuli, with chemical, photic and thermal sensitiveness in the background; the other which came to form the olfactory organ, with chemicar sensitiveness dominant. Both these had been derived perhaps from a single still more ancient and unspecialized type of peripheral sense cells. The speciaUzation of the sense cells in the anterior segment of the body as cells of chemical sense and their collection into a restricted area gave rise to the first special sense organ, the olfactory. The sense cells of the rest of the body likewise collected into a long strip at either side of the neural plate and gave rise to the spinal and cranial ganglia. In this simple animal the chief long paths in the nervous system were concerned with segmental correlation and these paths form the basis for the high development of correlation mechanisms, which is the chief characteristic of vertebrate animals and which enabled this phylum, by adapting itself to wider and wider ranges of environmental conditions, to become the dominant race of animals.
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A certain part of the ganglion-cell type of sensorj'^ neurones, especially in the anterior end of the body, from the first tended to specialize in the direction of light percipient cells and in three or more segments of the head these cells became aggregated into eyes.
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THE PROBLEM OF THE CORRELATION MECHANISMS 87
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These formed parts of the bram wall and became evaginated, as is well known. I have several times brought forward evidence that the eyes were developed from the general somatic receptive column and I have suggested that the optic tract fibers constituted essentially a correlation tract comparable to the lemniscus. The most important result following from these facts is now to be*pointed out, namely, that this optic tract entered the somatic sensory column where its impulses came at once into relation with impulses from the skin and muscles, brought up by the long tracts for the sake, originally, of segmental correlation. Thus early the primordial structiu-es were present which provided against the dominance of direct and unmodified reflexes, such as obtains in invertebrates, and provided for the control of body movements by the cooperation of two or more sensory mechanisms taking account of different factors in the environment. This it is which distinguishes all vertebrates from invertebrate forms, — the degree to which the power to guide their actions with reference to impulses of two or more kinds is developed.
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When later, the acustico-lateralis system of sense organs arose to take account of slow wave-stimulation and developed into an organ of the static sense, and still later gave rise to an organ of hearing, these organs sent their impulses into the same somatic sensory column, whose long tracts served also for correlation of these with the skin and muscles.
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It was in this way that the brain came to be developed as a great collection of correlation centers. The gray matter in the tectum and the thalamus, as soon as the eye was formed, served at once, not as optic centers alone, but as somatic-optic correlation centers. It is noticeable that the fishes which present well formed optic centers in the thalamus are not alone those with large eyes but the strong-swimming, active forms. For example, among ganoids the active and predacious freshwater dogfish (Amia) has a well developed lateral geniculate body, while the sluggish bottom-feeding sturgeon has not.
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Again, the gray matter in the segments following the tectum became a center for the correlation of canal-organ impulses with those of the muscle sense in the control of muscular move
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88 J. B. JOHNSTON
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ments. Here was developed the most sharply specialized and highly characteristic region of the vertebrate brain, the cerebellum, Deiter's nucleus and area acustica serving as a static mechanism, an organ for muscle tone, etc. The great importance to this mechanism of the sensory impressions from the muscles and the skin which ate carried up by the dorsal tracts and restif orm bodies, has been so often pointed out that we need not dwell on it here.
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Further, the common and primitive basis of correlation tracts which put these sense organs into relation with the muscles and skin, served also to put them into relation with one another. This must be passed over for the sake of discussing briefly the conditions determining the development of the somatic cortical centers in which correlation of all these sense surfaces is brought about, and apparently on a higher plane.
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The cerebral cortex consists essentially of two parts, a visceral cortex and a somatic cortex. The former will be discussed in another paper. Here let us examine briefly the conditions for the development of the somatic cortex. In the more active lower vertebrates the optic-somatic correlation centers play so important a part in the more intelligent seeming activities that some one has said that the tectum plays the part of cortex for the fish. Why have not some of the lower correlation centers, say the optic, developed into the cortex? Chiefly for the reason that the presence of the special sense organ demands the use of the greater part of the substantia reticularis in those centers for the direction of simple or combined reflexes in which the impulses from one sense organ play a dominant rdle. It is characteristic of cerebral cortex that it is free from the domination of any one kind of sensory impulses. Since there is some limit to the development of any correlation center — at least the Umit of the power of growth with which that part of the nervous system is endowed in the embryo — a center which is largely concerned with any one sense could not well supply the material for cortical functions.
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An influence favoring the development of cortical centers in the telencephalon is the presence of the olfactory centers in that segment. The olfactory organ is not only a special organ of the chemical sense of ancient standing, but it has acquired special
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THE PROBLEM OF THE CORRELATION MECHANISMS 89
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importance by reason of its power to function at a distance. As pointed out by Sherrington, the olfactory organ is a distance receptor in the search for food. It is important, therefore, that the olfactory organ be correlated with the visual organ and with the muscles which are chiefly concerned in the capture of food. WTiere is this correlation provided for? In part at least in the olfactory centers in the hypothalamus and epithalamus and the optic centers with which these are inter-connected. Indeed, these socalled olfactory centers in the diencephalon are in reaUty the meeting-places or clearing-houses for impulses of different sorts and should be called olfacto-gustatory, olfacto-visual and olfactomuscular correlation centers. I see no reason why these centers should not have suflSced for the combination of all sorts of reflexes in which the olfactory organ was concerned as a distance receptor in the search for food. The most that we can say as to the influence of the olfactory organ is that an olfactory-somatic correlation center in the telencephalon would perhaps have some advantage in eflSciency. The presence of the olfactory organ does not give any cley as to how such a center in the telencephalon came to arise. -^
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For this we must turn to the principle of metameric correlation. The long correlation tracts are believed to be more fundamental and of earlier origin than the special sense organs or the brain itself, and if such tracts reached the first brain segment regardless of the olfactory organ, then the development of an olfacto-somatic correlation center in the telencephalon is merely a question of its usefulness to the organism. Was there present in the first segment of the neural tube of vertebrate ancestors a segment of the somatic sensory colunm? Was this connected with lower segments of the same colunm by metameric correlation tracts? And could such a center offer the material and the conditions for the development of the somatic cortex? I believe all these questions are to be answered in the aflirmative.
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There is connected with the forebrain in selachians a nerve, evidently vestigeal, which bears a ganglion and is distributed to the epitheUum of the nasal sac. I believe that this represents the general cutaneous nerve component of this segment. The nerve
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90 J. B. JOHNSTON
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enters a part of the forebrain which in selachians receives fiber tracts from lower segments of the somatic sensory column, namely, the lenmiscus center in the thalamus and perhaps other centers. Here are evidences of the existence of a primary somatic sensory center and of correlatmg tracts in one of the lower groups of fishes. That ancestral vertebrates possessed a cutaneous nerve in the first segment and that its center was connected by long tracts with lower centers of the same sort is a reasonable deduction from this evidence and also is a priori very probable.
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Such a center was very favorably placed for the development of somatic cortex for two chief reasons. First, it had the advantage of proximity to the olfactory centers and the olfacto-gustatory cortex. Second, the correlating material of this segment of the somatic sensory column was the only one to be set free from the dominance of a special sense organ ; eye, ear, skin, or muscles. The N. terminalis disappeared and the cutaneous surface which it suppUed was invaded by the trigeminus. The substantia reticularis of the forebrain center, was then released from the work of combination of simple reflexes and came to serve for correlations of a higher order. This is a special case of a general tendency in the brain which has long been recognized, namely, the tendency toward segregation and condensation of centers for special functions. The cutaneous innervation of the head, originally provided by some ten or eleven segmental nerves, is in man almost all provided by the trigeminus with some branches from the first and second spinal nerves, and its center is condensed into the medulla oblongata. The special sense organs were restricted to one or a few segments from the first and have dominated those segments, as we have seen. The forebrain segment of the somatic colunm, while losing its primary sensory function, offered the opportunity for olfacto-somatic correlation and for the inter-correlation of somatic organs which sent impulses up to it over the long tracts. It can not be thought that the occasion or impulse for the development of this correlating center after it was freed from its primary sensory function was suppUed by the olfactory organ and centers alone. Olfacto-somatic correlation in the forebrain is to be regarded rather as incidental. Had there been no other occasion
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THE PROBLEM OF THE CORRELATION MECHANISMS 91
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for a somatic center in the forebrain, olfacto-somatic correlation would all have been cared for in the diencephalon. The cerebral cortex serves for correlation between tactile, muscular, static, auditory and visual impulses in a thousand ways in which olfactory impulses are not at all concerned. For the development of these somatic correlating functions the olfactory apparatus could have been neither the stimulus nor the directing force. If there had been no somatic sensory center in the forebrain, the somatic cortical functions would never have been located in the telencephalon. The determining factors in the development of the somatic cortex were: (1) the center for the nervus terminalis with the substantia reticularis belonging to it; (2) the fimdamental correlation tracts bringing up tactile, musculo-sensory and visual impulses to this center; (3) the reduction of the nerve which left the substantia reticularis free to serve for correlation of the impulses just mentioned; (4) and the advantage of a center where impulses of different kinds might interact upon equal terms. In this last, which seems at first a vague and intangible principle, lies the very essence of the conditions for the development of the higher cortical functions, memory, judgment, reasoning and the aesthetic faculties. Consciousness springs, as I believe, from the tension of indecision between two or more sets of impulses, any one of which coining alone would be followed by a simple reflex; or between two or more possible responses to a stimulus. If so, we can not expect a very high grade of consciousness in animals in whose nervous systems each center is under the dominant influence of one sense organ. The tension in the olfacto-visual, olfacto-gustatory, or visuo-muscular correlation centers would, too often, be dissolved by the dominant influence of one or other sense organ. Inhibition would not be very prolonged, one set of conditions would not hold the attention long for the purpose of weighing the difi'erent impulses or responses over against one another. The solution of the tension through a simple reflex or a combination of reflexes of a low order or of a habitual type would be unfavorable to the development of memory, of adaptability in responses, or of deliberation, which is essential to intelligent action.
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92 J. B. JOHNSTON
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In the forebrain center, however, just those conditions are presented which are favorable to the development of the faculties of intelligence. In addition to the freedom from the unequal influence of one set of impulses, the fact that impulses reach this center only by long paths and usually by a relay of three neurones is of great importance. In the definition of cortex in general I have elsewhere given weight to the relay of three neurones for these reasons: (1) Such a relay removes the cortex farther from the realm of direct reflexes by increasing the time of reaction through the cortex. The cortex is never involved where extraordinarily quick response is necessary. (2) The relay restricts the number of impulses passing to the cortex. Impulses to reach the cortex either must have suflBcient energy to connnand the right of way (through the synapses) or they must find the way prepared for them through attention; and attention itself is a conscious process and one of the greatest factors in the further development of consciousness.
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If we were to look at the visceral sensory mechanisms we should find essentially the same arrangements as have been described for the somatic: a longitudinal colunm with long tracts connecting distant segments with one another. Into this column came the fibers of taste and smell and the long tracts brought these into relation in the forebrain, so giving rise to the visceral cortex.
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I present, then, as three matters of great importance in the study of the correlation mechanisms: (1) the fundamental chai'acter of metameric correlation; (2) the development of the brain through the local hypertrophy of this segmental mechanism under the influence of the special sense organs, and the related segregation of special centers, and (3) the indifference of the somatic correlation center in the telencephalon, which offers the essential condition for the development of the cerebral cortex as the organ of conscious life.
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PROCEEDINGS OF THE AMERICAN ASSOCIATION OF ANATOMISTS
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TWENTY-FIFTH SESSION
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In the Embryological Laboratory, Harvard Medical School, Boston, Massachusetts, December 28, 29, and SO, 1909.
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Tuesday, December 28, 9.30 a. m., to 1.00 p. m.
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The twenty-fifth session was called to order at 9.30 am. by President, James Playfair McMurrich, who appointed the following conmiittees.
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Committee on Nominations; Charles S. Minot, Chairman; Thomas G. Lee, Simon H. Gage.
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Avditing Committee; Milton J. Greenman, Chairman; August G. Pohlman.
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Symposium of Comparative Neurology:
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George H. Parker, Harvard University. The phylogenetic origin of the nervous system.
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C. Jfdson Herrick, Xjniversity of Chicago. The relations of the peripheral and central nervous systems in phylogeny.
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Francis L. Landacre, Ohio State iJniversity. The origin of the sensory components of the cranial ganglia.
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John B. Johnston, University of Minnesota. The problem of correlation certers and the evolution of the cerebral cortex.
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The general discussion was opened by Henry H. Donaldson, Wistar Institute of Anatomy.
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The remainder of this session was devoted to the presentation of the following neurological papers:
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Stewart Paton, Princeton y New Jersey. Neurofibrillation in relation to the first
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movements of vertebrate embryos. Susanna Phelps Gage, Ithaca, New York. A pair of dorsal cerebral sacs on
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either side of the terma in a 35 day and other human embryos, comparable
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with the cerebral sacs in fishes. S. Walter Ranson, Northwestern University Medical School. Non-medullated
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nerve fibers in the spinal nerves.
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94 AMERICAN ASSOCIATION OF ANATOMISTS
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Henry H. Donaldson, Wistar Institute of Anatomy. On the percentage of water in the central nervous system of the albino rat. (Lantern slides.)
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S. Hatai, Wistar Institute of Anatomy. Preliminary report on the inheritance of the weight of the central nervous system in rats.
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John B. Johnston, University of Minnesota. Early stages in the evolution of the cerebral cortex. (Only an abstract presented.)
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The following neurological papers announced were read by title:
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C. JuDSON Herrick, University of Chicago. The analysis of the paraterminal body and its relation to the hippocampus in lower brains.
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Burt G. Wilder, Cornell University. The weight and form of the brain of some American negroes; illustrated by specimens, photographs and charts.
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Elizabeth H. Dunn, University of Chicago. Some findings regarding the distribution of splitting medullated nerve fibers in the peripheral nervous system.
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Tuesday, December 28, 2 to 5 P. M. Demonstrations as follows:
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Charles R. Essick, Johns Hopkins University, (a) Specimens showing the development of the arcuate nuclei in the human embryo; (6) Dissections to show migration of cells in the medulla of the pig embrvo.
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Susanna Phelps Gage, Ithaca, New York. Models of the head of a five-weeks human embryo.
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Clarence M. Jackson, University of Missouri. Models of the thoracic and abdominal viscera of the human embryo.
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John B. Johnston, University of Minnesota. Models illustrating the cortical areas in fishes and amphibians.
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Frederick T. Lewis, Harvard Medical School, (a) The first Ijonph glands in rabbit and human embryos. Specimens and models illustrating tae relation of the atrioventricular valves to the interventricular foramen.
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Stewart Paton, Princeton^ New Jersey. Preparations showing neurofibrillation in relation to the first movements of the vertebrate embryo.
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William S. Miller, University of Wisconsin. Reconstruction models showing the arrangement of the cartilages in the trachea and bronchi of the Guinea pig. (6) Arrangement of the muscle in the trachea and at the carina tracheae in various animals.
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S. Walter Ranson, Northwestern University Medical School. Sections of the human sciatic nerve showing non-medullated nerve fibers.
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Florence R. Sarin, Johns Hopkins University. Specimens showing the development of the structural unit in the embryo pig's spleen.
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J. Parsons Schaepfer, Cornell University Medical School, (Ithaca, New York). Modelft showing the development of the lateral wall of tne nasal cavitv iii man.
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Harold D. Senior, College of medicine, Syracuse University. A method of obtaining orientation points in serial sections, for use in plastic reconstructions.
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Charles F. Silvester, Princeton University. Preparations showing the presence of permanent lymphatico-venous communications at the renal level in the South Araierican monkey.
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George L; Streeter, University of Michigan. Demonstrating for (a) F. H. Busby. Models showing the topography of the cerebral cortex of the opossum. (6) J. H. Stokes. Two models, showing the facial, vestibular and cochlear nerves with their central connections in the opossum.
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(c) H. A. Calhoun. Models of the medulla oblongata of the opossum.
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(d) H. W. Stiles. Model showing the Ventricular system of the brain of the opossum.
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(e) H. N. T. Nichols. Double spinal ganglia.
 +
 +
John L. Bremer, Harvard Medical School. Demonstration of unit room No. 203, showing equipment and material used in the first year's course in Embryology and Histology in the Harvard Medical SchooL
 +
 +
 +
PROCEEDINGS 95
 +
 +
Members of the staff demonstrated models illustrating vertebrate development; made by students in the Harvard Laboratory of Comparative Anatomy.
 +
 +
Wednesday, December 29, 9.30 a. m. to 1 p. m. Session for
 +
 +
THE reading of PAPERS, FlRST ViCE-PrESIDENT WiLLIAM S.
 +
 +
Miller and President James Playfair McMurrich, presiding.
 +
 +
Elexious T. Bell. University of Missouri. On the staining of fat in muscle fibers.
 +
 +
Victor E. Emmel, Washington University Medical School. Observations on the differentiation of regenerating epidermal and striated muscle tissue in the lobster.
 +
 +
Arthur E. Hertzler, Kansas City, Missouri. The formation of fibrous tissue.
 +
 +
George S. Huntington, Columbia University (New York City). The development of the thoracic ducts in embryo of the cat (with lantern slides).
 +
 +
Edwin G. Conklin, Princeton University. Cell size and nuclear size.
 +
 +
Jeremiah G. Ferguson, Cornell University Medical School (New York City), 1. The hypobranchial arterial system in the Selachiae. 2. The thyroid gland of elasmobranchs, with special reference to its Vascular supply.
 +
 +
Clarence M. Jackson, University of Missouri. Electric heating for laboratory apparatus.
 +
 +
The following papers announced on the program were read by title:
 +
 +
Charles S. Mi not, Harvard University. Notes on an early stage of pregnancy.
 +
 +
Herbert M. Evans, Johns Hopkins University. Note on the development of the superficial arteries of the nead in the human embryo; especially the occipitalis, auricularis posterior and temporalis superficialis.
 +
 +
Harvey E. Jordan, University of Virginia. A further study of the human umbilical vesicle.
 +
 +
William F. Mercer, Ohio University. Development of the metacarpal bones in the leg of the sheep.
 +
 +
12 to 1. Address by Professor Doctor Franz Weidenreich of Strassburg, Germany, On the morphology of the blood cells and their relation to each other. (Die Morphologie der Blutzellefi und ihre Beziehungen zu einander.)
 +
 +
This address, given at the invitation of Professor Minot and the Executive Committee, was delivered in German. At its conclusion, the Association extended Professor Weidenreich a vote of thanks and appreciation.
 +
 +
Wednesday, December 29, 2 to 4 p. m. Demonstrations AS follows:
 +
 +
Elexious T. Bell, University of Missouri. Preparation showing fat in muscle
 +
 +
fibers. Victor E. Emmel, Washington University Medical School. Preparations showing
 +
 +
the differentiation of regenerating epidermal and striated muscle tissue in the
 +
 +
lobster.
 +
 +
 +
96 AMERICAN ASSOCIATION OF ANATOMISTS
 +
 +
Jeremiah S. Febguson, Cornell University Medical School (New York City), (a) Dissection of the hypobranchiai system of the dogfish. (6) Sections and total mounts of the thyroid gland of elasmobranchs.
 +
 +
George S. Huntington, Columbia University and C. F. W. McClure, Princeton University. Models illustrating the development of the jugular lymph sacs in mammalia.
 +
 +
Arthur E. Hertzler, Kansas City Missouri. Pieparations and drawings showing the formation of fibi ous tissue.
 +
 +
Professor Doctor Weidenreich. — A demonstiation of a seiies of pieparations showing the morphology of the blood cells and their relation to each other.
 +
 +
Wednesday, December 29, 4 p. m. Business Meeting.
 +
 +
On motion, the minutes of the Secretary as published in the Anatomical Record, Vol. Ill, No. 1, page 62 to 74, were approved. The Treasurer made the following report for the year 1909:
 +
 +
Total receipts for the year 1909 S1381 .20
 +
 +
Balance on hand December 24, 1908 172 . 17
 +
 +
Total $1553.37 $1553.37
 +
 +
Expenses of the Secretary. Baltimoie meeting $32.40
 +
 +
Smoker, Johns Hopkins Club 7 .60
 +
 +
Postage and envelopes 26.20
 +
 +
Wistar Insi itute of Anatom> for 275 subscriptions to American Journal of Anatomy and Anatomical Record at
 +
 +
$4.50 1237.50
 +
 +
Printing 19.40
 +
 +
Total $1323.10 1323.10
 +
 +
 +
 +
Balance on hand December 23, 1909, deposited in the Farmers and Mechanics Bank, Ann Arbor, Michigan $230. 27
 +
 +
August G. Pohlman reported for the Auditing Committee: We have examined the accounts of G. Carl Huber, SecretaryTreasurer for the year 1909 and found them correct."
 +
 +
On motion the reports of the Treasurer and of the Auditing Committee were accepted and adopted.
 +
 +
James Playfair McMurrich and Ross G. Harrison, members from this Association of the International Committee on Reformation of Myological nomenclature, reported progress. The committee was continued.
 +
 +
The Committee of this Association, consisting of Charles S. Minot, Franklin P. Mall, James Playfair McMurrich, G. Carl Huber, George A. Piersol, George S. Huntington, in charge of arrangements for the International Congress of Anatomy to be
 +
 +
 +
PROCEEDINGS 97
 +
 +
held in Brussels, August 7 to 11, 1910, through its Chairman, Dr. Minot, reported progress.
 +
 +
The following were recommended by the Executive Committee for election to membership in the Association.
 +
 +
Robert P. Bigelow, Ph.D., Instructor in Biology and Librarian, Massachusetts
 +
 +
Institute of Technology. David Cheever, A.B., M.D., Demonstrator of Anatomy, Harvard Medical School, H. K. Corning, M.D., Professor of Anatomy, Basely Switzerland. Victor E. Emmel, Ph.D., Instructor in Histology and Embryology, Wc^hington
 +
 +
University^ St. Louis. Frederick Etherington, M.D., Professor of Anatomy, Queen* s University^ Kingston, Canada. William S. Halsted, M.D., Professor of Surgery, Johns Hopkins University. Davenport Hooker, M.A., Instructor in Anatomy, Medical Department, Yale
 +
 +
University. Franklin P. Johnston, A.B., Austin Teaching Fellow, Harvard Medical School. 3. F. McClendon, Ph.D., Assistant in Histology, Cornell University Medical
 +
 +
School, New York. Max Morse, Ph.D., Instructoi in Biology, College of the City of New York. Ernest Sachs, A.B., M.D., Physician and Surgeon, New York City. Daniel M. Shoemaker, B.S., M.D., Associate Professor of Anatomy, St. Ijouis
 +
 +
University. James M. Stotsenburg, M.D., Curator and Junior Associate in Anatomy,
 +
 +
Wistar Institute. Frederick Tilney, A.B., M.D., Associate in Anatomy, Columbia University,
 +
 +
New York City. I^ouis Hill Weed, A.M., Johns Hopkins Medical School. Baltimore. Franz Weidbnreich, M.D., a.o., Protessor and Prosector of Anatomy, Strass hurg, Germany.
 +
 +
On motion, the Secretary was instructed to cast a ballot for election to membership in the American Association of Anatomists of applicants recommended by the Executive Committee. Carried.
 +
 +
The Association then proceeded to the consideration of the constitution placed before this Association at its last meeting by the committee on revision of the constitution, consisting of G. Carl Huber (Chairman), Henry H. Donaldson and Robert R. Bensley, and sent to each member at least one month in advance of this meeting as provided for in Section 2, Article VII, of the constitution.
 +
 +
On motion, the constitution proposed by the committee was considered article for article. Each article was voted on separately and adopted as proposed or as amended. In conclusion the entire constitution was unanimously adopted as a whole, in the following form:
 +
 +
 +
98 AMERICAN ASSOCIATION OF ANATOMISTS
 +
 +
CONSTITUTION.
 +
 +
ARTICLE I
 +
 +
Section 1. The name of the Society shall be "The American Association of Anatomists.
 +
 +
Sec. 2. The purpose of the Association shall be the advancement of anatomical science.
 +
 +
ARTICLE n
 +
 +
The officers of the Association shall consist of a President, a Vice-President, and a Secretary, who shall also act as Treasurer. The President and the Vice-President shall be elected for two years, the Secretary for four years. In case of absence of the President and Vice-President, the senior member of the Executive Committee shall preside. The election of all the officers shall be by ballot.
 +
 +
ARTICLE III
 +
 +
The management of the affairs of the Association shall be delegated to an Executive Committee, consisting of eleven members, including the officers. Two members of the Executive Committee shall be elected annually, and, so far as possible, election of members of the Executive Conmiittee shall be in proportion to the geographical distribution of members. Five shall constitute a quorum of the Executive Committee.
 +
 +
ARTICLE IV
 +
 +
The Association shall meet at least annually, the time and place to be determined by the Executive Committee. The annual meeting for the election of officers shall be the meeting of convocation week, or in case this is not held, the first meeting after the new year.
 +
 +
ARTICLE V
 +
 +
Section 1. Candidates for membership must be persons engaged in the investigation of anatomical or cognate sciences,
 +
 +
 +
PROCEEDINGS 99
 +
 +
and shall be proposed in writing to the Executive Conunittee by two members, who shall accompany the recommendations by a list of the candidate's publications, together with references. Their election by the Executive Committee, to be effective, shall be ratified by the Association in open meeting.
 +
 +
Sec. 2. Honorary members may be elected from those who have distinguished themselves in anatomical research. Nominations by the Executive Conmiittee must be unanimous and their proposal with a reason for recommendations shall be presented to the Association at an annual meeting, a three-fourths vote of members present being necessary for an election.
 +
 +
ARTICLE VI.
 +
 +
The annual dues shall be five dollars. A member in arrears for dues for two years shall be dropped by the Secretary at the next meeting of the Association, but may be reinstated at the discretion of the Executive Committee on payment of arrears.
 +
 +
ARTICLE VII.
 +
 +
Section 1. Twenty members shall constitute a quorum for the transaction of business.
 +
 +
Sec. 2. Any change in the constitution of the Association must be presented in writing at one annual meeting in order to receive consideration and be acted upon at the next annual meeting; due notice of the proposed change to be sent to each member at least one month in advance of the meeting at which such action is to be taken.
 +
 +
Sec. 3. The ruling of the Chairman shall be in accordance with ^'Robert's Rules of Order.
 +
 +
The orders adopted by this Association, which read as follows, were not altered :
 +
 +
Newlv elected members must qualify by pajrment of dues for one year within thirty days after election.
 +
 +
The maximum limit of time for the reading of papers shall be twenty minutes.
 +
 +
The Secretary and Treasurer shall be allowed his tiaveling expenses and the sum of $10 toward the payment of his hotel bill, at each session of the Association.
 +
 +
That^ihe Association discontinue the separate publication of its proceedings and that the Anatomical Record be sent to each member of the Association, on payment of nis annual dues, this journal to publish the proceedings of the Association.
 +
 +
 +
100 AMERICAN ASSOCIATION OP ANATOMISTS
 +
 +
Charles S. Minot, as Chairman of the Committee on nominations, placed before the Association the following nominations:
 +
 +
President George A. Piersol.
 +
 +
Vice-President, Charles F. W. McClure.
 +
 +
Secretary 'Treasurer, • G. Carl Huber.
 +
 +
For Members of the Executive Committee.
 +
 +
Irving Hardestt, Robert J. Terry,
 +
 +
Warren H. Lewis, Frederick T. Lewis.
 +
 +
On motion, the Secretary was instructed to cast a ballot for the election to the respective offices of the members nominated by the Committee on nominations.
 +
 +
Charles S. Minot moved ^'That the American Association of Anatomists recommend to the International Congress of Anatomy the appointment of an International Committee to revise embryological nomenclature and prepare a list of standard terms. Seconded and carried.
 +
 +
On motion of Thomas G. Lee, the business meeting was adjourned.
 +
 +
Thursday, December 30, 9:30 a.m. to 1 p.m. Session for the
 +
 +
READING OF PAPERS, SeCOND ViCE-PrESIDENT, FLORENCE R.
 +
 +
Sarin, and the President, James Playfair McMurrich,
 +
 +
PRESIDING. The FOLLOWING PAPERS WERE PRESENTED:
 +
 +
J. F. McClendon, Cornell University Medical School {New York City). The toti potency of the first two blastomeres of the frog's egg. J. Parsons Schaeffer, Cornell University Medical School (Ithaca). Or the genesis
 +
 +
of air cells in the nasal conchae. George S. Huntington and H.v.W. Schulte, Columbia University (New York
 +
 +
City). Contribution to the morphology of the mammalian salivary glands.
 +
 +
1. H. v. W. Schulte. Development of the salivary glands of the cat.
 +
 +
2. George S. Huntington. Anatomy of the salivary glands in primates. (Only a brief abstract presented.)
 +
 +
Leo Loeb and William F. H. Addison, University of Pennsylvania. The transplantation of skin of the Guinea pig and the pigeon into other species. Charles R. Stockard, Cornell University Medical School (New York City).
 +
 +
1. The influence of alcohol and other anaesthetics on the developing embryo.
 +
 +
2. The independent origin and self differentiation of the crystalline Tens. George L. Streeter, University of Michigan. A new method of dissection of
 +
 +
the spinal cord and brachial plexus (Lantern slides).. Robert J. Terry, Washington University Medical School. The morphology of the
 +
 +
pineal region in fishes. John Warren, Harvard Medical School. On the paraphysis and*pineal region in
 +
 +
lacerta and chrysemis marginata.
 +
 +
 +
PROCEEDINGS 101
 +
 +
Franklin P. Johnston, Harvard Medical School, Development of the glands and
 +
 +
villi of the human digestive tract. Leonard W. Williams, Harvard Medical School. The somites of the chick. James Murphy, Johns Hopkins Medical Scliool. On the relation of the sulcus
 +
 +
lunatus to the visual area in the negro and white brains. G. Carl Huber, University of Michiaan. (Only brief abstracts presented).
 +
 +
1. On the relation of the notochord to the anlage of the pharyngeal bursa.
 +
 +
2. A note concerning the caudal end of the notochord in human embryos.
 +
 +
3. Concerning embryonic remains of the caudal end of the neural canal in the human embryo.
 +
 +
The following papers announced were read by title :
 +
 +
Charles F. Silvester, Princeton University, On the presence of permanent lymphatico-venous communications at the renal level in the South American monkeys.
 +
 +
Frederick Tilney, Columbia University (New York City). Comparative histology of the hypophysis.
 +
 +
Charles R. Bardeen, University of Wisconsin. Pi actical state board examination in anatomy.
 +
 +
Owing to the absence of Dr. Bardeen and at the suggestion of the Executive Conmiittee, the Association voted that Dr. Bardeen's paper be printed in the Anatomical Record and that the President appoint a committee to collect data and consider the question of State Board examinations and report to this Association at a future meeting.
 +
 +
The President appointed as such Committee, Charles R. Bardeen (Chairman), Franklin P. Mall, and George A. Piersol.
 +
 +
Thursday, December 29, 2 to 5 p.m. Demonstrations AS follows:
 +
 +
Robert J. Terry, Washington University Medical School, (a) Specimens and drawings illustrating the morphology of the pineal region in teleosts. (6) The velum trans versum of Opsanus, a true choroid plexus.
 +
 +
John Warren, Harvard Medical School. Models showing the paraph ysis and pineal region in lacerta and chrysemis marginata.
 +
 +
CHARLEe R. Stockard, Cornell University Medical School (New York City.) A sagittal section of a 2.2 mm. human embryo with 8 primitive se^ents.
 +
 +
H. V. W. ScHULTE, Columbia University (New York). Preparations illustrating the development of the salivary glands in the cat.
 +
 +
Clarence M. Jackson, University of Missouri. Electric heater and thermoregulator for paraffin ovens.
 +
 +
Leo Loeb and William H. F. Addison, University of Pennsylvania. Microscopic preparations of the skin of Guinea pig and pigeon after transplantation to other species.
 +
 +
Franklin P. Johnson, Harvard Medical School. Models showing the development of glands and villi of the human digestive tract.
 +
 +
 +
102 AMERICAN ASSOCIATION OF ANATOMISTS
 +
 +
Charles A. Todd, Washington University Medical SckooL Specimens illustrating a plan for a human anatomical museum.
 +
 +
G. Carl Huber, University of Michigan. Prepaiations showing (a) The relation of the notochord to the anlage of the pharyngeal bursa; (6) The caudal end of the notochord in human embryos ; (c) Embryonic remains of the caudal end of the neural canal in human embiyos.
 +
 +
G. Carl Huber, Secretary'Treasurer, American Association of Anatomists.
 +
 +
 +
AMERICAN ASSOCIATION OF ANATOMISTS
 +
 +
OFFICERS AND LIST OF MEMBERS
 +
 +
Officers
 +
 +
President George A. Piersol
 +
 +
Vice-President Charles F. W. McClure
 +
 +
Secretary-Treasurer G. Carl Huber
 +
 +
Executive CammiUee
 +
 +
Thomas G. Leb, Irving Hardbstt,
 +
 +
Simon H. Gagb, Robert J. Terry,
 +
 +
Robert R. Bbnblet, Warren H. Lbwis,
 +
 +
Henrt H. Donaldson, Frederick T. Lewis.
 +
 +
COBfMITTEES
 +
 +
Committee of Arrangements from this Association for IrUemcUional Congress of
 +
 +
Anatomy f Brussels^ August 7-10, 1910.
 +
 +
Charles. S. Minot (Chairman), Franklin P. Mall, James Playfair McMurrich,
 +
 +
George A. Piersol, Greorge S. Huntington, G. Carl Huber (Secretary).
 +
 +
American Members of the IntemcUional Committee on Reformation of the Myological
 +
 +
Nomenclature
 +
 +
James Platfair McMurrich, Ross G. Harrison
 +
 +
Delegate to the Council of the American Association for the Advancement of Science
 +
 +
Simon H. Gage
 +
 +
Members of Smithsonian Committee on the Table at Naples
 +
 +
George S. Huntington
 +
 +
Honorary Members
 +
 +
S. Ramon y Cajal Madrid, Spain
 +
 +
John Cleland Glasgow, Scotland
 +
 +
John Daniel Cunningham Edinburgh, Scotlarui
 +
 +
Camillo Golgi Pavia, Italy
 +
 +
Oscar Hertwig Berlin, Germany
 +
 +
Alexander Macallister Cambridge, England
 +
 +
A. Nicholas Paris, France
 +
 +
L. Ranvier Paris, France
 +
 +
Gustav Retzius Stockholm, Sweden
 +
 +
Carl Toldt •. Vienna, Austria
 +
 +
Sir William Turner Edinburgh, Scotland
 +
 +
WiLHELM Waldbybr Berlin, Germany
 +
 +
{| class="wikitable mw-collapsible mw-collapsed"
 +
! American Association Of Anatomists - Members (1910)  
 +
|-
 +
| Addison, William Henry Fitzgerald, B.A., M.B., Demonstrator of Histology and Embryology, University of Pennsylvania, S9B8 Pine Street, Philadelphia, Pa.
 +
 +
Allen, Bennet Mills, Ph.D., Instructor in Anatomy, University of Wisconsin, 710 Nouhlin Place, Madison, Wis.
 +
 +
Allen, William F., A.M., Collector and Assistant, Marine Laboratory, University of California, New Monterey, Calif.
 +
 +
Allis, Edward Phelps, Jr., LL.D., Palais de CarnoUs, Menione, France.
 +
 +
Allison, Nathaniel, M.D., Instructor in Orthopedic Surgery, Washington University, Ldnmar Building, St. Louis, Mo.
 +
 +
Baker, Frank, A.M., M.D., Ph.D. (Vice-Pres. '88-'91, Pres. '96-'97), Professor of Anatomy, University of Georgetown, 1788 Columbia Road, Washington, D.C.
 +
 +
Baldwin, Wesley Manning, Instructor in Anatomy, Cornell University Medical School, First Avenue and 28th Street, New York City, N. Y.
 +
 +
Bardeen, Charles Russell A.B., M.D. (Ex. Com. *06-'09.) Professor of Anatomy, University of Wisconsin, Science Hall, Madison, Wis.
 +
 +
Barker, Lewellys Franklin, M.D., (Ex. Com. '02-'05), Professor of Medicine, Johns Hopkins University, 10S5 North Calvert Street, Baltimore, Md.
 +
 +
Bates, George Andrew, M.S., Professor of Histology, Tufts College, J^IS Huntington Avenue, Boston, Mass.
 +
 +
Baumgartner, William J., A.M. Assistant Professor of Histology and Zoology, University of Kansas, Lawrence, Kas.
 +
 +
Bean, Robert Bennett, B.S., M.D., Professor of Anatomy, Medical School, Manila, P.I.
 +
 +
Bell, Elexious Thompson, B.S., M.D., Assistant Professor of Anatomy, University of Missouri, Columbia Club, Columbia, Mo.
 +
 +
Benbley, Benjamin Arthur, Ph.D., Associate Professor of Zodlogy, University of Toronto, 816 Brunswick Avenue, Toronto, Can.
 +
 +
Bensley, Robert Russell, A.B., M.D. (Second Vice-Pres. '06-'07, Ex. Com. '08'12). Professor of Anatomy, University of Chicago, Chicago, III.
 +
 +
Bevan, Arthur Dean, M.D. (Ex. Com. '96-'98), Professor of Surgery, University of Chicago, 100 State Street, Chicago, III.
 +
 +
BiGELOW, Robert P., Ph.D., Instructor in Biology, Massachusetts Institute of Technology, 4^1 Boylston Street, Boston, Mass.
 +
 +
Blair, Vilray Papin, A.M., M.D., Lecturer on Descriptive Anatomy, Washington
 +
 +
University, S7B9 Delmar Boulevard, St. Louis, Mo.
 +
Blake, Joseph Augustus, A.B. M.D., Professor of Surgery, Columbia Uniyersity, 601 Madison Avenue, New York City, N.Y.
 +
 +
Bloodgood, Joseph C, A.B., M.D., Associate Professor of Surgery, Johns Hopkins University, 904 N. Charles Street, Baltimore, Md.
 +
 +
Bremer, John Lewis, M.D., Harvard Medical School, 4^6 Beacon Street, Boston, Mass.
 +
 +
Brickner, Samuel Max, A.M., M.D., Gynecologist to Mt. Sinai Hospital Dispensary, 136 W. 86th. Street i New York City.
 +
 +
Br5del, Max, Associate Professor of Art as Applied to Medicine, Johns Hopkins University, Baltimore, Md.
 +
 +
Brooks, William Allen, M.D., 167 Beacon Street j BostoUy Mass.
 +
 +
Browning, Wiluam, Ph.D., M.D., Professor of Diseases of the Mind and Nervous System, Long Island College Hospital, 54 Lefferts Place, Brooklyn, N. Y.
 +
 +
Bruner, Henry Lane, Ph.D., Professor of Biology, Butler College, S50 South Ritter Avenue, Indianapolis, Ind.
 +
 +
Bunting, Charles Henry, B.S., M.D., Professor of Pathology, University of Wisconsin, Madison, Wis.
 +
 +
Burrows, Montrose I., M.D., Fellow, Rockefeller Institute, 66th Street and Avenue A, New York City, N. Y.
 +
 +
Campbell, William Francis, A.B., M.D., Professor of Anatomy and Histology, Long Island College Hospital, S94 Clinton Avenue, Brooklyn, N. Y.
 +
 +
Carpenter, Frederick Walton, Ph.D.,. Instructor in Zodlogy, University of Illinois, 1008 West Orange Street, Urbana, III.
 +
 +
Carr, William Phillips, M.D., Professor of Physiology, Medical Department, Columbia University, I4I8 L Street, N.W., Washington, B.C.
 +
 +
Chamberlain, Ralph V., Ph.D., Professor of Zodlogy, University of Utah, Salt Lake City, Utah.
 +
 +
Cheever, David, A.B., M.D., Demonstrator of Anatomy, Harvard Medical School, 20 Hereford Street, Boston, Mass.
 +
 +
Child, Charles Manning, Ph.D., Assistant Professor of Zoology, University of Chicago, Chicago, III.
 +
 +
Clapp, Cornelia Maria, Ph.D., Professor of Zodlogy, Mount Holyoke College, SoiUh Hadley, Mass.
 +
 +
Clark, Elbert, B.S., Assistant in Anatomy, University of Chicago, Chicago, III.
 +
 +
Clark, Eliot R., M.D., Instructor in Anatomy, Johns Hopkins University, Baltimore, Md.
 +
 +
CooHiLL, George E., Ph.D., Professor of Zoology, Denison University, Granville, Ohio.
 +
 +
CoHOE, Benson A., A.B., M.D., Professor of Anatomy, University of Pittsburg, 706 North Highland Avenue, Pittsburg, Ohio.
 +
 +
CoNANT, Wiluam Merritt, M.D., Instructor in Anatomy in Harvard Medical School, 4^6 Commonwealth Avenue, Boston, Mass.
 +
 +
CoNKUN, Edwin Grant, A.M., Ph.D., Sc.D., Professor of Zodlogy, Princeton University, Princeton, N. J.
 +
 +
Corning, H. M., M.D., Professor and Prosector of Anatomy, Basel, Switzerland.
 +
 +
Corson, Eugene Rollins, B.S., M.D., // Jones Street, East Savannah, Ga.
 +
 +
Craig, Joseph Davis, A.M. M.D., Professor of Anatomy, Albany Medical College, 12 Ten Broeck Street, Albany, N. Y.
 +
 +
CuLLEN, Thomas S., M.B., Associate Professor of Gynecology, Johns Hopkins University, S West Preston Street, Baltimore, Md.
 +
 +
Dahlgren, Ulric, M. S., Assistant Professor of Biology, Princeton University, 7 Evelyn Place, Princeton, N. J.
 +
 +
Dandy, Walter E., A.B., Johns Hopkins Med'cal School, Baltimore, Md.
 +
 +
Darrach, William, A.M., M.D., Demonstrator of Anatomy, Columbia University, 61 West 48th Street, New York City, N. Y.
 +
 +
Davidson, Alvin, M.A., Ph.D., Professor of Biology, Lafayette College, Easton, Pa.
 +
 +
Davis, David M., B.S., Johns Hopkins Medical School, Baltimore, Md,
 +
 +
Dawburn, Robert H. Mackay, M.D., Professor of Anatomy, New York Polyclinic Medical School and Hospital, 106 West 74th Streety New York City, N. Y,
 +
 +
Dean, Bashford, Ph.D., Professor of Vertebrate Zodlogy, Columbia University, £0 W. 82nd Street, New York City, N. Y.
 +
 +
Dbwitt, Lydia M., M.D., B.S., Instructor in Histology, University of Michigan, Ann Arbor, Michigan.
 +
 +
Dexter, Franklin, M.D., IJtS Marlborough Street, Boston, Mass.
 +
 +
Dixon, A. Francis, M.B., Sc. D., University Professor of Anatomy, Trinity College, 7S Grosvener Road, Dublin, Ireland.
 +
 +
Dodson, John Milton, A.M., M.D., Professor of Medicine, University of Chicago, 5806 Washington Boulevard, Chicago, III.
 +
 +
Donaldson, Henry Herbert, Ph.D., Sc.D. (Ex. Com. '09-' 13), Professor of Neurology, The Wistar Institute of Anatomy, Philadelphia, Pa.
 +
 +
Dunn, Elizabeth Hopkins, A.M., M.D., Associate in Anatomy, University of Chicago, Chicago, III.
 +
 +
DwiGHT, Thomas, M.D., LL.D. ( Ex. Com. '91-'93, Pres. '94-'95), Parkman Professor of Anatomy, Harvard Medical School, Boston, Mass.
 +
 +
EccLBS, Robert G., M.D., Professor Organic Chemistry, Brooklyn College of Pharmacy, 191 Dean Street, Brooklyn, N. Y.
 +
 +
Edwards, Charles Lincoln, Ph.D., Professor of Natural History, Trinity College, 89 BiLckingham Street, Hartford, Conn.
 +
 +
Eigenmann, Carl H., Ph.D., Professor of Zoology, Indiana University, Bloomington, Ind.
 +
 +
Eluot, Gilbert M., A.M., M.D., Assistant Demonstrator of Anatomy, Medical School of Maine, 152 Maine Street, Brunswick, Me.
 +
 +
Emmel, Victor E., Ph.D., Instructor in Embryology and Histology, Washington University, St. Louis, Mo.
 +
 +
Erdman, Charles Andrew, M.D., Professor of Anatomy, Medical Department, University of Minnesota, Minneapolis, Minn.
 +
 +
EssiCK, Charles Rhein, B.A., M.D., Assistant in Anatomy, Johns Hopkins University, Baltimore, Md.
 +
 +
Etherington, Frederick, M.D., Professor of Anatomy, Queen's University, 218 Albert Street, Kingston, Canada.
 +
 +
Evans, Herbert McLean, B.S., M. D., Instructor in Anatomy, Johns Hopkins University, Baltimore, Md.
 +
 +
Eycleshymer, Albert Chauncy, B.S., Ph.D., Professor of Anatomy, University of St. Louis, St. Louis, Mo.
 +
 +
Ferguson, Jeremiah Sweetser, M.Sc, M.D., Instructor in Histology, Cornell University Medical College, 55 W. 28th Street, New York City, N. Y.
 +
 +
Ferris, Harry Burr, A.B., M.D., Professor of Anatomy, Medical Department, Yale University, S95 St. Ronan, New Haven, Conn.
 +
 +
Fischelis, Philip, M.D., Associate Professor of Histology and Embryology, Medico-Chirurgical College, 828 N. 6th Street, Philadelphia, Pa.
 +
 +
FuNT, Joseph Marshall, B.S., A.M., M.D. (Second Vice-Pres. '03-'04.) Professor of Surgery, Yale University, Sll Temple Street, New Haven, Conn.
 +
 +
Fox, Henry, Ph.D., Professor of Biology, Ursinus College, Collegeville, Pa.
 +
 +
Frost, Gilman Dubois, A.M., M.D., Professor of Anatomy, Dartmouth Medical School, Hanover, N. H.
 +
 +
Gage, Simon Henry, B.S., (Ex. Com. '06-'ll), Emeritus Professor of Histology and Embryology, Cornell University, Ithaca^ N, F.
 +
 +
Gage, Mrs. Susanna Phelps, B.Ph., 4 South Aventief Ithaca, N, Y,
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 +
Gallaudet, Bern Btjdd, A.M., M.D., Demonstrator of Anatomy, Colimibia University, The Stuyvesant, 17 Livingston Place, New York City, iV. Y,
 +
 +
Gehring, Norman J., A.B., M.D., 706 N. Robinson Street, Oklahoma City, Oklahoma.
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 +
Gbrrish, Frederick Henby, A.M., M.D., LL.D. (Ex. Com. '93-'95, '97-'99, '02-'06, Vice Pres. '00-* 01), Professor of Surgery, Bowdoin College, 675 Congress Street, Portland, Me.
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 +
Gibson, James A., M.D. Professor of Anatomy, University of Buffalo, 170 Mariner Street, Buffalo, N. Y.
 +
 +
GiLMAN, Philip Kingsworth, B.A., M.D., Assistant in Operative Surgery, Medical School, Manila, P. I.
 +
 +
GoETTSCH, Emil, Ph.D., M.D., Assistant in Surgery, Johns Hopkins University, Baltimore, Md.
 +
 +
Greenman, Milton J., Ph.B., M.D., Director of the Wistar Institute of Anatomy, S6th Street and Woodland Avenue, Philadelphia, Pa.
 +
 +
GuYER, Michael F., Ph.D., Professor of Zoology, University of Cincinnati, 56i Evanswood, Clifton, Cincinnati, Ohio.
 +
 +
Halstead, William Stewart, M.D., Professor of Surgery, Johns Hopkins University, 1201 Eutaw Place, Baltimore, Md.
 +
 +
Hamann, Carl A., M.D. (Ex. Com. '02-'04), Professor of Anatomy, Medical Department, Western Reserve University, 40J^ Osborn Building, Cleveland, Ohio.
 +
 +
Hardesty, Irving, A.B., Ph.D., Professor of Anatomy, Tulane University, New Orleans, La.
 +
 +
Hare, Earl R., A.B., M.D., Instructor in Anatomy, University of Minnesota, SIS7 14th Avenue, Minneapolis, Minn.
 +
 +
Harper, Eugene Howard, Ph.D., Instructor in Zoology, Northwestern University, 1105 Grant Street, Evanston, III.
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 +
Harrison, Ross Granville, Ph.D., M.D., Professor of Comparative Anatomy, Yale University, 2 Hillhouse Avenue, New Haven, Conn.
 +
 +
Harvey, Basil Coleman Hyatt, A.B., M.B., Instructor in Anatomy, University of Chicago, ^4 E. 60th Street, Chicago, III.
 +
 +
Hatai, Shinkishi, Ph.D., Associate in Neurology, Wistar Institute of Anatomy, Philadelphia, Pa.
 +
 +
Hathaway Joseph H., A.M., M.D., Professor of Anatomy, University of Louisville, Louisville, Ky.
 +
 +
Haynes, Irving Samuel, Ph.B., M.D., Professor of Practical Anatomy, Cornell University Medical College, 107 W. 85th Street, New York City, N. Y.
 +
 +
Hazen, Charles Morse, A.M., ^1.D., Professor of Physiology, Medical College of Virginia, Richmond, Bon Air, Va.
 +
 +
Heisler, John C, M.D., Professor of Anatomy, Medico-Chirurgical College, Philadelphia, Pa., S829 Walnut Street, Philadelphia, Pa.
 +
 +
Herrick, Charles Judson, Ph.D., Professor of Neurology, University of Chicago, Chicago, III.
 +
 +
 +
Hbrtzler, Arthur E., A.M., M.D., Ph.D., Professor of General and Surgical
 +
 +
Pathology and Experimental Sur^e-y, University Medical College, 402 Argyle
 +
 +
Building f Kansas Cityy Mo, Heuer, George Julius, B.S., M.D., Assistant Resident-Surgeon, Johns Hopkins
 +
 +
Hospital, Baltimore^ Md. Hewson, Addinell, A.m., M.D., Professor of Anatomy of Philadelphia Polyclinic for Graduates of Medicine ; Secretary of Pennsylvania State Anatomical
 +
 +
Board, 21f^ Spruce Street, Philadelphiay Pa, Hill, Eben Clayton, A.B., M.D., First Lieutenant, Medical Reserve Corps, U. S.
 +
 +
A., Washington, D, C. Hill, Howard, M.D., Professor of Anatomy, University Medical College, 4$6
 +
 +
Argyle Building, Kansas City, Mo. Hilton, William A., Ph.D., Instructor in Histology, Cornell University, Ithaca,
 +
 +
N. Y. Hodge, C. F., Ph.D., Professor of Biology, Clark University, Worcester, Mass. Hoeve, Heikobus, J. H. M.D., Professor of Anatomy, Drake University, Des
 +
 +
Moines, Iowa. Hooker, Davenport, M.A., Instructor in Anatomy, Medical Department, Yale
 +
 +
University, 1S3 Canner Street, New Haven, Conn. Hopkins, Grant Sherman, Sc.D., D.V.M., Professor of Veterinary Anatomy,
 +
 +
Cornell University, 125 Dry den Road, Ithaca, N. Y. Howard, Wm. T., M.D., Professor of Pathology, Western Reserve University,
 +
 +
Cleveland, Ohio. Hrdlikca, Ales, M.D., Curator of the Division of Physical Anthropology, United
 +
 +
States National Museum, Washington, D. C. HuBER, G. Carl, M.D. (Second Vice-Pres. '00— '01, Secretary-Treasurer '02-' 13).
 +
 +
Professor of Histology and Embryology, University of Michigan, 13S0 Hill
 +
 +
Street, Ann Arbor, Mich. Huntington, George S., A.M., M.D., D.Sc, LL.D. (Ex. Com. '95-'97, '04-'07,
 +
 +
Pres. '99-'03), Professor of Anatomy, Columbia University, 4S7 W. 69th • Street, New York City, N. Y. Ingalls, N. William, M.D., Instructor in Anatomy, Medical College, Western
 +
 +
Reserve University, St. Clair Avenue and East 9th Street, Cleveland, Ohio. Jackson, Clarence M., M.S., M.D., Professor of Anatomy and Histology, University of Missouri, 811 College Avenue, Coluanbia, Mo. Jayne, Horace, M.D., Ph.D., Walling ford. Pa. Johnson, Franklin P., A.B., Austin Teaching Fellow, Harvard Medical School,
 +
 +
Boston, Mass. Johnston, John B., Ph.D., Professor of Comparative Neurology, University of
 +
 +
Minnesota, Minneapolis, Minn. Jordan, Harvey Ernest, Ph.D., Adjunct Professor of Anatomy, University of
 +
 +
Virginia, Charlottesville, Va. •
 +
 +
Keiller, William, L.R.C.P. and F.R.C.S.Ed. (Second Vice-Pres. '98-'99.) Professor of Anatomy, University of Texas, Galveston, Tex. Kelly, Howard Atwood, A.B., M.D., LL.D., Professor of Gynecology, Johns
 +
 +
Hopkins University, I4I8 Eutaw Place, Baltimore, Md. Kemp, George T., M. D.,Ph.D., Hotel Beardsley, Champaign, III, Kerr, Abram T., B.S., M.D., Professor of Anatomy, Cornell University, Ithaca, N.Y.
 +
 +
 +
Kingsbury, Benjamin F., Ph.D., M.D., Professor of Histology and Embryology, Cornell University, Ithaca, N. Y.
 +
 +
KiNOSLET, J. S., Sc.D., Professor of Biology, Tufts College, Mass.
 +
 +
Kirk, Edwin Garvey, B.S., Associate Instructor in Anatomy, University of Chicago, 6S7 Jackson Boulevard, Chicago, III.
 +
 +
Knower, Henry McE, A.B., Ph.D., ^Lecturer in Anatomy, Toronto University, Toronto, Canada.
 +
 +
KoFOiD, Charles Atwood, Ph.D., Professor of Histology and Embryology, University of California, Berkeley, Cal.
 +
 +
Kutchin, Harriet Lehmann, A.M., Assistant in Biology, University of Montana, Missoula, Mont.
 +
 +
Kyes, Preston, A.M., M.D., Assistant Professor of Experimental Pathology, University of Chicago, Quadrangle Club, Chicago, III.
 +
 +
Lamb, Daniel Smith, A.M., M.D. (Secretary -Treasurer '90-'01, Vice-Pres. '02'03.) Pathologist Army Medical Museum, Professor of Anatomy, Howard University, Medical Department, £114 l^lh Street, N.W., Washington, D. C.
 +
 +
Lambert, Adrian V. S., A.B., M.D., Instructor in Surgery, Columbia University, 29 W. Seth Street, New York City, N. Y.
 +
 +
Land acre, Francis Leroy, A.B., Associate Professor of Zo5logy, Ohio State University, Columbus, Ohio.
 +
 +
Lane, Michael Andrew, B.S., Assistant in Histology and Embryology, University of Chicago, lSi6 Jackson Boulevard, Chicago, III.
 +
 +
LeCron, Wilbur L., A.B., M.D., Hartford Hospital, Hartford, Conn.
 +
 +
Leb, Thomas G., B.S., M.D., (Ex. Com. '08-'10.) Professor of Anatomy and Director of the Department of Anatomy, University of Minnesota, Minneapolis, Minn.
 +
 +
LeFevre, George, Ph.D. Professor of Zoology, University of Missouri, Columbia, Mo.
 +
 +
Leidy, Joseph Jr., A.M., M.D. 1319 Locust Street, Philadelphia, Pa.
 +
 +
Lempe, George Gustave, A.B., M.D., Lecturer on Anatomy, Albany Medical College, 4£ Eagle Street, Albany, N. Y.
 +
 +
Lewis, Dean D., M.D., Assistant Professor of Surgery, Rush Medical College, 100 State Street, Chicago, III.
 +
 +
Lewis, Frederick T., A.M., M.D., Assistant Professor of Embryology, Harvard Medical School, Boston, Mass.
 +
 +
Lewis, Warren Harmon, B.S., M.D., Associate Professor of Anatomy, Johns Hopkins University, Baltimore, Md.
 +
 +
Lewis, William Evan, M.D., Professor of Anatomy, Miami Medical College, 409 E. 6th Street, Cincinnati, Ohio.
 +
 +
LiLLiE Frank Rathay, Ph.D., Professor of ZoSlogy and Embryology, University of Chicago, Chicago, III.
 +
 +
LissER, Hans, Johns Hopkins Medical School, Baltimore, Md.
 +
 +
LocY, WiLUAM A., Ph.D., Sc.D., Professor of Zoology and Director of the Zodlogical Laboratory, Northwestern University, Evanston, III.
 +
 +
LoEB, Hanau Wolf, A.M., M.D., Professor of Nose and Throat Diseases, St. Louis University, 6S7 N. Grand Avenue, St. Louis, Mo.
 +
 +
LoEB, Leo, M.D., Assistant Professor of Experimental Pathology, University of Pennsylvania, Philadelphia, Pa.
 +
 +
McCarthy, John George, M.D., Lecturer on Anatomy, McGill University, 61 Drummond Sireety Montreal^ Canada,
 +
 +
McClellan, George, M.D., Prof essor of Applied Anatomy, Jefferson Medical College, 1116 Spruce Street^ Philadelphia^ Pa,
 +
 +
McClendon, J. F., Ph.D., Assistant in Histology, Cornell University Medical School, New York City, N, Y,
 +
 +
McClurb, Charles Freeman Williams, A.M., Ph.D., Sc.D., Professor of Comparative Anatomy, Princeton University, Princeton, N. J,
 +
 +
McDonald, Archibald L., A.B., M.D., Professor of Anatomy and Physiology, University of North Dakota, Grand Forks, iV. Dak.
 +
 +
McDoNouGH, Edward Joseph, A.B., M.D., Instructor in Histology, Medical School of Maine, 624 Congress Street, Portland, Me,
 +
 +
McGiLL, Caroline, A.M. Ph.D., Instructor in Anatomy, University of Missouri, Columbia, Mo,
 +
 +
McMurrich, James Playfair, A M., Ph.D. (Ex. Com. '06- W, Pres '08-'09), Professor of Anatomy, University of Toronto, Toronto, Caruida,
 +
 +
McNeal, Ward J., Ph.D., M.D., Assistant Professor of Bacteriology, University of Illinois, 1005 W. Oregon Street, Urbana, III.
 +
 +
Major, Ralph Hermann, A.B., Johns Hopkins Medical School, Baltimore, Md.
 +
 +
Mall, Franklin P., A.M., M.D., LL.D., D.Sc. (Ex. Com. '00-'05, Pres. '06-W), Professor of Anatomy, Johns Hopkins University, Baltimore, Md,
 +
 +
Mann, Gustavb, M.D., B.Sc., Professor of Physiology, Tulane University, New Orleans, La.
 +
 +
Mark, Edward Laurens, Ph.D., LL.D., Hersey Professor of Anatomy and Director of the Zoological Laboratory, Harvard University, 109 Irving Street, Cambridge, Mass.
 +
 +
Martin, Walton, Ph.D., M.D., Instructor in Surgery, Columbia University, 68 E, 56th Street, New York City, N,Y.
 +
 +
Matas, Rudolph, M.D., Professor of Surgery, Tulane University, S255 St. Charles Avenue, New Orleans, La,
 +
 +
Mellus, Edward Lindon, M.D., Anatomical Laboratory, Johns Hopkins University Medical School, Baltimore, Md.
 +
 +
Mercer, William F., Ph.D., Professor of Biology, Ohio University, iSOO E. State, Street, Athens, Ohio.
 +
 +
Meyer, Adolf, M.D., LL.D., Professor of Psychiatry, Johns Hopkins University Baltimore, Md.
 +
 +
Meyer, Arthur W., S.B., M.D., Professor of Anatomy, Leland Stanford University, Palo Alto, Calif.
 +
 +
Miller, Adam M., A.M., Instructor in Anatomy, Columbia University, New York City, N. Y.
 +
 +
Miller, Walter McNat., B.Sc, M.D., Professor of Pathology and Bacteriology, University of Missouri, Columbia, Mo.
 +
 +
Miller, William Snow, M,.D. (Vice-Pres. '08-'09), Associate Professor of Anatomy, University of Wisconsin, University Club, Madison, Wis.
 +
 +
Minot, Charles Sedgwick, S.B., (Chem), S.D., LL.D., D.Sc. (Ex. Com. '9^'02, '06-'08, Pres. '04-'05), Professor of Comparative Anatomy, Harvard Medical School, Boston, Mass,
 +
 +
MiXTEB, Samuel Jason, B.S., M.D., Instructor of Surgery, Harvard Medical School, 180 Marlborough Streety Boston^ Mass.
 +
 +
Moody, Mart Blair, M.D., 166 S. Marengo Avenue, Pasadena, Cal.
 +
 +
Moody, Robert Orten, B.S., M.D., Assistant Professor of Anatomy, University of California, Berkeley, Cal.
 +
 +
Morgan, James Dudley, A.B., M.D., Clinical Professor, Georgetown University, 919 15th Street, McPherson Square, Washington, D. C.
 +
 +
Morgan, Thomas H., Ph.D., Professor of Experimental Morphology, Columbia University, New York City, N. Y.
 +
 +
Morse, Max, Ph.D., Instructor in Biology, College of the City of New York, New York City, N. Y.
 +
 +
MuNROB, John Cummings, A.B., M.D., Surgeon in Chief, Carney Hospital, 17S Beacon Street, Boston, Mass.
 +
 +
MuNsoN, John P., Ph.D., Head of the Department of Biology, Washington State Normal School, Ellensburg, Washington.
 +
 +
Murphy, James B., B.S., Pathological Institute, Wards Island, New York City, N. Y.
 +
 +
Myers, Burton D., A.M., M.D., Professor of Anatomy, Indiana University, Bloomington, Ind.
 +
 +
Nachtrieb, Henry Francis, B.S., Professor of Animal Biology, University of Minnesota^ 905 S.E. 6th Street, Minneapolis, Minn.
 +
 +
Nbal, Herbert Vincent, Ph.D., Professor of Biology, Knox College, 750 N. Academy Street, Galeshurg, III.
 +
 +
Noble, Harriet Isabel, M.D., Demonstrator of Anatomy, Woman's Medical College of Pennsylvania, Noble, Pa.
 +
 +
Parker, Charles Aubrey, M.D., Instructor in Anatomy, University of Chicago, 100 State Street, Chicago, III.
 +
 +
Parker, George Howard, D. Sc, Professor of Zodlogy, Harvard University, 16 Berkeley Street, Cambridge, Mass.
 +
 +
Paton, Stewart, A.B., M.D., Princeton University, Princeton, N. J.
 +
 +
Patten, Wiluam, Ph.D., Professor of Zodlogy, Dartmouth College, Hanover, N.H*
 +
 +
Patterson, James. B.S., Assistant in Anatomy, University of Chicago, Chicago, III.
 +
 +
PiBRSOL, George A., M.D., Sc.D., (Vice-Pres. '98-'99, '93-'94, '06-W.) Professor of Anatomy, University of Pennsylvania 47H Chester Avenue, Philadelphia, Pa.
 +
 +
PoHLMAN, August G., M.D., Junior Professor of Anatomy, Indiana University, 411 Fess Avenue, Bloomington, Ind.
 +
 +
Potter, Peter, M.S., M.D., 51 Owsley Block, Butte, Montana.
 +
 +
Prentiss, H. J., M.D., M.E. Professor of Anatomy, University of Iowa, Iowa City, la.
 +
 +
Primrose, Alexander, M.B., C.M.Ed., M.R.C.S.Eng., Professor of Surgery, University of Toronto, 100 College Street, Toronto, Canada.
 +
 +
Pryor, Joseph Wiluam, M.D., Professor of Anatomy and Physiology, State College of Kentucky, 261 N. Broadway, Lexington, Ky.
 +
 +
Radasch, Henry E., M.S. M.D., Associate in Histology and Embryology, Jefferson Medical College, 914 S. 47th Street, Philadelphia, Pa.
 +
 +
Ranson, Stephen W., M.D., Ph.D., Assistant Professor of Anatomy, Northwestern University Medical School, Chicago^ III.
 +
 +
Reese, Albert Moore, A.B., Ph.D., Professor of Zodlogy, West Virginia University', MorgantotDTij W. Va.
 +
 +
Reford, Lewis L., A.B., M.D. Assistant Resident Surgeon, Johns Hopkins Hospital, Baltimore^ Md.
 +
 +
Retzer, Robert, M.D., Assistant Professor of Anatomy, University of Minnesota, Minneapolis^ Minn.
 +
 +
Revell, Daniel Graisberry, A.B., M.B., Department of Public Health, Edmon" ton, Alberta, Canada.
 +
 +
Rice, Edward Loramus, Ph.D., Professor of Zoology, Ohio Wesley an University, 1S4 W. Lincoln Avenue, Delaware, Ohio.
 +
 +
Russell, Nelson G., M.D., Assistant in Anatomy, University of Buffalo, 476 •Franklin Street, Buffalo, N. Y.
 +
 +
Sarin, Florence R., B.S., M.D. (Second Vice-Pres. '08-'09), Associate Professor of Anatomy, Johns Hopkins University, Baltimore, Md.
 +
 +
Sachs, Ernest, A.B., M.D., Surgeon, 1070 Madison Avenue, New York City, N". Y.
 +
 +
Sampson, John Albertson, A.B., M.D., 180 Washington Avenue, Albany N". Y.
 +
 +
Santee, Harris E., Ph.D., M.D., Professor of Anatomy, University of Illinois, 2819 Warren Avenue, Chicago, III.
 +
 +
ScANNON, Richard E., A.B., Instructor in Histology and Embryology, Harvard Medical School, Boston, Mass.
 +
 +
Schaeffer, Jacob P., A.B., M.E., M.D., Instructor in Anatomy, Cornell University, Ithaca, N. Y.
 +
 +
Schaeffer, Marie Charlotte,M.D., Lecturer on Biology and Normal Histology, University of Texas, Galveston, Texas.
 +
 +
Schoemaker, Daniel M., B.S., M.D., Associate Professor of Anatomy, St. Louis University, St. Louis, Mo.
 +
 +
ScHULTE, Hermann Von W., A.B., M.D., Adjunct Professor of Anatomy, Columbia University, 176 W. 87th Street, New York City, N. Y.
 +
 +
ScHMiTTER, Ferdinand, A.B., M.D., First Lieutenant, Assistant Surgeon, U. S. Army, Fort Slocum, New York.
 +
 +
Seelio, Major G., A.B., M.D., Assistant in Anatomy, St. Louis University, 5S7 N. Grand Avenue, St. Louis, Mo.
 +
 +
Selling, Lawrence, A.B., Johns Hopkins Medical School, Baltimore, Md.
 +
 +
Senior, Harold D., M.B., F.R.C.S., Professor of Anatomy, Syracuse University, Orange Street, Syracuse, N. Y.
 +
 +
Shambaugh, George E., Ph.B. M.D., Instructor in the Anatomy of the Ear, Nose and Throat, University of Chicago, 100 State Street, Chicago, III.
 +
 +
Sheldon, Ralph Edward, A.M., M.S., Assistant Professor of Anatomy, University of Pittsburg, Brereton Avenue and 30th Street, Pittsburg, Pa.
 +
 +
Shepherd, Francis John, M.D., CM., M.R.C.S., Eng., LL.D. (Second Vice-Pres. '94-^97, Ex. Com. '97-'02.) Professor, of Anatomy, McGill University, 16ii Mansfield Street, Montreal, Canada.
 +
 +
Silvester, Charles Frederick, Assistant in Anatomy, Princeton University, 10 Nassau Hall, Princeton, N. J.
 +
 +
SissoN, Septimus, B.S., V.S. Professor of Comparative Anatomy, Ohio State University, Columbus, Ohio.
 +
 +
Sluder, Greenfield, M.D., S64ii Washington Avenue, St. Louis, Mo,
 +
 +
Smith, Charles Dbnnison, A.M., M.D., Professor of Physiology, Medical School of Maine, Maine General Hospital, Portland, Me.
 +
 +
Smith, Eugene Alfred, M.D., 1018 Maine Street, Buffalo, N. Y.
 +
 +
Smith, Frank, A.M., Associate Professor of Zoology, University of Illinois, 91S W. California Avenue, Urbana, III.
 +
 +
Smith, Helen Williston, A.B., Johns Hopkins Medical School, Baltimore, Md.
 +
 +
Smith, J. Holmes, M.D., Professor of Anatomy, University of Maryland, B206 St. Paul Street, Baltimore, Md.
 +
 +
Spitzka, Edward Anthony, M.D., Professor of General Anatomy, JefiFerson Medical College, 10th and Walnut Streets, Philcidelphia, Pa.
 +
 +
Starks, Edwin Chapin, Assistant Professor of Zoology, Leland Stanford University, Palo Alto, Cal.
 +
 +
Steensland, Halbert Severin, B.S., M.D., Associate Professor of Pathology and Bacteriology, and Director of the Pathological Laboratory, Syracuse University, 506 University Place, Syracuse, N. Y.
 +
 +
Stiles, Henry Wilson, M.D., Assistant Professor of Anatomy, Tulane University, New Orleans, La.
 +
 +
Stockard, Charles Rupert, Ph.D., Assistant Professor of Experimental Morphology, Cornell University Medical School, New York City, N. Y,
 +
 +
Stotzenburg, James M., M.D., Curator and Junior Associate in Anatomy, Wistar Institute of Anatomy, Philadelphia, Pa.
 +
 +
Streeter, George L., A.M., M.D., Prof essor of Anatomy , University of Michigan, Ann Arbor, Mich.
 +
 +
Stromsten, Frank Albert, D.Sc, Instructor in Animal Biology, University of Iowa, 2J^ East Burlington Street, Iowa City, la.
 +
 +
Strong, Oliver S., Ph.D., Instructor in Histology and Embryology, Columbia University, 4S7 W. 69th Street, New York City, N. Y.
 +
 +
Strong, Reuben Myron, Ph.D., Instructor in Zodlogy, University of Chicago, Chicago, III.
 +
 +
Sudler, Mervin T., M.D., Ph.D., Professor of Anatomy, University of Kansas, 1037 Tennessee Street, Lawrence, Kan.
 +
 +
Sundwall, John, Ph.D., Professor of Anatomy, University of Utah, Salt Lake City, Utah.
 +
 +
Taussig, Frederick Joseph, A.B., M.D., Clinical Assistant in Gynecology, Washington University, Metropolitan Building, St. Louis, Mo.
 +
 +
Taylor, Edward W., A.M., M.D., Instructor in Neurology, Harvard Medical School, 467 Marlborough Street, Boston, Ma.ss.
 +
 +
Taylor, Ewing, A.B., M.D., 19 Arden Place, Yonkers, N. Y.
 +
 +
Terry, Robert James, A.B., M.D., Professor of Anatomy, Washington University, 1806 Locust Street, St. Louis, Mo.
 +
 +
Thro, William C, A.M., iS9 W. 160 Street, New York City, N. Y.
 +
 +
Thyng, Frederick Wilbur, Ph.D., Assistant Professor of Anatomy, Northwestern University Medical School, Chicago, III.
 +
 +
Tilney, Frederick, A.B., M.D., Associate in Anatomy, Columbia University, 161 Henry Street, Brooklyn, N. Y.
 +
 +
Tobie, Walter E., M.D., Professor of Anatomy. Medical School of Maine, B Deering Street, Portland, Me,
 +
 +
TuppER, Paul Yoer, M.D., Professor of Applied Anatomy, Washington University, Ldnmar Building^ St. Louis, Mo.
 +
 +
TucKERMAN, FREDERICK, M.D., Ph.D., Amherst, Mass.
 +
 +
Waite, Frederick Clayton, A.M., Ph.D., Professor of Histology and Embryology, Western Reserve University, E. 9th Street and St. Clair Avenue, Cleveland, Ohio.
 +
 +
Walker, George, M.D., Instructor in Surgery, Johns Hopkins University, Cor, Charles and Centre Streets, Baltimore, Md,
 +
 +
Ward, Charles Howard,557 West Aventie, Rochester, N. Y,
 +
 +
Warren, John, M.D., Assistant Professor of Anatomy, Harvard Medical School, Boston, Mass.
 +
 +
Webster, John Clarence, B.A., M.D., F.R.C.P.Ed., Professor of Obstetrics and Gynecology, University of Chicago, 706 Reliance Building, Chicago, III.
 +
 +
Weed, Lewis Hill, A.M., Johns Hopkins Medical School, Baltimore, Md.
 +
 +
Weidenreich Franz, M.D., a.o. Professor and Prosector of Anatomy, 19 Vogesen Street, Strassburg, i. Els. Germany.
 +
 +
Wbisse, Faneuil D., M.D., (Second Vice-Pres. '88-'89.), Professor of Anatomy, New York College of Dentistry, 19 Gramercy Park, New York City, N. Y.
 +
 +
West, Charles Ignatius, M.D., Lecturer on Topographical Anatomy, Howard University, 9B4 M Street N.W., Washington, D. C.
 +
 +
Wbysse, Arthur Wissland, A.M., M.D., Ph.D., Professor of Biology, Boston University, 688 Boylston Street, Boston, Mass.
 +
 +
Whitehead, Richard Henry, A.B. M.D. Professor of Anatomy, University of Virginia, Charlottesville, Va.
 +
 +
Wilder, Burt G., M.D., B.S. (Ex. Com. '90-'92, Vice-Pres. *93-'97, Pres. '98-'99), Professor of Neurology, Vertebrate Zoology and Physiology, Cornell University, Ithaca, N. Y.
 +
 +
Wilder, Harris Hawthorne, Ph.D., Professor of Zodlogy, Smith College, 72 Aryads Green, Northampton, Mass.
 +
 +
Williams, Leonard Worcester, Ph.D., Instructor in Comparative Anatomy, Harvard Medical School, Boston, Mass.
 +
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Williams, Stephen Riggs, Ph.D., Professor of Biology and Geology, Miami University, Box 150, Oxford, Ohio.
 +
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Wilson, J. Gordon, M.A. M.B., CM. (Edin), M.D., Professor of Otology, Northwestern University Medical School, Chicago, III.
 +
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Wilson, James Meredith, Ph.D., M.D., Assistant Professor of Histology and Embryology, St. Louis University, St. Louis, Mo.
 +
 +
WiNSLOw, Guy Monroe, Ph.D., Instructor in Histology, Tufts Medical College, lJt6 Woodland Road, Auburndale, Mass.
 +
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WiTHERSPOON, Thomas Casey, M.D., S07 Granite Street, Butte, Montana.
 +
 +
Wolcott, Robert Henry, A.M., M.D., Professor of Anatomy, University of Nebraska, Station A, Lincoln, Neb.
 +
 +
Woods, Frederick Adams, M.D., Lecturer in Biology, Massachusetts Institute of Technology 1006 Beacon Street, Brookline, Mass.
 +
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WooLBEY, George, A.B., M.D., Professor of Anatomy and Clinical Surgery, Cornell University Medical College, 117 E. 36th Street, New York City, N. Y.
 +
|}
 +
 +
==NOTE ON THE SULCUS LUNATUS IN NEGRO AND WHITE BRAINS AND ITS RELATION TO THE AREA STRIATA==
 +
 +
JAMES B. MURPHY
 +
 +
From the Anatomical Laboratory of the Johns Hopkins University
 +
 +
WITH SIXTEEN TEXT FIGURES
 +
 +
The recent critical work of Professor Mall^ on the evidences of any racial characteristic of the brain that can be made out by our present methods, involving as it does both his own work and an analysis of the evidence in the literature, must make one skeptical of results that are positive in their nature.
 +
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Probably no area of the cortex has been subjected to so much study as the occipital cortex, in the hope of some evidence of racial characteristics. In 1904 Elliott Smith^ suggested a method of study of the occipital lobe which appeals to reason as being a little less crude than the methods of weighing and comparing surface form and folds, and one that yielded Professor Smith results which stimulate a further application of the method. The method in a word is this : the histological picture of the cortex in the calcarine region, namely, the visual area, is sufficiently marked to be distinguished in thin, freehand sections of a fresh brain, or of a brain hardened in formalin. The characteristic of this area is the so-called stripe of Gennari or line of Vicq d'Azyr. This stripe is readily seen with the naked eye and Smith pointed out that its limits are sharp rather than indefinite, so that it is not necessary to stain sections for fibers by the Weigert method in order to mark out the area striata. Having marked out the area striata by means of freehand sections, he studied the sulci of the calcarine area
 +
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' Mall. On several anatomical characters of the human brain, said to vary according to race and sex, with especial reference to the weight of the frontal lobe. Amer. Journ. of Anal. y vol. 9, 1909.
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^ Smith. Morphology of the retro-calcarine region of the cortexcerebri. Studies in morphology of the human brain. No 1. The occipital region. Records of Egypt, Gov. School of Med., vol. 11, 1904. New studies of the folding of the occipital sulci in human brain. Journ. of Anal, and Physiology, vol. 41, p. 198, 237.
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116 JAMES B. MURPHY
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from the point of view of their relations to the area striata. In the following points, which can be seen in fig. 1, Smith sharpens our definitions of the region (fig. 1-A.) The calcarine fissure, making the well-known stem of the Y, forms the limiting anterior boundary of the area striata in most human brains, which agrees with the findings of both Flechsig^ and Campbell.* Its corresponds to the calcar avis and is primitive in type. Its development corresponds to the differentiation of the cortex of the area (fig. 1-B.) The continuation of the calcarine fissure, namely, the retrocalcarine sulcus, is to be defined as a sulcus within the area striata, not bounding it, and the foldings of the area striata into retrocalcarine sulci is subject to great variations (fig. 1-C). The retrocalcarine sulcus usually extends around the occipital pole from the mesial surface to the lateral surface. This extension has been well-named by Cunningham, the external calcarine sulcus. Likewise, the area striata, surrounding this external calcarine sulcus, extends around the pole of the occipital lobe to the lateral surface of the brain and usually comes into relation to a curved sulcus, which Smith calls the lunatus, thehomologueof the Affenspalte.
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This study was begun to test the relation of the area striata to the sulcus lunatus, which it will be seen is a reaching out toward comparing the histological structure of different brains. The number of brains studied has been extremely small, but since the work is unavoidably interrupted for a few years, it was deemed best to publish the results that have been obtained.
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The sulcus lunatus Professor Smith considers definitely related to the area striata. To quote his words: *' In all mammals (with the exception of man in some cases) the stripe of Gennari extends to the lateral aspect of the hemisphere. In apes, and in most cases in man also, the anterior crescentic edge of this area striata pushes itself forward in such a manner that a deep cleft, a simple sulcus or a mere pucker is formed in front of the advancing
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' Flechsig. Ueber Untersuchungs-methoden der Grosshirnrinde. Berichte math-phys. Klasse d. K. Sachs. Gesellschaft, Leipzig, 1904, and Arch. f. Anat. u. Phys., Anat. Abt. 1905.
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('ampbcU. The Localization of cerebral function. Cambridge University
 +
Press.
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edges, like a trough in front of a wave. This trough is often bridged by one or several folds separating the deeper parts one from the other .... The sulcus lunatus is a depression formed by the forward projection of the cortical area containing the striata of Gennari/' It is found in many forms and positions on the surface of the brain.
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The material for this work was selected at random from the collection in the anatomical department of the Johns Hopkins University. The drawings were made and the area striata was plotted before the records of the race were looked up, in all but one or two cases in which brains were chosen to even up the series, so as to rule out the personal equation as much as possible. There were however no records kept in the department to show the type of negro, whether full-blooded or mulatto. The drawings are geometrical tracings, made by means of the very accurate projecting apparatus made by Hermann of Zurich. Great care was taken to get the brains in as uniform a position as possible. In plotting the area striata, very thin sections were made with a razor, perpendicular to the surface of the cortex and extending just through the gray matter, after the manner Smith describes. My experience agrees with Professor Smithes in regard to the definiteness with which the area striata can be marked out with the naked eye (see Journ, of Anat. and Phys,, vol. 41, p. 240). I have not controlled the findings with Weigert sections. Starting with the anterior calcarine region and working back through the posterior and external calcarine sulci, these sections were taken at regular intervals, plotted and replaced in order to keep the brain intact. Except in a few poorly preserved brains, the stripe of Gennari showed up so distinctly that there was little trouble in making it out.
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The type of the drawings made is shown in fig. 1 . The mesial surface of the two slides was carefully drawn by the projection apparatus, then the lobes fitted together, and a third tracing of the sulci was made, looking directly own on the occipital pole, The circle in fig. 1-B shows the area used in the other illustrations. The shaded region is that part of the cortex bearing the stripe of Gennari. The mesial surface drawings of the other brains are not shown, as the extent in the two races is practically the same.
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118 JAMES B. MURPHY
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In studying the series of ten negro brains (figs. 1 to 10) certain points are readily seen in the drawings. First, as Smith pointed out, there is a great variation both in the extent of the area striata on the lateral surface of the brain and in its relation to the sulcus lunatus. The sulcus lunatus tends to be more definite on the left side than on the tight (see figs. 7 and 8). As was noted by Smith, the area may touch the sulcus, but more often does not quite reach it. In the series of ten negro brains, there is a definite lunatus making an anterior boundary for the area striata on the left side in eight cases, and a doubtful one in two (figs. 3 and 9). In fig. 3 the limiting sulcus (X) is slightly farther from the area striata; while in fig. 9 it is very small. On the right side there is a definite lunatus in three brains, figs., 1, 4 and 6, a possible one in four, figs. 2, 5, 9, and 10, while in three, figs. 3, 7 and 8, no definite lunatus in made out. Fig. 10 is from a mulatto.
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In the series of six white brains, the area striata on the lateral surface is somewhat less extensive than in the negro series. The presence of a sulcus lunatus is certainly not as marked as in the other series. In one brain (fig. 16), it is very definite on the right side, and is probaly present in the left, and it is interesting to note that this is the brain of an undersized man, who from the statements of the hospital history was probably a degenerate. In this case the striated area is much more extensive than in the other white brains. All of the rest must be regarded as having a most indefinite lunatus or none. The unbroken extension of the posterior calcarine sulcus to the lateral surface, though present in several instances at least on one side, is less often noted than in the negro series. There are in several instances crescentic folds in these white brains which might possibly be considered the lunatus. I have not so classified them because they are some distance from the area and bear no constant relation to it and hence, in my judgment, should not be classed as the sulcus lunatus.
 +
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Duckworth,* in his article on the brains of aboriginal natives of Australia, found that the retrocalcarine sulcus was continued to the lateral aspect of the hemisphere in 37.5 per cent of the cases^
 +
 +
■ Duckworth. Brains of the aboriginal natives of Australia. Journ Anat, and Phys.f January, 1909.
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SULCUS LUNATUS IN NEGRO AND WHITE BRAINS 119
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This extension he regards as a simian characteristic. He finds it occurs much more often on the left side than on the right. The simian sulcus, occipitalis lunatus, is more frequently found on this side also. These same facts have been observed in my series of negro brains.
 +
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From this limited series it would seem that the sulcus lunatus is often the anterior limit of the visual cortex on the lateral surface of the brain but cannot be regarded as nearly so constant as the relations of the calcarine fissure and retrocalcarine sulcus In contrasting the two series for racial distinctions, while it is true that the negro series shows a tendency to a more marked lunatus, it cannot be regarded as a racial characteristic since there are negro brains without it, and a white brain with a definite lunatus. This study however, confirms Smithes idea that the above method brings out the variations in the visual area, which, whether racial or individual, it is worth while to investigate.
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Fig. 6
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Fig. 7
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r.c
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Fig. 1. Tracings of the occipital lobe showing the area striata (shaded) both on the mesial and lateral surfaces. Brain of a negro (Col. No. 3027).
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F. C, fissura calcarina; S. R. C. sulcus retrocalcarinus; S. C. E., sulcus calcarinus externus; S. L., sulcus lunatus.
 +
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Figs. 2 to 10. Tracings of the occipital pole of negro brains, showing the area striata on the lateral surface.
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S. L. sulcus lunatus; X, a possible sulcus lunatus.
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Fig. 9
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Fig. 10
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Fig. 12
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Flg.13
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Ra.i5
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Fig. 16
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FiG8. 11 to 16. Tracings of the occipital pole of white brains, showing the area striata on the lateral surface. S. L., sulcus lunatus.
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==THE HISTOLOGY OF THE NASAL MUCOUS MEMBRANE OF THE PIG==
 +
 +
NATHANIEL ALCOCK
 +
 +
From the Zodlogical LaborcUory of Northwestern University
 +
 +
WITH FIFTEEN FIGURES
 +
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With the introduction of the methylene blue and the Golgi methods there began a new era of investigating nervous tissues. When these methods were applied to the histology of the nasal mucous membrane, they made clear for the first time the connection of undoubted olfactory fibers with the sensory cells. Prior to the use of these methods a number of interesting observations on the structure of the nasal epithelium had been made — extending, in fact, over a period of thirty years — ^but the results obtained have been largely superseded by later investigations.
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The pioneer group of researches upon the nasal mucous membrane includes the work of Eckhard ('55), Ecker ('55), Max Schultze ('56, '62), Exner ('72), Cisoflf ('74), and von Brunn ('75, '80).
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 +
The papers of this period worthy of greatest consideration are those of Max Schultze. In 1856^ he made the first good analysis of the histology of the nasal mucous membrane, observing all classes of vertebrates and giving sketches of two kinds of cells in the pike, frog, owl and man. His figures were so good that two of them (of frog and man) have been frequently republished.
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The two kinds of cells that he designated are (a) six-sided prismatic supporting elements — non-ciliated in the olfactory region, but ciliated in the respiratory region, and (6) true olfactory cells with a large body, a slender peripheral process, and very fine central process showing varicosities. He was the first to claim that the olfactory cells were the only percipient elements of the sense of smell. He supposed their central
 +
 +
Contribution from the Zoological Laboratory of Northwestern University
 +
under the direction of William A. Locy.
 +
 +
Monatsber. d. K, Preuss. Akad. d. Wiss. zu Berlin, November, 1856. Pp.
 +
504-514.
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fibers were the true olfactory fibers but was unable to trace them to the olfactory bulb. He found olfactory hairs on the sensory cells of the frog but not on those of mammals. He also saw stellate cells which he likened to the ganglionic cells of the retina. His paper of 1862' of ninetyfour pages and five lithographed plates is an extension of his earlier observations and embraces observations on all classes of vertebrates.
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It was in 1886 that Ehrlich published his paper on the methylene blue method and described its reaction toward several types of nerve-cells, among them the olfactory sensory-cells. He described these briefly, paying special attention to the central processes of the cells which he observed passing downwards between the central processes of tiie supporting cells into the submucosa and there being continued as the small fibers of the olfactory nerve. This was an ocular demonstration of the connection that Max Schultze had assumed to exist. The foUo^dng year Arnstein, employing the same method, published a paper in which he described the connection of the olfactory cells with the olfactory nerve and thus agreed with Ehrlich.
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In 1887,* Dogiel published the results of his work on the olfactory organ of ganoids, teleosts, and amphibians. His observations indicate a polymorphism of sensory cells of the olfactory membrane. He described three types which have been seen by several other observers (Morrill, '98; Jagodowski, '01).
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The observations of Grassi and Castronovo^ in 1889 by the application of the Golgi method to the olfactory membrane of the dog, strengthened the conclusion that the fibers of the olfactory nerve are connected directly with the nerve-cells of the olfactory membrane. They described the true olfactory cell and also a fine varicose central process descending in a curved course to the subepithelium and there uniting with similar fibers to form the olfactory nerve. They also mentioned free nerve endings in the nasal mucous membrane. They observed no anastomosis of nerve processes although they did show in their figures and described in their text one case where two sensory cells were connected by one fiber. They held that the supporting cells were not connected with the nerve fibers. They described the histology of the three areas of the olfactory membrane, giving particular attention to the boundary or intermediate zone, concluding that in the adult it exhibited the embryonic characteristics of the true olfactory region.
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» Arch. f. Mik, Anal. Bd. 27, 1886.
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Ahhandl d. Naturf. Gesellsch. zu Halle. Bd. 7.
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» Arch, f, Mik. Anat. Bd. 34, 1889. Pp. 385-390.
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It will be noted that up to this time investigators had generally supposed that the direction of growth of olfactory nerve fibers was outward from the brain to the olfactory membrane. In the year 1889 this conception was materially changed through the work of William His on the development of nerve fibers and also through that of Ramon y Cajal. The latter traced fibers of the olfactory nerve to the bulbus olfactorius and there found them terminating in brush-like ends that commingle with the dendrites of the mitral cells and form the olfactory glomeruli. He concluded therefore that the sensory cells in the olfactory membrane are the cell bodies from which fibers of the olfactory nerve arise, and that the fibers of this nerve grow not from the brain to the membrane, but the reverse.
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The occurrence of free nerve endings in the olfactory membrane was indicated by Cajal. He gives a sketch showing free nerve endings between the cells of the olfactory membrane. Von Lenhoss^k observed similar appearances and concluded that they were terminations of the trigeminal nerve.
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The work of Van Gehuchten (*90) on the rabbit and that of Retzius (*92) on embryos of the mouse, cat, dog and rabbit and his further paper in 1894 on the fishes confirmed the work of previous investigators, adding certain details that do not require mention here.
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 +
Von Brunn's paper of 1892* dealing with the nasal membrane of the human body is of especial interest. This observer had published two previous papers on the anatomy of the olfactory apparatus, one in 1875 (Dog, Cat, Rabbit, Sheep, Calf, Fish, Salamander) and another, in 1880 (Rabbit) on the same organ in the rabbit. The third paper (1892) dealt with the olfactory apparatus of man. He gives a complete analysis of the membrane, describing its extent, the different cells found, the limiting membrane (described in the three papers, but first mentioned by Sidky), the nasal cells and the connection of the nerve and the sensory element. On the peripheral ends of the olfactory cells he observed from six to eight short pointed hairs but was unable to say whether or not these were normal structures or artefacts. However, he thought them to be normal structures. He concluded also that the nerve fibers are in connection with the sensory-cells only, and not with the supporting elements.
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Jagodowski^ in 1901, published observations on the olfactory organ
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• Arch. f. Mik. Anat. Bd. 29, 1887. ' Anat. Am. Bd. 19, 1901.
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126 NATHANIEL ALCOCK
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of the pike. He described three types of sensory elements corresponding to those mentioned by Dogiel. The types are (a) cylindrical Riechzdlen of Max Schultze with slender peripheral processes, (6) Riechstdbchen. with peripheral processes as thick as the cell-body, and (c) Riechzapferiy short cells, near the outer border of the mucosa and lacking a peripheral process. This polymorphic condition of olfactory cells has been observed by Morrill ('98, Selachians) and Grassi and Castronovo have pictured a cell like the Zapfen in the olfactory membrane of the dog. He also described a new structure, the smell whips. According to Jagodowski each type of olfactory cell bears on the peripheral end a long slender whip-like process which extends into the nasal cavity. He also saw free nerve endings.
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Ballowitz^, in 1904, published observations on Petromyzon fluviatilis, which corroborated the work of Retzius (1880), also on petromyaon. He found but one kind of sensory elements and no transitional forms. According to his observations the olfactory cells are of one type but vary in length according to the position of their nuclei in the membrane. On their peripheral ends he saw 10 to 12 fine pointed hairs which are beautifully represented in his sketches. He observed cilia on the supporting cells.
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Work on the development of the nervous elements of the olfactory membrane, such as that of Disse* ('96) and Bedford^® C04), shows conclusively that the neuroblasts of the olfactory nerve fibers are located within the membrane, and that the nerve fibers grow from the nerve cells toward the brain.
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 +
Miss Read's" "Contribution to the Knowledge of the Olfactory Apparatus in Dog, Cat and Man" ('08), embraces the study of the gross anatomy of the olfactory nerve, as well as a description of the histological structure of the olfactory epithelium illustrated by many figures. Her work also includes a study of the organon vomero-nasale. Her sketches of the sensory-cells of the cat, stained with methylene blue, show the character of these cells very well. She found free nerve terminations in the olfactory membrane, which she regards as derivatives of the trigeminal nerve. She determined that there is no anastomosis of the nerve fibers, but that they preserve their individuality from the nasal epithelium until they terminate in the glomeruli of the
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« Arch. f. Mik. Anat. Bd.64, 1904.
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Marburg. SiUungsbr.j October, 1896.
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^^ Jour. Com-p, Neurol, and Psychol.^ vol. xiv, 1904.
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" Am. Jour. Anat. May, 1908.
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olfactory bulb. She finds in the epithelium of the organon vomeronasale cells apparently identical with the sensory-cells of the olfactory mucosa.
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More extended reviews of literature are found in Disse {Ergeb. d. Anat, u. ErUmckLf Bd. 11, 1901), Jagodowski (AnaL Anz,y 1901), and Miss Read (Am. Jour. AnaLy May, 1908). The last mentioned paper was not available until I had completed my work.
 +
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OBSERVATIONS
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The observations, the results of which follow, were undertaken with a view to supplying a purely objective account of the form of the various cellular elements entering into the composition of the nasal mucous membrane, and to determine their normal arrangement. The work was begun in September, 1906, in the Zoological Laboratory of Northwestern University, and was carried on for two years. From the beginning it has been under the direction of Prof. WiUiam A. Locy, whom I wish to thank for assistance in the observations and preparation of the manuscript. Observations were begun on the rabbit, but by comparison the nasal mucous membrane of the pig was found to give better pictures of the cellular elements, and the present account is confined to descriptions of pig material. I also had for comparison a large series of sections of the nasal-mucous membrane of the rabbit made by Miss Caroline Jaycox.
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The pig material used consisted of embryos from six to twelve inches long obtained from the uterus of the parent about thirty minutes after the latter had been killed. In all cases the young specimens were found alive and in good condition. After removal from the uterus the head of the embryo was severed from the body, and split into halves. The nasal cavity was opened by cutting away the septum, and either the wholfe placed in the fixing or macerating fluid or the turbinal bones removed and placed in the desired Uquid.
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Two general methods have been followed: That of maceration and that of the study of sections.
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Several of the standard macerating fluids were employed. It was found, however, that 25 per cent to 30 per cent alcohol gave
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128 NATHANIEL ALCOCK
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good results with this material. The pieces of tissue were placed in the Uquid for a period of thirty-six to forty-eight hours and in a few cases good results were obtained from material which had remained in the alcohol from seventy-two to ninety-six hours. The length of time necessary varies with the age of the pig. The pieces were then transferred whole to a solution of equal parts of 50 per cent alcohol and glycerine in which they were first teased with needles and then shaken vigorously in small bottles. In the majority of cases the cells were found floating free and in clusters in the Uquid. To the solution containing the isolated cells were added a few drops of picro-carmine which, in a few hours, stained the cells very satisfactorily. A few drops of this material was then mounted and the coverslip sealed with glycerine jelly and gold-size cement.
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For fixing fluids Van Gehuchten^s, Miiller's, 5 per cent formalin, formalin-acetic, corrosive-acetic, picro-sulphuric, and Zenker's were used. The best results came from the fixation by the Zenker solution. For relatively thick sections the pieces of material were imbedded in celloidin and for thinner sections paraflSn was used. The most conunon and best stains used were iron alum and haematoxylin, and eosin and Delafield's haematoxylin. The sections range from three to eight microns in thickness.
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 +
The larger celloidin sections, after imbedding, were decalcified in 5 per cent nitric acid for twenty-four hours.
 +
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In the pig there are five chief ethmo turbinal folds each of which is lobulated. The arrangement exhibited in Fig. 1, which is a drawing of a section cut in a plane perpendicular to the long axis of these folds of a pig embryo twelve inches long, is as foUows: The five main folds (F 1, 2, 3, 4, 5) each have a cartilage supporting tissue covered with a relatively thick epithelium. Each fold, with the exception of the second, extends to the side wall of the cavity. The lateral surfaces of the several main folds are elevated into ridges which run horizontally. The first main fold shows 12 of these ridges. The second, which seems to be a division of the first, 8; the third, 11; the fourth, 7; the fifth, 4. Between the second and third main folds are two smaller ones (F 6 and 7) ; between the third and fourth and between the fourth and fifth are also seen smaller folds (F 8, 9).
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In fresh material of the stages examined the epithelium of the nasal cavity is apparently of uniform color. It was not possible to distinguish areas of a yellowish tint indicating the distribution of the olfactory cells, as has been observed in many vertebrates.
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The epitheUum in fresh condition is so tender that it is almost impossible to remove it from the cartilage upon which it lies, but after fixation with Zenker's fluid this can easily be done even from the turbinal folds. However, it was found that the epithelium of these folds could best be sectioned by leaving it attached to the cartilage and dividing the entire piece into six to eight blocks.
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As there is no easily discernible color variation in the different parts of the nasal mucous membrane of pigs of this age, the different areas can be distinguished only by a study of their finer anatomy. On the basis of the thickness of the epithelium and of its component elements two regions can easily be distinguished. One, designated by the earlier investigators as the respiratory region, includes the epithelium of the outer side, the upper, and the lower walls of the nasal cavity and certain parts of the turbinal folds and of the septum. The second, the olfactory region, embraces the sensory epithelium found on the turbinal folds and parts of the septum. My study of its structure was limited to that part on the ethmo-turbinal folds. A third area, the intermediate zone, described at length by Grassi and Castronovo in the dog, can be distinguished in the pig.
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Respiratory Region. The epithelium of the respiratory region (Fig. 2) is from .037 to .041 mm. in thickness, It is composed of two kinds of cells, cylindrical epithelial cells {Sup, C) and the basal cells {Bas. C). The cylindrical cells (see also Fig. 3) extend across the epithelium from the free surface to the basement membrane. Their large oval nuclei he a httle above the middle horizontal plane of the section. The majority of them show a large oval nucleolus. The peripheral process of each cell extends to the surface where it expands slightly into a dome-shaped disc above the limiting membrane. On this disc are found fifteen to twenty-five slender hairs (CiL) which average about .0065 mm. in length. The central process {Cen, Pr.) of each cylindrical
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130 NATHANIEL ALCOCK
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cell extends from the region of the nucleus almost to a pointed end which rests on the basement membrane. These cells show no branching or forking. In the spaces between the pointed ends are the basal cells (Bos. C.) which are conical in shape with their large bases turned toward the basement membrane. The nuclei of the latter are spherical.
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The sub-mucosa of this respiratory region is from two to three times the thickness of the epitheUum itself. It is made up of loose elastic connective tissue and in it are to be seen numerous blood vessels and many of Bowman's glands.
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Olfactory Region, (a) The Supporting Elements. The olfactory membrane, containing the sensory nervous elements, is confined to the epithelium of the turbinal folds. It has been found on all five of the folds, both on the surface exposed to the nasal cavity and on the lateral surfaces as well. The sensory olfactory membrane varies in thickness from .062 to .07 mm. It is composed of three types of cellular elements, namely, two kinds of supporting elements and the sensory cells. The supporting elements are the cylindrical cells (Figs. 4,10, 11,12) and the basal cells (Fig. 12, Bos. C.) The latter are similar to those found in the respiratory region. The cyUndrical cells are different from those of the respiratory area. Their nuclei which, like those already described, are large and oval, he in a plane near the limiting membrane, relatively higher in position than those of the supporting cells of the respiratory region. These nuclei stain very deeply with iron haematoxylin and also with haematoxyUn and eosin (Figs. 10, and 11, Sup, C.) The peripheral portion of these cells extends to the limiting membrane in a thick process nearly as wide as the cell in the region of the nucleus. The supporting cells in the olfactory region of the pig do not possess cilia. The central process is fine, frequently branched, or forked (Fig. 4), and extends to the basement membrane. Between the forks of the supporting cells are the basal cells in the same relative position as they are in the respiratory area. In no case, neither in the sectioned material nor in the macerated preparations, has a nerve fiber been seen in connection with a supporting cell.
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Olfactory Region . (6) The Sensory Cells. The sensory elements of this region, isolated by maceration, are shown in Figs. 5, 6, 7, 8, 9, and in normal position in the membrane in Figs. 10, 11, and 12. As these figures show, the olfactory cells arebi-polar elements, the large oval cell body, which contains a nucleus of nearly the same shape, giving rise to a central and a peripheral process. The olfactory cell bodies lie at varying levels in the epitheUum below the plane of the nuclei of the supporting cells. In the lower half of the cell body is the large ellipsoidal nucleus which, with iron alum and haematoxylin, does not stain quite so deeply as the nuclei of the supporting cells. The peripheral process arises from the tip of a conical mass of cytoplasm which makes up the upper half of the cell body. This process varies in length in different cells, depending of course upon the position of the cell body within the membrane. The diameter of the process varies from one-fifth to one-third that of the cell body, and extends to the surface and passes through the limiting membrane enlarging in this region into a knob (Kn.) whose diameter is one and one-half to two times that of the process itself. On this knob are to be seen four to eight hair-like processes, extending above the knob into the cavity of the nose. In both the macerated material and in the sections the olfactory hairs vary in length from .008 to .001 min., or a trifle longer than the cilia of the supporting cells of the respiratory region. Unlike the latter they are thick and instead of being pointed are not only blunt but in some cases they seem to have more or less thickened ends. In the sections stained with iron alum and haematoxylin and in the macerated material stained with picro-carmine, the bases of these cilia, which are equatorially arranged around the knob of the process, are stained very deeply and look like small dots. It is possible to see olfactory hairs in all sections where the knobs are shown, but in the macerated material they do not occur so frequently and in a great many cases are broken off. Where these hairs do not show, however, the small dots representing the bases of them, can easily be seen. This absence of olfactory hairs from so many of the sensory elements in macerated material may be explained by the treatment which the cells received in being separated. I conclude that the olfactory hairs are normal structures and not artefacts.
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132 NATHANIEL ALCOCK
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At different levels along the peripheral processes of the olfactory cells occur slight enlargements (Figs. 6, 7, 8). These show best in the isolated cells. As many as two have been seen on the same cell. Similar enlargements are shown in the figures of Max Schultze (1856, 1862) and in those of Von Brunn (1892).
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Below the nucleus of the sensory cell the cytoplasm is drawn directly to a point which in the majority of the cells is in a line with the long central axis of the cell body, but sometimes it is found to one side of it. From this point emerges a long, slender, varicose fiber, {Cen, Pr.), which extends downward in a curved or wavy course toward the sub-mucosa passing between the feet of the supporting cells. It passes through the basement membrane into the sub-mucosa and there is lost in the connective tissue. In the sub-mucosa several of these fine fibers come together to form the smaller branches of the olfactory nerve, but the fibers do not anastomose. In the macerated preparations the cells possess only a very short fiber, and often none at all. By maceration, the central processes, hke the olfactory hairs, are easily broken off.
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In the sectioned material as well as in the macerated preparations have been seen oval cell bodies, possessing varicose nerve fibers like those of the sensory elements just described, but having no peripheral processes (Figs. 10, 11, 12). In the case of the sections it is plain that this appearance is due to the fact that the plane of the section does not pass through the peripheral process but only through the cell body. In Fig. 15Ais shown the cell body of such an element and in Fig. 15B is shown the same region of the next section to it and in it is seen the peripheral process of the sensory cell (Per. Pr.), whose body in Fig. 15 A might be mistaken for a uni-polar element. Many similar cases have been examined and in all but a very few it was possible to find in the neighboring sections the missing peripheral processes. In like cases in the macerated material it could sometimes be seen that the process had been broken off in the maceration. There is not enough evidence from my observations to justifj'^ the separation of the sensory cells into the two classes of uni-polar and bi-polar elements. It appears that they are all bi-polar.
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THE NASAL MUCOUS MEMBRANE OF THE PIG 133
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The sub-mucosa of this region resembles that of the respiratory area except that it is much thicker and contains a greater number of Bowman's glands.
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Fig. 9 shows the peripheral end of an olfactory cell broken away from its cell body and bearing eight olfactory hairs.
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Figs. 10, 11 and 12 represent camera drawings of sections showing the various histological elements of the mucosa in their natural position. It is to be noted that the knob-like endings of the peripheral processes are situated in front of the limiting membrane. They are large and the olfactory hairs are long.
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Fig. 13 shows a sensory cell in section with its nucleus near the basement membrane, and, consequently, a very long peripheral process.
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The results obtained indicate the success of Zenker's fluid followed by iron haematoxylin staining. An examination of the published drawings of the histology of the nasal membrane will show that it is infrequent to find the knob-like eminences and the olfactory hairs so well exhibited as in the pig material upon which the above observations are based. The sketches that show the hairs best developed are those of Ballowitz^^ j^ Petromyzon.
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The Intermediate Zone. This zone lies between the two regions just described and exhibits the characteristics of each. It is the shading of the one into the other. It is thinner than the olfactory region, and thicker than the respiratory. Besides the sensory elements it possesses supporting cells of three types. Of the latter the basal cells are similar to those of the other two regions. The long supporting cells proper can be divided into two classes on the basis of possessing or lacking cilia. Those that do bear cilia (Fig. 14, Sup. C. — are very similar to the supporting elements of the respiratory area. They extend across the full width of the membrane and their central processes are pointed and rest upon the basement membrane. The other supporting elements lack cilia, and in this regard are like those of the olfactory region, but their central processes do not appear to be forked.
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The sensory elements of this region are not as long as those
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" Archiv, /. Mik, AnaL Bd. 64, 1904.
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134 NATHANIEL ALCOCK
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of the olfactory area, and are fewer in number. In the well diflferentiated olfactory region about 70 per cent of the cells appear to be nerve elements, while in the middle of the intermediate zone about the same percentage of the elements are supporting cells. The nerve cells of this zone become more and more scattered as the respiratory region is approached.
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A diflferential count of the isolated cells from the entire turbinal membrane shows that 49 per cent are olfactory elements.
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SUMMARY. The facts of observation briefly summarized are as follows:
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1. The nasal mucous membrane of the pig is divided into three areas: The olfactory, characterized by the predominance of sensory cells; the respiratory region, characterized by the absence of sensory cells and the presence of ciliated supporting cells; and, third, the intermediate zone, characterized by the presence of a small number of sensory cells and both cihated and unciUated supporting cells.
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2. There are supporting cells of three easily distinguishable types, viz: the unciliated of the olfactory region; the ciliated of the respiratory region; and the basal cells conunon to the three regions. Besides these there are the ciliated cells of the intermediate region which difl'er slightly from those of the respiratory area, and also, the unciliated supporting elements of the intermediate zone which are not identical with those of the olfactory region. •
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3. The sensory cells so far as observed are of one type, bi-polar. The peripheral process is slender and on its free endns a knob bearing five to eight hair-like processes. The nerve fiber passing centrally, is fine and beset with varicosities. The fibers unite to make up the bundles of the olfactory nerve.
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4. No connection has been observed between nerve fibers and the supporting elements of any area.
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EXPLANATION OF FIGURES
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Fig. 1. Section of the ethmo-turbinal folds of a pig embryo 12 inches long.
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The section is cut in a plane perpendicular to the long axis of the folds.
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Fig. 2. Section through the respiratory region of the second turbinal fold of a pig 11 in. long. Bas. C, basal cell; Ct7., Cilia; Cen. Pr.y central process; Nu.y nucleus; Sup. C.y supporting cell.
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Fig. 3. Isolated supporting cell of the respiratory region macerated in 25 per cent alcohol.
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Fig. 4. Single supporting cell from the olfactory region of the pig. L. 3/., limiting membrane; Nu., nucleus; Cen. Pr., central process.
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Figs. 5, 6, 7, 8. Sensory cells from the olfactory membrane of the pig drawn to the same scale. Showing variations in the length of the peripheral process. Cen. Pr., central process or nerve fiber; Kn., olfactory knob; Nu., nucleus; Olf. H., olfactory hair, Per. Pr., peripheral process.
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Fig. 9. Peripheral end of an olfactory cell bearing eight olfactory hairs.
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Fig. 10. Section through the olfactory membrane of a pig embryo 61 in. long. From the second ethmo-turbinal fold. Olf. H., olfactory hairs; Kn., terminal knob of olfactory cell; Olf. C, olfactory cell; Nu., nucleus; Cen. Pr., central process or nerve fiber; Bas. C, basal cell; Bas. Mem., basement membrane.
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Fig. 11. Olfactory membrane of the lateral surface of the first ethmo-turbinal fold of a pig embryo 6} in. long. Reference letters same as in Fig. 10.
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Fig. 12. Olfactory membrane from the same specimen and the same fold as in Fig. 11; Lim. Mem., Limiting membrane.
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Fig. 13. Section through the olfactory membrane of a pig embryo GJ in. long, showing one olfactory cell with a very long peripheral process. >i
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Fig. 14. Section of the olfactory membrane in the intermediate zone from the first ethmo-turbinal fold of a pig embryo 6J in. long.
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Fig. 15 A. Section through the intermediate zone of the olfactory membrane from the first ethmo-turbinal fold of a pig embryo 6i in. long.
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Fig. 15 B. Adjacent section to that shown in A. Shows the peripheral process of the chief olfactory cell the body of which is shown in the previous section.
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==A SIMPLE ELECTRIC HEATER AND THERMO-REGULATOR FOR PARAFFIN OVENS, INCUBATORS, ETC==
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C. M. JACKSON
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From the Anatomical Laboratory, University of Missouri ^ Columbia
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It is evident that for laboratory apparatus electric heating is in most respects far superior to gas heating, on account of its greater convenience and safety. The latter consideration, that of safety, applies with special importance to those appliances which require continuous heating, and which are left for considerable periods of time without supervision. Those of most importance in biological laboratories are incubators, drying ovens, and paraffin ovens. Experience has shown the danger of fires where gas burners are used for this purpose, even when every reasonable precaution is taken;
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For some time, therefore, I have been working on the problem of replacing the gas burners with electric heaters. Various electric appliances for this purpose have been put upon the market, but they are as yet used only to a very limited extent. The chief difficulty seems to be on account of the complexity and cost of the devices now available for electric heaters and thermo-regulators. For example, those now on the market for use with paraffin ovens and incubators cost from $25 to $100 or more. An electric heater and thermo-regulator which is simple, efficient and cheap should displace the gas burner in every laboratory.
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In such an apparatus we have to consider (1) the heating mechanism; and (2) the thermo-regulator.
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(1) For heating purposes, I have adopted the incandescent lamps ordinarily used for lighting purposes. When placed under the oven in a case properly insulated, the light is converted entirely into heat, making a very effective heating apparatus. The cost of operation varies from one-half cent to one cent per hour for each 16 c.p. lamp. For a small oven, or for a comparatively low temperature, one such lamp is sufficient. For a par
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140 C. M. JACKSON
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affin oven (water jacket) 12 x 10 x 12 inches, I find that three 16 c.p. lamps will maintain a temperature of 55° to 60° C, which is sufficient for paraffin embedding. Incidentally it may be noted that the ordinary copper ovens radiate heat excessively, and are greatly improved by gluing a layer of asbestos paper over the outer surface.
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The case I am using is made of hard wood, lined with asbestos board one-half inch thick (fig. 1 ) . The asbestos board may be procure'd from the H. W. Johns-Manville Company, New York, or from their branch houses in all the large cities.
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The principal objection to the use of the ordinary incandescent lamps is that the carbon filaments burn out somewhat more rapidly than usual, on account of the high temperature. This difficulty is easily avoided by using lamps designed for a higher voltage than is used in the circuit for lighting purposes. If 110 volts are used for lighting, lamps of 125 volts may be used for heating. These would not be suitable for lighting, but are almost as effective for heating, and far more durable, being practically indestructible.
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Another objection may arise in cases where the electric current is not available continuously. In our laboratories, for example, the current suppUed by the University plant is off from midnight to 5 a.m. This might be a fatal defect with incubators for some purposes, but for paraffin embedding it offers no serious disadvantage. Objects are rarely left in the melted paraffin over night, and even when they are, no harm is done by temporary cooling down of the oven. Before 9 o'clock in the morning the oven is re-heated ready for use. In a drying oven likewise the only disadvantage is the loss of a few hours of maximum temperature.
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(2) In order to regulate the temperature, the incandescent lamps are placed in two parallel circuits. In the first circuit is one lamp (or more, if required) of sufficient size (c.p.) to heat the oven up to a point slightly below the temperature which it is desired to maintain. In the second circuit is another lamp which, together with the first, will heat the oven to a temperature slightly higher than that desired. The second circuit, however, is connected with a thermo-regulator placed inside the oven and adjusted so that
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A SIMPLE ELECTRIC HEATER AND THERMO-REGULATOR 141
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Fig. 1. Diagram of a vertical section showing arrangement of electric heater and thermo-regulator.
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A, wall of oven or incubator, resting upon the heater. B, the inner case of the heater, a box made of asbestos board one-half inch thick, and joined together with screws. Cracks and irregularities may be filled with asbestos paste. The outer case, C, is made of oak seven-eighth inch thick. The floor of the outer case is one-half inch thick, and is fastened with screws so as to be easily removable. The inner case rests upon screw-eyes which extend into the walls of the outer case. Between the floors of the cases a space one-half inch deep is left for the wiring. The external measurements of the outer case should correspond in length and width to those of the oven which it supports. The depth of the inner case should be 6 inches, inside measurement, so as to give room for a 16 c.p. lamp, placed upright in a receptacle as indicated in the figure at E and F. For an oven 12 x 10 xl2 inches, to be heated to 60** C, four receptacles should be provided, three to be connected directly in circuit, and one connected by the wiring (J) in series with the thermo-regulator, K, placed inside the oven. A switch, I, snould be provided for the latter circuit, and another for the other circuit. G represents the wire, connecting with the source of supply, with attachment plug at H.
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142 C. M. JACKSON
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when the desu-ed temperature is reached the circuit is broken, being reestabhshed when the temperature drops slightly.
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Various forms of regulators have been invented which can be used for this purpose, all depending upon the varying expansion of substances at different temperatures to make and break the circuit. These regulators may be divided into two classes. In the first, or liquid type, a float rests upon a column of mercury or other liquid. This type is desirable where extreme accuracy of regulation is necessary; but otherwise it is undesirable on account of its cost, complexity, and liability to get out of order. The second class is constructed entirely of solid metal, the contact being made and broken by the varyiilg expansion of a metallic band. While not quite so delicate as the first type, the metallic type is sufficiently accurate for all ordinary purposes. It has the great advantage of simplicity and durability, with nothing to wear out or get out of order. The thermo-regulator which I have adapted for present purposes consists essentially of a coiled steel band, with platinum contact points and is taken from an apparatus used to regulate the heating of rooms. It is manufactured by the Johnson Service Co., of Milwaukee, Wise, and is quoted by them at $5, which, however, includes an outer case, thermometer, etc., in addition to the thermostat proper, (which is all that is needed). A number of these thermostats second-hand, but in good condition, can be supplied by Mr. J. A. Whitlow, Heat and Light Station, University of Missouri, Columbia, Mo., at $2 each. At this rate, the cost of the whole apparatus for heating and regulating an ordinary oven would be less than $10.
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It is important to bear in mind that this thermo-regulator should not be placed in a circuit of more than one-half ampere (one 16 c.p. lamp) on account of burning out the contact points, and also because the weaker the current, the more accurate the regulation. With an 8 c.p. lamp, at ordinary room temperatures,the variation is usually less than l^C. from the point set.
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In case a thermo-regulator of the kind mentioned is not available, one similar in type could readily be constructed. Another form of metallic thermo-regulator has recently been described by Abekenand Cuthbertson (U. S. Naval Medical Bulletin, vol. 4, no. 1, January, 1910).
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==THE EVOLUTION OF THE CEREBRAL CORTEX==
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J. B. JOHNSTON
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University of Minnesota WITH TWENTY FIGURES
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In the course of a general treatment of the nervous system of vertebrates, published in 1906, the writer stated briefly the results of personal investigations upon a number of topics. In some cases, it has since appeared, the brief treatment did not present adequately the evidence upon which the conclusions were based. Circumstances have greatly delayed the publication of this evidence in more complete form. Recent papers have treated with some fullness the mesencephalic root of the trigeminus, the origin of taste buds and the question of the boundary between diencephalon and telencephalon. The subject of the present paper is to be taken up in a series of short papers with the purpose of demonstrating the early stages in the phylogenetic history of the cerebral cortex. It is but just to say that the great bulk of the evidence now presented upon these various subjects was in hand before the book referred to was written.
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The boundary between diencephalon and telencephalon is marked by the velum transversum above and by the caudal surface of the chiasma-ridge below. The telencephalon consists of a ventral portion occupied by the optic chiasma and other decussating fibers and a dorsal portion comprising the corpus striatum, rhinencephalon, cortex, lamina terminalis, tela chorioidea, etc.
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The subject matter of this paper was presented at a joint meeting of the
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Chicago Neurological Society and the Biological Society of the University of Chicago, December 21, 1909, and to the American Association of Anatomists in Boston, 1909.
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Neurological studies from the Institute of Anatomy, University of Minnesota, No. 12.
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The ventral portion never enters into the evaginations by which the lateral lobes or '^hemispheres are formed. Of the dorsal portion only a part is evaginated in primitive vertebrates and successively more and more of the wall of the unpaired ventricle turns out to becomethe wall of the lateral ventricle in the higher classes of vertebrates. For reasons of practical convenience in description the distinction between evaginated and non-evaginated parts of the forebrain will be more often used than the more fundamental distinction between dorsal and ventral portions. It is necessary to have unambiguous terms to express this distinction, especially in view of the changes which take place from one class of vertebrates to another, resulting in the transformation or translocation of non-evaginated area into the evaginated. For the non-evaginated wall of the unpaired ventricle in all classes may be used the term telencephalon medium. I have suggested (1909) that the term hemisphere be used to include all that belongs to one-half of the telencephalon. If, on the contrary, it is desirable to retain for the hemisphere the boundaries given it in the BNA, namely the walls of the lateral ventricles in man, it should have the same significance in lower vertebrates. If this usage is adopted it must be clearly recognized that in various classes of lower vertebrates the term hemisphere will include Uttle or none of the cortical areas which predominate in the hemisphere of man. While the question of this usage is being settled, the term lateral lobes used by the older anatomists may be used for the evaginated portion of the forebrain without ambiguity.
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In median sagittal section of the embryonic forebrain (figs. 17-20), the roof begins at the preoptic recess and extends around the convex surface to the velum transversum. The median seam is the telencephalic part of the roof plate of His. About the middle of this is seen in many vertebrates a neuroporic recess, marking the point at which the neural tube remained longest in connection with the ectoderm. That part of the roof plate which lies between this point and the chiasma is known as the lamina terminalis; that part which extends from the recessus neuroporicus to the velum transversum is the lamina supraneuroporica. It should be emphasized that it is only for reasons of practical convenience that the lamina terminalis has been distinguished from the remainder of the roof plate, from which it does not differ in any important waj . The neural tube does not end forward in a wide opening whose dorsoventral diameter is measured by the lamina terminalis after the lateral walls are fused together. Rather, as the neural plate rolls
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Fig. 1. Schemata to illustrate the two conceptions of the lamina terminalis In all the sketches the neural tube is viewed from the left and a little in front. In A is represented the common view that the neural tube has a roof plate and a floor plate of equal length. The lamina terminalis is formed by the fusion of the side walls, lettered Hirnnaht of flis. The upper boundary of this would be marked by the neuroporic recess, the lower boundary by the optic chiasma. In B, C and D is illustrated the view stated in the text. The closing of the neural tube is retarded by its relation to the olfactory placode. There is fundamentally a smgle seam of closure, all of which belongs to the roof plate. The part of this seam between the olfactory nerve and the optic chiasma comes to have the appearance of an endplate (lamina terminalis) because of the forebrain flexure, and this 18 due to the influence of the olfactory nerve and its centers.
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Fig. 2. Sketch of the right half of the fore part of the brain of the sturgeon as seen from the medial surface. The primordium hippocampi is bounded below by the sulcus Monroi. The velum transversum is attached to the brain wall behind the so-called praethalamus.
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up the neural tube tapers to a point in the preoptic recess, and the lamina terminalis is the anterior part of the seam of closure along the mid-dorsal line (fig. 1). The conception of a *' frontal Hirnnahf of His is fundamentally wrong, but its convenience in descriptive anatomy has led to its continued use. The writer has at times inadvertently used or implied it, although he has held for some years the view here expressed. This view has been expressed by other workers also. The two views are incompatible and that of His is inconsistent with the facts of embryology and phylogenesis of the forebrain.
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It is necessary to define more exactly how the velum transversum indicates the boundary between the diencephalon and telencephalon. The velum is a transverse in-folding of the tela chorioidea and owing to the arched form of the membranous roof in most vertebrates the lateral borders of the velum may be compared to the pillars of an arch. Where these pillars of the velum nneet the lateral nervous walls of the brain in the embryo, these walls are indented by a vertical groove. This groove marks the boundary between the diencephalon and telencephalon. In the adult this boundary is marked by the attachment of the pillars of the velum to the massive lateral walls. In the brains of many fishes the arch of the velum is inclined forward so that the boundary line in question is not marked by the position of the velum in median sagittal section but by the place of attachment of the velum to the lateral wall. Fig. 2 shows what is meant in the case of the brain of the sturgeon, and the relations of the velum will be amply illustrated in the later papers of this series.
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The features of the telencephalon in which we are chiefly interested are (1) the degree of evagination of the lateral lobes and the functional areas contained in these in different classes of vertebrates; (2) the area from which the hippocampal formation of higher brains is derived ; (3) the area from which the general cortex is derived ; and (4) the morphological position and value of the palUal commissures. These features will be reviewed very briefly by the aid of simple schematic figures.
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The treatment of the cortex assumes the principle stated in a previous paper (1909, pp. 518-525) that the cortex develops from
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centers in primitive vertebrates which serve for the correlation of incoming impulses of different kinds. The cerebral cortex everywhere is nothing else than a complex of correlation centers.
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CYCLOSTOMES
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In cyclostomes the evagination carries out the formatio bulbaris and the secondary olfactory centers in larger part. Indirectly, owing to crowding from in front, the wall of the telencephalon medium is folded so as to enter into the caudal wall of the lateral lobe. This is a part of the region heretofore named '* striatum." It is not a proper part of the evagination and the folding spoken of accounts for the bifurcation of the lateral ventricle (fig. 4). The telencephalon medium includes secondary olfactory centers below and in front of the foramen interventriculare, so-called striatum below and behind the foramen, and primordium hippocampi (heretofore called epistriatum) above the foramen. (See figs. 3 and
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Fig. 3. Petyroinyzon dorsatus, late ammoca'les. Sketch of left half of fore part of brain to show functional areas in the telencephalon. The heavy broken line marks approximately the boundary between the telencephalon and diencephalon.
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Fig. 4. Petromyzon dorsatus, late ammoccetes. A, transverse section of telencephalon; By horizontal section, both through the foramen interventriculare. The broken line beneath som. area in B marks approximately the boundary between diencephalon and telencephalon. The region labeled somatic area has heretofore been called striatum.
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4.) That this primordium hippocampi belongs to the telencephalon and not to the diencephalon as held by Edinger, Sterzi, Tretjakoff and others is shown by the attachment of the velum transversum to the brain wall between this body and the ganglion habenulse. The primordium hippocampi presents certain definite histological characteristics which are constant in fishes and amphibians. It receives olfactory fibers of the second order by way of a decussation in the lamina supraneuroporica and receives ascending fibers from the hypothalamus, the tractus pallii. The hypothalamus is a tertiary visceral and gustatory center in other fishes and amphibians and may be supposed to have similar functions in cyclostomes. The entrance of the tracts mentioned into the primordium hippocampi constitutes it a correlating center for olfactory and visceral impulses. It would thus furnish the starting point for the differentiation of the hippocampus and may possibly contribute to the formation of other structures.
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The area called striatum is probably the beginning of the general or somatic cortex, but requires further investigation.
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Fig. 5. ^Scyllium stellarc, anterior part of the brain seen from above. The medial olfactory nuclei are very large, and the primordium hippocampi and anterior pallial commissure are carried far back. The line r.n.cxt. marks the dorsal opening to the sagittal fissure. The line v.ir. marks the point of attachment of the velum transversum.
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Fig. 6. Scyllium stellare, sketch of right half of fore part of brain. The telencephalic areas are lettered. The course of the nervus terminalis in Scyllium is shown in black. In light outlines the dorsal course of the nerve as seen in Hexanchus, Squalus and others. In Scyllium, instead of a slender external neuroporic canal there is a narrow fissure open both dorsally and ventrally. The somatic area is on the lateral surface . Its outline is projected upon the sagittal plane.
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The anterior commissure lies in the lamina terminalis and connects the striatal areas. The commissure differs greatly in size in different species of petromyzontes and its constitution is not well understood.
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The hippocampal primordia occupying the dorsal part of the walls of the unpaired ventricle converge forward and meet in a sUght thickening of the lamina supraneuroporica (figs. 3 and 4). In this thickening are two kinds of fibers: (1) fibers crossing from the formatio bulbaris of one side to the primordium hippocampi of the other side, and (2) fibers which connect directly the evaginated portion of the so-called striatum. The important thing to notice here is that a decuseation and a true commissure are found here in the pallial position^ that is, above the neuroporic recess.
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SELACHIANS
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In selachians the evagination of lateral lobes has gone farther than in cyclostomes. Especially, the lateral ventricles are longer, the olfactory bulbs are carried out away from the secondary centers. The primordium hippocampi extends out some distance as the roof of the lateral ventricle, invades the lamina supraneuroporica as a great gray mass in which the pallial commissures lie and extends along the upper border of the wall of the unpaired ventricle (figs. 5, 6 and 7). The wall of the telencephalon medium is largely made up of a somatic correlation area, the beginning of the ger eral cortex. That this area is WTongly assigned to the diencephalon by Edinger and others is indicated by the attachment of the velum just in front of the ganglion habenulse (figs. 5 and 6).
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The primordium hippocampi occupies the massive roof and is separated from the medial olfactory nuclei by the external neuropcric recess and a cell-free zone, the zona limitans (fig. 7). It receives from in front fibers of the olfactory tract (secondary) and direct and crossed fibers from both medial and lateral olfactory nuclei (tertiary fibers). The crossed fibers decussate in the lamina supraneuroporica where it is greatly thickened by the primordium hippocampi itself. Also, a large tractus pallii comes up from the hypothalamus to the primordium hippocampi as in cyclostomes. A part of this tract is uncrossed, a part crosses in the
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152
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J. B. JOHNSTON
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foriri bulb
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Fig. 7. Scyllium stellare, schematic transverse section of the telencephalon through approximately the line a-a of Fig. 6. The lateral ventricle is reconstructed from a number of sections before and behind this line.
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postoptic decussations. The primordia of the two sides are connected by true commissural fibers in the anterior paliial commissure (fig. 8). Finally, that portion of the primordium which extends along the telencephalon medium is traversed by great numbers of fine fibers which cross in the superior commissure and constitute a true posterior paliial conrmiissure of the hippocampal primordia (fig. 8).
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From the primordium hippocampi fibers collect forward and descend through the medio-rostral and ventral wall between the lateral ventricles and go to the hypothalamus. They form definite bundles which are undoubtedly homologous with the fornix (fig. 8).
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The existence of a somatic correlation center in the telencephalon is indicated by the presence of large numbers of fibers in the basal bundle which connect this area with the centers of the lemniscus and of the optic tracts in the thalamus. A descending path extending from this somatic area to the ventral part of the thalamus and to the motor centers forms part of the basal bundle described many years ago by Edinger. From the somatic area
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THE EVOLUTION OF THE CEREBRAL CORTEX
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153
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tr.pall
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Fia. 8. Scheme of fiber tracts connected with the primordium hippocampi in selachians, based on Scyllium.
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arises a large part of the fibers going to the nucleus habenulae. These fibers may be given the name tractus tcenioe and are to be sharply distinguished from the fibers arising from olfactory centers, which should be called tractus olfacto-hahenularis. Special tracts serving for correlation between somatic and olfactory centers will be described in a later paper. The somatic areas of the two sides are connected by a true commissure which crosses in the lamina supra-neuroporica above (ectal to) the commissura hippocampi (figs. 7 and 9). This commissure has the essential morphological and functional relations of a corpus caUosum.
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Fi(i. 9. Scheme of fiber tracts of the primordial somatic cortex in selachians, based on Scyllium. The ascending and descending fibers between thalamus and somatic cortical area occupy the middle of the figure and are not lettered.
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154
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J. B. JOHNSTON
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The nervus terminalis enters the forebrain in selachians at a point immediately below and lateral to the neuroporic recess, and its fibers are directed toward the somatic area. This is the true or internal origin of the nerve as far as now understood. In some forms the nerve reaches this point by entering the dorsal surface and running down in the walls of the external neiu-oporic recess. In other forms it enters below and runs up to the same point. This difference is due to the secondary fusion of the medial olfactory regions which, apparently, has in some cases proceeded from below upward and pushed the nerve to the upper surface, in other cases proceeded from above downward and pushed the nerve to the lower surface (fig. 6).
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Fig. 10. Amia calva, schematic transverse section through the anterior commissure. The crossed olfacto-cortical tracts are shown above, the true commissural fibers of the primordium hippocampi below. The letters f.i. mark the sulcus (Monroi) which indicates the line of evagination and the position of the foramen in typical evaginated brains.
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GANOIDS AND TELEOSTS
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In these forms the evagination of lateral lobes has proceeded only so far as to form the olfactory bulbs which enclose lateral ventricles. All the rest of the forebrain constitutes a telencephalon medium whose walls are more or less everted as has been well described by Mrs. Gage and by several later writers (fig. 10) . In the ventricular surface of each wall can usually be seen a sulcus Monroi which leads forward to the lateral ventricle (figs. 2, 10 and 11).
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THE EVOLUTION OF THE CEREBRAL CORTEX
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155
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This sulcus marks the line of evagination and the position of the foramen interventriculare in those forms whose forebrains are evaginated.
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Above this sulcus the ventricular surface of the lateral wall is covered to a variable depth by the pecuUar tissue which constitutes the primordium hippocan pi. Laterally this body is separated from the somatic correlation area hy a sulcus somewhat below the line of the taenia (fig. 10).
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Fig. 11. Sketches for comparison of everted and evaginated types of forebrain. A, transverse section of forebrain of young Amia (25 mm.?); B, diagram to show the translocation of parts that would take place in the evagination of such a brain. The course of the commissure is indicated by continuous lines. In B, the broken lines show the actual course of the "commissura hippocampi" behind the lateral ventricle in amphibians.
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From in front the primordium hippocampi receives olfactory fibers of the second and third orders, many of which decussate in the anterior commissure complex. From behind, the large tractus pallii comes up from the hypothalamus, partly decussating in the anterior commissure (fig. 12). The hippocampal primordium although very different in form, has essentially the same relations as in cyclostomes and selachians.
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The somatic area receives fibers from the lemniscus center in the thalamus, and probably from the tectum mesencephali (fig.
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156
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J. B. JOHNSTON
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12) . Fibers ascending from the lateral geniculate bodies have not yet been seen. In these forms also there is a clear distinction between the tractus taeniae and the tractus olfacto-habenularis. Ganoids and teleosts possess no true anterior pallial commissure. The fibers connecting both the hippocampal and the somatic cortical primordia pass by way of the anterior commissure complex. A detailed discussion of this fact and its connection must be
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Fig. 12. sturgeon.
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Scheme of fiber tracts connected with the primordial cortex of the
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postponed, but it should be held in mind that the commissures of the cortical areas cross beneath the unpaired ventricle, then pass lateral, external and caudal to the foramina and lateral ventricles and so into the everted areas which correspond more or less completely^ to the roof of brains of the evagihated tvpe (figs. 10 and 11).
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THE EVULOTION OF THE CEREBRAL CORTEX 157
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AMPHIBIANS
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The evagination of the lateral lobes has gone much farther and is almost complete. The elongation of the forebrain has taken place not at the olfactory peduncle as in many selachians and teleosts, nor at the telencephalon medium as in some selachians and especially in Chimaera, but in the region between the foramen interventriculare and the olfactory peduncle. The primordium hippocampi has been nearly all evaginated and forms the upper part of the medial wall of the vesicular lateral lobe, together with an undetermined part of the dorsal wall. In urodeles a small part of it remains in the dorsal part of the wall of the un
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FiG. 13. Necturus maculatus, transverse section through the foramen interventriculare. The section is seen from the caudal surface and the commissure related to the hippocampus is represented as passing up lateral to the foramen interventriculare and caudal to the lateral ventricle to reach the hippocampus.
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paired ventricle as in cyclostomes. A zona limitans separates the hippocampal area from the medial olfactory area, which occupies the lower part of the medial wall (*' septum ^^) and extends into the floor of the unpaired ventricle where it forms the '* precommissural body ^' of Elliot Smith (fig. 14).
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The evagination has involved a greater or less part of the somatic area and has been prolonged backward to form a posterior pole. The relations of the hippocampal and somatic areas in this pole are still in doubt.
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158
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J. B. JOHNSTON
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A partial study of the fiber tracts in several amphibians has shown in connection with the primordium hippocampi fibers from the olfactory centers, an ascending tractus pallii from the hypothalamus and a fornix descending to the hypothalamus as in selachians. The lateral forebrain bundle contains many ascending somatic sensory fibers which end in the lateral parts of the hemisphere. According to Herrick there are present in the frog fibers from the lenmiscus centers in the thalamus, optic radiations and auditory radiations. The amphibian brain seems to the writer to present a high degree of complexity and specialization of
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Fig. 14. Necturus, sketch of right half of forebrain seen from the medial surface. The medial olfactory nucleus, precommmissural body and bed of the commissures are shaded by short oblique lines. A part of the preconmiisural body extends up over the foramen interventriculare. The commissure of the primordium hippocampi runs up behind the foramen interventriculare (compare fig. 15).
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irtructure based upon an apparently simple and primitive arrangement of the neurone-bodies in a central gray. More detailed studies of the fiber connections are necessary to enable us to determine the extent and boundaries of the several functional areas, especially the hippocampal and somatic cortical areas and the pyriform lobe.
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The forebrain commissures of amphibians closely resemble those of ganoids and teleosts. In the lamina terminalis are found an anterior commissure chiefly related to the lateral basal bundle and the somatic correlation areas, and a so-called hippocampal commissure (fig. 13). The latter crosses beneath the unpaired ven
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THE EVOLUTION OF THE CEREBRAL CORTEX 159
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tricle, rises lateral and caudal to the interventricular foramen and bends forward over the proximal part of the lateral ventricle to enter the medio-dorsal or hippocampal area. The disposition of this commissure stands in sharp contrast with that of selachians and of reptiles and manmials and agrees in all essentials with that of ganoids and teleosts. When Osborn ('88) interpreted this commissure as the corpus callosum he recognized the great difficulty presented by its position. The writer has pointed out ('02, '06) that this commissure can not be compared morphologically with the psalterium of mammals. The neglect of this by all recent students of the amphibian brain, and especially the failure to observe the difference in position of the conamissures in amphibians and reptiles must lead to confused ideas of forebrain morphology. Compare figs. 14 and 15.
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From the posterior pole of the hemisphere a large posterior pallial commissure accompanies the tractus taeniae to cross in the superior commissure as in selachians.
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REPTILES AND MAMMALS
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From the work of Elliot Smith, His, Ziehen, Zuckerkandl and others the general relations in the reptilian and mammalian brain are well understood. The hippocampal area occupies the mediodorsal region of the hemisphere in reptiles and in the series of mammals is modified, owing to the growth of the general cortex and corpus callosum, until in man the only well developed hippocampal formation Ues between the splenium of the corpus callosum and the tip of the temporal lobe (uncus). From the somatic area of fishes and amphibians the general cortex has developed between the hippocampus dorso-medially and the pyriform lobe laterally. A part of the somatic area surrounding the lateral basal bundle has differentiated into the corpus striatum through which the enlarged lateral basal bundle runs as the internal capsule.
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The disposition of the commissures is of great importance for an understanding of the comparative morphology of the telencephalon. The anterior commissure serves to connect the olfactory
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THK ANATOMICAL RECORD VOL. 4 NO. 4.
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160 J. B. JOHNSTON
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areas and probably contains somatic elements in addition. In mammals two pallial commissures are present, the conmiissura hippocampi and the corpus callosum; in reptiles the corpus callosum is not yet certainly known. A posterior pallial commissure is present in some reptiles but is unknown in mammals.
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In reptiles the hippocampal conmiissure crosses rostral to the unpaired ventricle. Its arms rise up in front of the interventricular foramina in the medial walls of the lateral ventricles, to enter the hippocampal area directly (fig. 15). In lower mammals the hippocampal commissure has the same position as in reptiles and in higher mammals is carried up over the third ventricle by the upward and backward growth of the hemispheres.
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Fig. 15. Sketch of the right half of the forebrain of a reptile to show the relations of the hippocampus and of its commissure. The conunissure goes up in the medial wall in front of the foramen interventriculare.
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An interesting question arises concerning the position of this commissure with reference to the neuroporic recess. This question does not involve the main facts regarding the history of the hippocampus and its commissure in mammals as set forth by Elliot Smith and others, nor does it affect the question at issue between Smith and His as to the primary or secondary character of the fusion which constitutes the commissure bed." The question is whether the commissure lies in the lamina terminalis {below the neuroporic recess) or in the lamina supraneuroporica (above the
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THE EVOLUTION OF THE CEREBRAL CORTEX
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161
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neuroporic recess). In reptiles the hippoeampal commissure lies more or less close to the anterior commissure so that in late embryos and adults the relations of the neuroporic recess are obscured. In lizards it is probably represented by the recessus inferior of Elliot Smith (fig. 16). The early development shows that the neuroporic recess is situated close in front of the anterior commissure, that above the recess is a thickened part of the lamina supraneuroporica related to the hemispheres; the remainder of this lamina is a membranous tela in which appears the paraphysis just in front of the velum transversum (fig. 17). As the hemispheres
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Fig. 16. A portion of a transverse section through the brain of a monitor (Hydrosaurus). From G. Elliot Smith. In the figure to the left the line x-y shows the plane of the section, ah., alveus; c./., columnafornicis ;/asc., fasciculus marginalis; /tip., hippocampus; yara., paraterminal body; rzc. i., recessus inferior; rec, «., recessus superior ;c. d., hippoeampal commissure;c. v., anterior commissure.
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develop the recessus neuroporicus is reduced or obliterated and the hippoeampal commissure comes to lie close to the anterior commissure.
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In mammals the neuroporic recess is a prominent pit in front of the anterior commissure in early stages, but the growth of the hemispheres and commissure-bed reduces it to a shallow pit in the same position (figs. 18 and 19). The thickened lamina which constitutes or contains the bed of the hippoeampal commissure is the lamina supraneuroporica and extends laterally into the hemispheres as in reptiles. When the hippoeampal commissure ap
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162 J. B. JOHNSTON
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pears it is widely enough separated from the anterior eonunissure so that there can be no doubt that it lies above the neuroporic recess in the lamina supraneuroporica (figs. 18 and 19).
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In reptiles and manmials the commissura hippocampi and corpus callosum are said to be embedded in the preconmiissural body (Elliot Smith and others). This preconmiissural body is formed by the invasion of the lamina terminalis by the medial olfactory nuclei or by the secondary fusion of these nuclei. Such a fusion is most extensive in selachians where the nuclei are very vol imi
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FiG. 17. Median sagittal section of the brain of a turtle embryo at the time of formation of the paraphysis. The broken line marks the di-telencephalic boundary. At m is the caudal margin of the nervous part of the lamina supraneuroporica. The tela behind this is not only thin but differs histologically from the lamina supraneuroporica. The neuroporic recess has been traced in earlier stages and undoubtedly lies between the parts identified in this figure as the anterior commissure and the lamina supraneuroporica.
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nous. In some mammals also this fused body is very large. So far as my observations go the corpus callosum in mammals is situated along the line of the zona limitans, while the hippocampal commissure is involved or enwrapped to a variable extent in the precommissural body. I can harmonize this with the condition in selachians and -with the facts of development in mammals above cited only on the supposition that the precommissural body has secondarily pushed up into the region of the lamina supraneuroporica, probably following along the system of olfacto-hippocampal fibers.
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THE EVOLUTION OF THE CEREBRAL CORTEX 163
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The bearing of these facts upon the phylogeny of the cortex and its commissures is seen when the brain of the mammalian embryo is compared with the selachian brain (fig. 20). The paUial areas in selachians, reptiles and mammals meet in the lamina supraneuroporica which is thickened by invading gray matter and serves for the passage of the hippocampal commissure and corpus callosum. The cy clostomes present the same condition, but with simpler commissures. The ganoids, teleosts and amphibians present a very
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Fio. 18. Median sagittal sections of the forebrain in cat embryos to show the relations of the commissures to the recessus neuroporicus. To the left a 12 mm. embryo (Minot collection No. 400, slide F., sec. 3/6) ; to the right, a 31 nmi. embryo (Minot collection No. 527, slide Bk, sec. l/3). The section of the 12 mm. stage is slightly oblique. The paraphysis is drawn in dotted outline as it appears in adjacent sections. The slight thickening at ^ «., shows that the lamina supraneuroporica is passing over into the medial wall of the hemisphere. The point m corresponds to the point so lettered in the turtle embryo. This is about the point at which the recesses neuroporicus has been placed by previous authors. The nearness of this to the paraphysis is sufficient evidence that the lamina terminalis does not extend up to this point. The figures are from free-hand sketches but the relations are essentially correct.
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different condition, in which the fibers analogous to the hippocampal commissure and corpus callosum, so far as such fibers exist, run with the anterior commissure in the lamina terminalis. It seems probable that the pallial commissures maintain a true pallial position in cyclostomes, selachians, reptiles, birds and mammals (and possibly dipnoans), while in ganoids, teleosts and
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164 J. B. JOHNSTON
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amphibians they have a peculiar disposition the origin of which requires to be explained.
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The features in the author's account of the evolution of the cerebral cortex which are distinctive are the following:
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1. The telencephalon possesses an unpaired ventricle whose walls constitute a very important part of the forebrain (telencephalon medium).
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2. The telencephalon of primitive vertebrates possesses visceral and somatic correlating centers which are the primordiaof the^^hippocampal formation and general cortex respectively.
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•oraph.
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Fig. 19. Sagittal sections of the forebrain in rabbit embryos to show the relations of the commissures. To the left an embryo of 14 days, 10.5 mm. (Minot collection No. 156); to the right an embryo of 20 days, 29 mm. (Minot collection no. 171.) Drawn as fig. 18.
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These correlating centers are equally old (unless the somatic be the older) and the terms archipallium and neopallium are inappropriate. In their stead should be used some such terms as visceral pallium and somatic palUum.
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3. These cortical primordia are at first not involved in the evagination of lateral lobes, but lie in the wall of the unpaired ventricle. They are gradually evaginated into the lateral lobes in selachians, dipnoans, amphibians and reptiles.
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4. The primordium of the visceral cortex is defined by (1) the entrance of olfactory fibers of the second and third orders, (2) the
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THE EVOLUTION OF THE CEREBRAL CORTEX
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165
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entrance of an ascending tract from the hypothalamus of general visceral or gustatory function or both, (3) the possession of a troie commissure in the lamina supraneuroporica and another in the superior conmiissure (anterior and posterior pallial conunissures), (4) the presence of true fornix, and by (5) pecuUar histological structure. With regard to the conamissures, the cyclostomes require further investigation, the ganoids, teleosts and amphibians present a peculiar modification of the anterior pallial commissure and the mammals apparently lack a posterior pallial conamissure.
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Fig. 20. Sketches for comparison of the human embryonic forebrain with that ol the selachian. On the left a sagittal section of the forebrain of Squalus acanthias of about 70 mm., from a preparation in the Minot collection. On the right a median sagittal section of the forebrain of a human embryo (Minot collection no. 181, slide Al. s«c. l/3). Drawn as fig. 18.
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5. The primordium of the somatic cortex is defined by (1) the entrance of ascending fibers from the thalamus (and tectum mesencephali) chiefly carrying cutaneous, visual and muscle-sense impulses (exteroceptive and proprioceptive centers) , (2) giving origin to descending fibers to the thalamus and probably medulla oblongata and spinal cord (Van Gehuchten and others), and (3) the possession of a true pallial commissure (corpus callosum) in the lamina supraneuroporica except ganoids, teleosts, and amphibians. The writer does not accept Edinger's hypothesis that the oral sense
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166 J. B. JOHNSTON
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centers in the telencephalon play the chief role in the origin of the cerebral cortex. The area recognized by the writer as the primordium of the somatic cortex has been assigned by all recent authors to the diencephalon and is wholly distinct from any center which Edinger has suggested for his oral sense. A cutaneous nerve of the first head segment (nervus terminalis) probably entered the primordium of the general cortex, but this is not an essential part of the account here given.
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I wish to express my best thanks to Dr. C. S. Minot for the opportunity to study his valuable collection of mammalian embryos.
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Accepted by the Wlstar Institute of Anatomy and Biology April 2. Printed May 20. 1910.
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ON THE GENESIS OF AIR CELLS IN THE CONCH^K
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NASALES^
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JACOB PARSONS SCHAEFFER
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Cornell University Medical College^ Ithaca, N. Y. WITH SEVEN FIGURES.
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Since the time of Santorini, who apparently was the first anatomist to call attention to the cavities frequently found in the middle nasal conchae, many conflicting and erroneous hypotheses have been advanced as to the nature and origin of these spaces. Many of the theories are from the pens of clinicians who removed at operation portions of the walls of such cavities that were changed by pathological processes, and then attempted to explain the origin of these spaces from the altered tissue removed.
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It is the purpose of this paper to briefly analyze some of the theories extant and, if possible, arrive at the true origin and nature of these cavities — basing the conclusions on a study of the lateral wall of the nasal cavity in the fetus, child, and adult.
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These cavities have been variously termed cysts, abscesses, osseous cysts, exostoses, neoplasms, ectasias of the ethmoid bone, air cells, aberrated ethmoid cells, and when large and occyrring in the ventral portion of the conchae mediae, as conchae bullosae.
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I have found these cavities, which I consider as normal ethmoid cells, in the concha media, processus uncinatus, and agger nasi. Schaeffer reports an isolated case in the concha inferior, and Bayer found one in the concha superior. The usual seat, however, for these cells is in the anterior half of the concha media, and it is to the cells in this position that the above terms have been applied by various writers. It is not common to find cells in the adult superior conchae. The reason for this is evident
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^Presented at the 25th session of the Amer. Assoc. Anat., Boston, December, 1909.
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168 JACOB PARSONS SCHAEFFER
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when we remember that the adult superior ethmoidal concha' are as a rule merely thin lamellae of bone coverirg medially the posterior group of ethmoid cells. The most prominent concha? in this position are due to large posterior ethmoid cells which push the median walls of the cells toward the cavum nasi; thus forming more pronounced swellings, therefore seemingly larger superior ethmoidal conchae. It must, however, be remembered that the ethmoidal conchae are primarily solid appendages of the lateral ethmoidal masses. The developing posterior group of ethmoid cells do not only extend into the lateral ethmoidal masses, but also into the superior ethmoidal conchae. This extension progresses until the conchae are represented finally by mere thin lamellae of bone, covered and lined with mucous membrane. In this sense, portions of posterior ethmoid cells are always conchal cells, just as are those which occupy the middle conchae.
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Conchal cells are practically unknown in the concha inferior, because the latter structure is too far removed from the seat of the modifications in the ethmoidal region consequent upon the formation of the ethmoidal fissures, the structures overhung by the concha media, and the Anlagen of the paranasal chambers.
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Santorini (1739) in his Observationes Anatomicae (p. 89), calls attention to cavities in the ventral end of the ccncha media and claims priority in describing them. He found the cavities both in cadavers and skeletons, but was unable to find ostia Tor these spaces. He suggests that his failure infindir.g openings for the cavities might be due either to the softness of the mucous membrane or smallness of the apertures, and concludes that his successors may find ostia for these spaces. He says: Ejustamen inveniendi alterius erit otii, et sedulitatis opus."
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Depuytren ('30) speaks of them clinically under the title of ^^Kyste k parois osseux pris pour un polyp fibro-celleux, and Chantreuil ('69) examined and described a specimen under the title of Exostose Olluleuse des Fosses Nasales.
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Glasmacher ('84) writes on ^'Knochenblasenbildung in der Nase, and describes a cell 22 mm. long and 18 mm. wide. He says:
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ON THE GENESIS OF AIR CELLS IN THE CONCHiE N AS ALES 169
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Was nun die Knochenblasenbildung im Bereiche der Muscheln angeht , so beraerke ich vorab, dass ich diese ebenso wenig, wie im Siebbein fiir pathologisch ansehe; ihre Wichtigkeit liegt nur in ihrem abnormen Wachsthum.
 +
 +
Schaefifer ('86) speaks of these cells and reports four eases one of which he found in the ventral end of the concha inferior — the only cell of this concha I have been able to find reported in the literature. I will again refer to this cell in a subsequent paragraph, in an attempt to explain its genesis. He considers the cavities of pathological origin, and in defence of his belief he offers the following:
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Zudem gaben die Patienten an, dass sie seit Jahren nach Erkaltungen eine Zunahme der Stenose des Nasenganges beobachtet batten. Dieses Wachsen setzt doch gewisse Reize voraus, die es veranlassen, wenn anders die ganze Knochenblase nicht angeboren ist, was in meincn Fallen nicht der Fall war. Solche Processe miissen wir aber immer unter die pathologischen einrechnen.
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He apparently fails to recognize that a normal ethmoidal cell developing in the concha media will gradually lessen the lumen of the nasal fossa. A conchal cell will always begin small, and develop just as the ethmoid cells of the lateral mass but in many cases remains of such size as to cause no trouble, and only when excessively large or diseased is the attention of the clinician directed to it — unless discovered accidentally when exploring this region of the nose for some other cause. The stimulus or irritant of which Schaefifer speaks causing the growth of these cavities is certainly not diflferent from the stimuli which cause the formation of the other paranasal sinuses.
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Macdonald ('91) writes on these cells under the title of, '*0n Cyst and Abscess of the Middle Turbinated Bone. In a previous discussion he attempted to show that the development of such structures might be analogous to similar tumors of long bones, " and in the article under the above titlie he concludes the theory as hasty and incorrect" — then advances his osteophytic theory. Since the latter theory has found its way into many
 +
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170 JACOB PARSONS SCHAEFFER
 +
 +
articles, also into some text-books, it may not be amiss to quote briefly from his original paper.
 +
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The process in all probability begins in an osteophytic periostitis, a condition common in this region, and resulting in a general increase in the size of the bone in every diameter. The free margin being incurved upon itself, from the pathological process just mentioned, will bring it in contact and ultimately in union with the body of the bone. Thus a cavity may become enclosed and sealed at all points by a similar process occurring at the extremities/ He further says: "That the above is the correct explanation of the lemarkable neoplasms is proved by a microscopical examination of any portion of the cyst wall; on each side of the thin lamina of bone is found a layer of mucous membrane covered with columnar epithelium."
 +
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The theory as advanced by Macdonald seems fanciful and to my mind is certainly not the true explanation of the origin of these cavities. In some cases there is a slight lateral and superior curling of the free border of the concha media, thus increasing the extent of the so-called sinus of the concha media, but this sinus is in no way the homologue of conchal cells. Testut and Jacob also refer to this curling of the concha media with reference to cell formation.
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According to my specimens, cells invariably have ostia conamunicating either with the anterior or posterior ethmoid cells, with the inferior ethmoidal fissure (meatus superior) or the infundibulum ethmoidale. Some cells conamunicate directly with the meatus medius under cover of the concha media. Lothrop's investigation of these cells fully confirms this. He says:
 +
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'Every cell without exception possesses an ostium. ' ' In the second
 +
place, Macdonald's theory could not account for the cells having their ostia opening into the meatus superior, nor for those conrnaunicating with the infundibulum ethmoidale — y^t in my cases fully one-half of the cells open in these positions. The only factor in defense of the theory is that the cavities are lined with colunmar epithelium. However, this may be explained in a far more satisfactory manner if we consider the development of these cells as analogous to that of the ethmoid cells of the lateral masses. In fact very many of these cells are merely parts of other ethmoid cells (figs. 4 and 5).
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ON THE GENESIS OF AIR CELLS IN THE CONCHiE NASALES 171
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Knight ('92) reported a case under the title of, *'Cyst of the Middle Turbinate/' He mentions two possible theories, viz : (a) the result of a rarefying osteitis,*' (6) that of Macdonald as given above. In his text-book ('03) he says :
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In the majority of cases it doubtless results from a rarefying osteitis inducing absorption of the interior of the body of the bone.
 +
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This latter theory is not permissible when we recall that these cells or cavities are lined with mucous membrane similar to that of the ethmoid cells of the lateral masses.
 +
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Reardon C98), writes on Osseous Cysts of the Middle Turbinate." He thinks the cavities are either ectasias of the ethmoid which, as the ethmoid develops, become separated from it completely or incompletely; or are aberrated ethmoidal cells which developed in the conchse (He5rmann's theorj') It is easily understood why many clinicians continually refer to these cavities as cysts, osseous cysts, abscesses, etc., Decause they generally have their attention directed to them only when they are diseased, unless the air cell becomes very large without disease and leads to symptoms of obstruction and pressure. They then attempt to explain the genesis of these primarily normal cells from the pathological condition found.
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It must be remembered that these conchal cells, like any of the ethmoid cells or other paranasal sinuses, may become the seat of an empyema or mucocele, and enlarge, because the ostia of these cells are invariably placed at the highest points of the cavities and very disadvantageously placed as drainage openings — a fact easily understood if we consider their development. The existence of air cells in the conchse, etc., is certainly not the result of an empyema or rarefying osteitis, but because these cells are normally found in these positions, they may become the seat of pathological conditions just as any other cell of the ethmoid labyrinth.
 +
 +
Zuckerkandl refers to the distension, by an air cell, of the ventral extremity of the concha media as, "concha bullosa."
 +
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Lothrop after studying a large number of these cavities in adult specimens concludes that they are ethmoid cells — a view also held by Shambaugh, who speaks of them as anatomical variations of ethmoid cells."
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In order to better understand these cells and see that they are nothing other than ethmoid cells, it is essential that we briefly consider the origin of the ethmoid labyrinth. The location of these cells appears less abnormal when we recall that the ethmoidal conchsB and uncinate processes are merely appendages of the lateral ethmoidal masses. There is no reason, therefore, why ethmoid cells should not at times, in the formation of the ethmoid labyrinth, grow into these appendages just as they grow into the lateral ethmoidal masses.
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According to my reconstructions of the lateral wall of the nasal cavity of different aged fetuses, the primitive ethmo-turbinal fold, with its subsequent modifications is not only concerned in producing the ethmoidal conchse and intervening furrows (meati), but also the structures operculated by the middle nasal soncha: viz., the processus uncinatus, the bulla ethmoidalis, the hiatus semilunaris, and the infundibulum ethmoidale. These modifications are also intimately related with the Anlagen of the paranasal sinuses.
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The posterior group of ethmoid cells are primarily constricted from, or are direct extensions of, the furrows separating the primitive ethmoidal conchse, and the anterior group develop from the preformed accessory fiurows of the middle meatus — whence are in relation with the grooving and structures found in this location.
 +
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Frontal sections of the fetal nose before birth (fig. 1) already indicate the Anlage of the ethmoid labjn'inth, and at term it is comparatively well advanced (fig. 2). In this connection it is an interesting fact that the ostia of conchal cells invariably conrniunicate directly or indirectly with the points at which the ethmoid cells developed their Anlagen. These cells are either parts of other ethmoid cells (figs. 4, 5), or they conmiunicate directly with the superior meatus (fig. 4), with the infundibulum ethmoidale (fig. 6), or directly with the ventral end of the middle meatus (fig. 5). The ostia in the latter case are on the lateral wall of the concha media.
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ON THE GENESIS OF AIR CELLS IN THE CONCHiE NASALES 175
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Fig. 4. Drawing from a specimen of the lateral nasal wall. The cell extending into the agger nasi and into the processus uncinatus communicates with the infundibulum ethmoidale. Note that the ethmoid labyrinth is largely replaced by a very large bullous cell extending into the concha media and communicating with the ventral extremity of the meatus superior.
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Fig. 6. Drawing from a specimen of the lateral nasal wall. The arrows indicate the ostia of the several cells. Note that one of the cells which communicates with the meatus superior extends into the concha media. Note also the cell in ventral extremity of the concha media with an independent ostium conmiunicating directly with the meatus medius.
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THB ANATOMICAL BBCOBD VOL. 4 NO. 4.
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176 JACOB PARSONS SCHAEFFER
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Although theAnlagenof the ethmoid cells are prunarily constrictions from the nasal fossse, yet the extension and development of these cells depend upon the simultaneous processes of growth (of the sacs) and resorption (of surrounding tissue). In this manner, as age advances, the cells extend farther and farther into the lateral masses of the ethmoid bone, and in the adult are completed by the articulation of the ethmoid bone with the frontal, lacrimal, sphenoid, maxillary, and palate bones. These developmental processes are doubtless in some cases carried further than in others, hence the extension of ethmoid cells not only farther into the lateral masses of the ethmoid bone, but also into its appendages, such as the ethmoidal conchse and uncinate processes. Ethmoidal cells also at times extend into the agger nasi and encroach upon the sinus frontales and sphenoidales.
 +
 +
A reference to figs. 4 and 5 shows the extension of the inferior ethmoidal groove (meatus superior) not only into the lateral mass but also into the concha media, thus forming conchal cells which are merely parts of the lateral mass cells. At first thought it may seem difficult to account for the conchal cells having their ostia opening inferior to the attachment of the concha media, either into the middle meatus or the infundibulum ethmoidale (figs. 4, 6, 6). However, when we remember the great modifications of this portion of the middle meatus overhung by the concha media, consequent upon the formation of the structures found here, and that the anterior group of ethmoid cells have their origin in this position, it is not difficult to see how some of these cell-Anlagen may extend not only into the lateral mass of the ethmoid bone, but also into the uncinate process, the concha media, and the agger nasi (figs. 4, 5^-6). Fig. 3 shows a small cell already present in the concha media of a fetus at term. Of course most conchal cells must necessarily appear comparatively late in the formation of the ethmoid labyrinth, since the positions they occupy with reference to the ethmoid cell Anlagen are relatively far removed. The extensions into the conchse, etc., would, therefore, in most cases be delayed — probably until puberty, or even later, when the ethmoid labyrinth reaches its full development. This explains Knight^s statement : * * Children seem to be exempt. None of my patients was under 20 years of age.
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ON THE GENESIS OF AIR CELLS IN THE CONCHiE NA8ALES 177
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Fig. 6. Drawing from a specimen of the'lateral nasal Vail. Note the large cell in the concha media communicating with the infunidbulum ethmoidale.
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Fig. 7. Drawing of a frontal section through the head of an adult. Note the bilateral conchal cells in the middle nasal conchse.
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178 JACOB PARSONS SCHAEFFER
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Figs. 4 and 5 show the extension of ethmoid cells into the agger nasi. There is no reason why cells in this location should not extend farther, and finally reach and occupy the ventral end of the concha inferior. Such an extension would explain Schaeffer's cell of the ventral end of the inferior nasal concha.
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Occasionally multiple cells are present, separated by thin partitions — each cell having an independent ostium, or in communication with either a cell of the anterior or one of the posterior group (fig. 5). Both conchae mediae of the same individual may contain cells (fig. 7), or one may be free of such cavities and the other contain one or more cells. Figs. 6 and 7 show the bullous type of cells — termed by Zuckerkandl '^conchae buUosae."
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Sex apparently does not have any bearing on the development of conchal cells, and they are about equally divided as to whether the ostia open superior or inferior to the attached border of the concha media.
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The cells found in the conchse, uncinate processes, agger nasi, and those extending into the frontal and sphenoidal sinuses, do not differ in any manner from the ethmoid cells of the lateral masses. The mucous membrane lining these conchal cells is extremely thin, but corresponds in its general structure with that lining the other ethmoid cells — unless changed by a pathological process.
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Santorini thought the condition quite common, but says he should not venture to say that the condition is constant. He apparently regarded these cells as much more common than they really are. According to Reardon, Zuckerkandl observed them eight times in 172 skulls. Knight says that Zuckerkandl '^ found them thirty-six times in 200 post-mortem examinations.'^ Lothrop found them in 9 per cent of all cases, and 11 per cent of the writer's specimens showed cells in the locations mentioned in a previous paragraph. The latter conclusions are based upon an examination of 150 adult nasal fossae.
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ON THE GENESIS OF AIR CELLS IN THE CONCHiE NASALES 179 CONCLUSIONS
 +
 +
1. The cells found in the concha nasalis media, agger nasi, and processus uncinatus are true ethmoid cells, because:
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(a) They differ in no manner from the cells of the lateral ethmoidal masses;
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(6) Their ostia are invariably located at the points from which the ethmoid cells developed their Anlagen ;
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(c) They are frequently merely portions of lateral mass cells.
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2. The cells invariably have ostia which conmiunicate either with the superior meatus, with the ethmoidal infundibulum, or directly with the middle meatus.
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3. The conchal cells may become the seat of a mucocele, abscess, etc., just as may the cells of the lateral ethmoidal masses, but to say that these cells owe their genesis to such pathological conditions is erroneous.
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4. The so-called middle conchal sinus formed by the lateral and superior curling of the free border of the concha media is not homologous with, nor analogous to a conchal cell; nevertheless in some cases it may retain fluid in its hanunock-like fold. The majority of conchae mediae, however, do not show this sinus, and when present it is, as a rule, of minor importance.
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BIBLIOGRAPHY
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Chantreuil. Bui. Soc. Anal, de Paris, vol. 44, p. 83.
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1869 Depuytren. Clinique Paris, vol. 11, pp. 174-179.
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1830 Glasmacher. Knochenblasenbildung in der Nase. Berliner Klin. Wochen^chr.,
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1884 vol. 21, pp. 571-573.
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Knight, C. H. Cyst of the middle turbinate. The New York Med. Journal,
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1892 vol. 55, p. 309.
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1903 Diseases of the nose and throat, pp. 44-45.
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LoTHROP, H. A. The anatomy of the inferior ethmoidal turbinate bone with
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1903 particular reference to cell formation. Annals of Surgery,
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vol. 38, p. 244. Macdonald, Greville. On cyst and abscess of the middle turbinated bone.
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1891 The Lancet, vol. i, 69th yr., p. 1374.
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Reardon, T. J. Osseous cysts of the middle turbinate. Boston Med. and
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1898 - Surg. Jour., vol. 129, p. 569.
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180 JACOB PARSONS SCHAEFFER
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Santorini, Dominici Joannes. Observationes Anatomicje, pp. 88-89.
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1739 ScHAEFFER, Max. Knochenblasenbildung in der NasenhShle. Chir. Erfah 1885 rungen der Rhinol. and LaryngoL, pp. 11-13.
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Shambauqh, Geo. E. The construction of the ethmoid labyrinth. Trans.
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1907 Amer. LaryngoL Assoc, pp. 110-121.
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Testdt and Jacob. Trait<5 D' Anatomic Topographique. Tome Premier, p. 433.
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1905 '
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ZucKERKANDL, E. Die untcrc Siebbeinmuschel (mittlere Nasenmuschel), Nor 1893 male und pathologische anatomic der Nasenhohle und ihrer
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pneumatischen Anhangc. Bd. i, pp. 62-65
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Aocepted by the Wbtar Institute of Aoatoiuy and Biology March 30. Printed May 20. 1010.
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SUPPLEMENTARY ANNOUNCEMENT
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THE II. INTERNATIONAL CONGRESS OF ANATOMY Brussels f August 7-11, 1910
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The American Association of Anatomists is one of five national anatomical associations participating in the II. International Congress of Anatomy. This congress will constitute the twenty-sixth session of the American Association of Anatomy. Members intending to attend this congress are requested to notify the Secretary of the American Association of Anatomists at an early date and transmit to him titles of papers or demonstrations they desire to present. Titles must be in the hands of the Secretary of the American Association not later than June 25.
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Inquiries concerning Anatomy, Comparative Anatomy and Embryology may be addressed to Professor Brachet, rue Snesscns 18, or Doctor E. Willems, rue Paul Lauters 5.
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Inquiries concering Histology may be addressed to Professor Joris, rue du Prfeident, or Doctor Sand, rue des Minimes.
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Inquiries concerning lodgings and requests to have rooms reserved should be addressed to Doctor Brunin, Chef des travaux, 18 Avenue de la Renaissance.
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The scientific sessions will be held during the forenoons, from 9 to 1 o^clock, in the physical lecture room of the University, 14 rue des Sols; the demonstrations in the Anatomical or Physiological Institutes, Park Leopold.
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G. Carl Huber, Secretary^ 1330 Hill Street, Ann Harbor, Michigan.
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We are also imformed by the Rockefeller Institute that Professor Jacques Loeb has been appointed head of the new department of experimental biology. "Here he will go on with his scientific work, following his own genius without special reference to problems in medicine, to which ultimately everything refers." Loeb is well known to anatomists by his work on regeneration, teratology and experiments of fertilization, and his appointment by the Rockefeller Institute is therefore of signifi
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182 SUPPLEMENTARY ANNOUNCEMENT
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cance to anatomists. That this Institute is so foresighted in its plans is a source of gratification to those who are promoting scientific anatomy. The splendid example that the Rockefeller Institute is setting in medical research may be received as a hint to our medical schools that are striving so hard to move forward. Every great medical school should be a Rockefeller Institute, and it is clear that this is possible only by the appointment of great men as professors.
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We are authorized to announce that Prof. H. D. Senior of Syracuse University has accepted the call to the chair of anatomy at New York Universitjr (Bellevue). With one exception, this appointment completes the reform of the anatomical departments in the twenty-five leading medical schools. In them the example set by the University of Pennsylvania, Harvard, the University of Michigan, Columbia and Johns Hopkins has been followed by filling the chairs of anatomy with professional anatomists, which we believe to be a marked step in advance.
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THE RELATION OF THE MYOTOMES TO THE VENTRaLATERAL MUSCULATURE AND TO THE ANTERIOR LIMBS IN AMBLYSTOMA
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WARREN H. LEWIS
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From the Anatomical Laboratory ^ Johns Hopkins University
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WITH EIGHT FIGURES
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THE NORMAL DEVELOPMENT
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The formation of the myotomes begins at an early stage before the tail bud makes its appearance. At a stage, shown in fig. 1,^ in which there is a small tail bud present, there are fifteen myotomes and the sixteenth is partly formed. At this stage the anterior myotomes have just separated off from the lateral mesoderm. The first myotome is irregular in shape and lies m close relation with the gill mass. The third, fourth and fifth myotomes are still attached to the pronephros. The ventral processes of the first three myotomes are just beginning. Fig. 2, shows a stage, about two days later. There are no signs of the arm bud at this time, either in the dissected specimens or in the cross sections. From now on, there is a rapid growth of the ventral processes of the myotomes. The ventral processes of the anterior three myotomes pass in front of the pronephros, while the fourth lies behind. These ventral processes avoid the region of the pronephros and futiu'e arm bud and gradually grow over the lateral surface of the embryo, the first one faster than the second, the second faster than the third, and so on, so that the first and second may be well advanced before the seventh and eighth appear.
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At a somewhat later stage than that shown in fig. 2, we find that ventral to the pronephros the ventral processes of the third and the fourth myotomes unite to make this lateral sneet continuous.
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^ The figures are all from dissected specimens, which were fixed in corrosiveacetic solution.
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THB ANATOMICAL RSCOBD, VOl. 4, NO. 5.
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184
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WAKREN H. LEWIS
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Fig. 1. Operating stage, my I, first myotome ; pro, pronephros; sp, spinal cord; g, gill mass.
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pro Fig. 2. Somewhat later stage showing ventral processes of anterior myotomes.
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The ventral processes of the first, second, and third become completely separated from the myotomes, partly by the pronephros, and form the stemo-hyoid portion of the ventral musculature. From the first segment of the sterno-hyoid the genio-hyoid arises. The pronephros also gradually separates a portion of the ventral process of the fourth segment from its dorsal part. The segmentation of the ventro-lateral musculatiu'e can be observed even after the musculature is split into different layers. From the first and second myotomes a lateral chordal mass early splits ofif and is separated from the dorsal portion of the myotome by the vagus ganglion and the otic capsule. Fig. 3, shows normal relations of an embryo twenty days older than the one shown in fig. 1. The arm has been dissected away leaving only the myotomic musculatiu'e. The arm bud does not appear until sometime after the operation stage (fig. 1) and lies in close relation to the
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Fio. 3. Normal larva twenty days after operation stage, leg has been dissected away, my I, first myotome; oc, otic vesicle; gehy, genio-hyoid; sthy, stylohyoid; Ic, lateral chordal muscle; pro, pronephros.
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pronephros in the region of the second, third, fourth and fifth myotomes, mainly the third and fourth.
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The cells of the arm bud apparently arise from the somatopleure in the region of the pronephros and not from the myotomes, they gradually form a protuberance on the surface of the embryo. The lateral myotomic muscle sheet gradually spreads out beneath the arm mass, that is medial to it but superficial to the pronephros.
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EXPERIMENTS
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In the following series of experiments with the exception of the second, I have attempted to remove various myotomes at the stage shown in fig. 1, that is, at the time just after the myotomes have separated off from the lateral mesoderm. The following results are based not only upon the study of dissected specimens but upon serial sections as well.
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In the first series attempts to remove the first myotome only were not entirely successful, although in a number of experiments it was found that twenty days after the operation the dorsal part of the first myotome was almost completely absent and in such cases the anterior segment of the lateral chordal mass was very small. In all of these experiments however, the anterior end of the ventral muscle mass, namely the sterno-hyoid was present, though smaller than normal in one case. The failure to extirpate completely the first myotome was probably on account of the diffi
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186 WARREN H. LEWIS
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culty of cutting out the ventral portion, which lies in such close relation with the gill mass, and which gives rise to the anterior end of the ventral musculature.
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In the second series of experiments, an attempt was made to remove the ventral halves of the first three myotomes at a stage slightly older than that shown in fig. 1. In one partially successful experiment killed twenty days after the operation the dorsal part of these three myotomes was intact. The lateral chordal part of the first myotome was entirely wanting and that of the second myotome very much smaller than normal; the first segment of the ventral muscle mass, that is of the sterno-hyoid, was entirely wanting, and also the genio-hyoid which arises from it. The second ventral segment was very small and thin, while
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Fio. 4. Larva twenty days after removal of anterior three myotomes (first and third only partly removed). The lateral chordal and ventral derivatives of these myotomes are wanting.
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the third was apparently normal. In the remaining experiments of this series the dorsal and lateral chordal portions of the myotomes are apparently uninjured while the sterno-hyoid and geniohyoid muscles are smaller than normal especially at the anterior end where they are almost completely wanting in some of the experiments. It is evidently difficult to remove the ventral portion of the myotome entirely at this stage.
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In the third series of experiments an attempt was made to take out completely the first three myotomes with the ectoderm over them. In an embryo killed twenty days after the operation, the conditions were found as shown in figure 4. The dorsal part of the first myotome is small, the first segment of lateral chordal mass and the sterno-hyoid are wanting as well as the genio-hyoid.
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EXPERIMENTS ON MYOTOIKS OP AMBLYSTOMA
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187
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The second myotome as well as its derivatives is entirely absent. The third myotome is small and the third segment of the sternohyoid is absent. It is very evident that one need not extirpate the entire myotome in order to prevent the development of the ventro-laterai derivatives. In another experiment, the embryo was killed ten days after the operation, the dorsal part of the first myotome was found to be very small, while that of the second and third were wanting. The lateral chordal as well as the ventrolateral musculature derived from these segments was found to be absent as in fig. 4. The fourth ventral segment was, however much more elongated than the one shown in fig. 4. The other experiments of this series show various degrees of extirpation of these myotomes, usually with the corresponding absence of their derivatives, namely the lateral chordal mass and the stemo-hyoid
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y.J^Q» 6. Larva nineteen days after removal of the fourth myotome. Dorsal view.
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188
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WARREN H. LEWIS
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Fig. 6. Lateral view of larva shown in fig. 5. The ventral muscular derivative of the fourth myotome wanting.
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and genio-hyoid muscles, or in some cases where these derivative muscles are not entirely wanting, they are found to be smaller than normal.
 +
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In the fourth series of experiments, I attempted to take out the fourth myotome only. In one very successful experiment, apparently this entire myotome was extirpated; as a result, we find nineteen days after the operation that the myotome and its muscle derivatives are entirely wanting, see fig. 5 and 6. In another experiment where the myotome was apparently entirely extirpated we find that the ventro-lateral muscle forms a continuous sheet. This is due to the elongation of the preceding and succeeding segments of the ventro-lateral musculature to fill in the gap.
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In the fifth series of experiments, I attempted to remove the second, third, fourth and fifth myotomes. These myotomes were apparently completely extirpated in an embryo killed twentysix days after the operation. Figs. 7 and 8 from a dissection show the following results. The second, third, fourth and fifth myotomes are completely wanting, as are also the muscular derivatives of these myotomes. We find that the sixth myotome (both dorsal and ventral portions) has elongated, the dorsal portion to nearly the length of three myotomes, and the ventral portion so as to partly fill in the gap between it (figs. 7 and 8) and the first segment of sterno-hyoid muscle. In fact, the ventral edge of the ventral muscle has extended so as to meet the elongated first segment. In another experiment, the third and fourth myotomes were apparently completely extirpated and the second and fifth
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EXPEBIMENTS ON MYOTOMES OF AMBLY8TOMA
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189
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my VI
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Figs. 7 and 8. Larva killed twenty-six days after complete removal of the second , third, fourth and fifth myotomes. Dorsal and lateral views. The muscular derivatives of these myotomes wanting.
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partially. The ventral lateral muscle shows complete absence of the third and fourth segments and imperfect development of the second and fifth, while the sixth segment is very much elongated. The gap, however, which might be expected from the complete absence of the third and fourth segments is nearly filled in by the elongation of the ventral portions of the remaining segments. Still other experiments show much the same results, the condition of the ventral musculature depending upon the degree of extirpation. This elongation of segments to fill in the gap caused by the extirpation of certain segments takes place in nearly all of the experiments and probably would be complete if the animals were allowed to live for a greater length of time after the experiment. The condition found by Miss Byrnes^ in her experiments on Amblystoma in which, after destruction of the ventral halves of the myotomes in the region of the posterior limb the ventral musculature was present, is evidently to be explained through elongation of the remaining myotomes or their ventral processes. It is very unlikely that this regeneration takes place from the muscle of the opposite side as there is a wide gap between the two sides in the mid- ventral line.
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190 WARREN H. LEWIS
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THE RELATION OF THESE EXPERIMENTS TO THE ANTERIOR LIMB
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It was found in most of these experiments that extirpation of myotomes, either the first, second, and third, the fourth, or the second, third, fourth and fifth, made no difference in the development of the musculatiu'e of the leg, even complete absence of these myotomes was not accompanied by defects in the musculature of the limb. In a few experiments, however, the anterior limbs were absent or defective or the development was retarded, probably due to extirpation along with the myotomes of all or some of the cells destined to form the limb rudiment. These experiments show then very conclusively that the musculature of the limb is not derived from the myotomes. The experiments were primarily directed toward this problem and the extirpation of the myotomes was done immediately after and in some cases even before separation of the myotomes in the limb region from the lateral mesoderm and before there was any chance for myotome processes to have entered the place where the limb was later to arise. These results agree with those of Byrnes^ on the relation of the limb muscles to the myotomes.
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We have seen from fig. 2, that in the normal development the myotome processes avoid the region of the pronephros and of the limb, and that it has been impossible to trace in a study of the normal development either myotome buds or cells into the limb bud.
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Both the experimental evidence and the study of the normal development support the idea that the musculature of the anterior limbs of Amblystoma develops in situ and is in no way derived from the myotomes or their ventral processes.
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^ Journ. of Morph. 1898. Vol. 14.
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Accepted by the Wistar Institute of Anatomy and Biology March 20, 1910. Printed June 6, 1910.
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LOCALIZATION AND REGENERATION IN THE NEURAL PLATE OF AMPHIBIAN EMBRYOS
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WARREN H. LEWIS From the AncUamical Laboratory, Johns Hopkins University
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. WITH ELEVEN FIGURES
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EXPERIMENTS ON RANA PALUSTRIS^
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It has already been shown that the dorsal and lateral lips of the blastopore of Rana palustris, when transplanted mto slightly older embryos, possess considerable powers of self-differentiation into chorda, muscle, and nervous tissue. At this early stage, chorda and muscle differentiate much more completely and normally than nervous tissue.* Evidently the cells in the lips of the blastopore destined to form nervous tissue possess to a limited extent only the power of self-differentiation when thus transplanted and removed form their normal environment, while the cells destined to from chorda and muscle have already attained greater powers of self-differentiation.' It is of course impossible at this early stage to distinguish in the lips of the blastopore by the ordinary histological methods the cells which are to form muscle from those that are to form chorda or nervous tissue. These experiments however indicate very clearly that there are very profound differences in the cells themselves apart from any environmental differences.
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All the embryos experimented upon, both Rana palustris and Amblystoma,
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were killed in Zenker's fluid, cut into serial sections, 10//. in thickness, and stained in hematoxylin and congo red.
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' Lewis, Experiments on the regeneration and differentiation of the central nervous system in Amphibian embryos. Am, Jour, of Anal., vol. 5, 1906. Preliminary note before the Am. Ass. of Anatomists. Dec. 27, 1905.
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' Lewis, Transplantation of the lips of the blastopore in Rana palustris, Am. Jour, of Anat.f vol. 7, 1907.
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192 WARREN H. LEWIS
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In another series of experiments on somewhat older gastrul© of Rana paltistris, small pieces were cut out anterior to the dorsal lip, from the region which later would form the anterior part of the neiu'al plate. Such pieces when transplanted into the mesenchyme in the otic region of an older embryo continue to differentiate into nervous tissue, with nuclear and reticular zones irregularly arranged. Small irregular ventricular spaces are sometimes found and nerves are often given ofif into the surrounding mesenchyme.^ Most of these embryos were killed twelve days after the operation, yet there is no indication of any degeneration of the transplanted tissue such as occurred in the nervous tissue in the preceding series. There has evidently been a considerable advance in the power of self-differentiation of this nervous tissue from that found in the lips of the blastopore of the earlier stage.
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In still older gastrulse of Rana palustriSj just before closure of the blastopore when the neural plate is faintly outlined, small pieces of the neural plate were cut out and transplanted into older embryos. Piece 3, (see fig. 1), from the region of the medulla, extending from the primitive groove part way to the neural fold was transplanted in such a manner as to be entirely siu'rounded by mesenchyme. The embryo was killed ten days after the operation and the sections show imbedded in the mesenchyme ventral to the otic vesicle a quite normal shaped medulla. A section through it is very similar to one through the normal medulla, (see fig. 2). This small unilateral transplanted piece has developed into a perfectly bilateral structm^e with a large ventricle and thin roof. Even the arrangement of the nuclear and reticular zones is bilateral and shows remarkable similarity to the arrangement in the section of normal medulla seen in the same figure. The transplanted piece becomes smaller at .either end and the ventricle is entirely closed. Had the piece remained in its original place in the neural plate it would probably have formed only a portion of one side of the medulla and have taken no part in the formation of the roof of the ventricle.
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Lewis, Am. Jour, oj AnaL, vol. 6, 1907, p. 469, figures 5 and 6.
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LOCALIZATION IN THE NEURAL PLATE
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193
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Piece 1, fig. 1, was transplanted in a similar manner and differentiated into what appears to be a somewhat irregular portion of the anterior end of the brain, with a small eye showing invagination and differentiation of the various layers of the retina. A nerve is given off from the caudal part of it. (figs. 3 and 4) .
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These two experiments alone are sufficient to indicate very clearly that the early neural plate of Rana palustris not only possesses great power of self-differentiation but that already there
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Fig. 1. — Outline neural plate Rana, pieces 1 and 3 transplanted.
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Fig. 2.— Section showing transplanted piece 3, ten days after transplantation, t, transplanted piece ; o, otic capsule.
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Figs. 3 and 4. — Sections through transplanted piece 1, thirteen days after transplantation.
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Fig. 5.— Outline of neural plate Amblystoma, pieces 1, 2, 3, 4 and 5, transplanted.
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is a localization in the various regions of cells or groups of cells that are destined to form certain parts of the central nervous system. The ordinary histological or microscopic examination of the neural plate does not reveal these differences yet the experiments show that a small piece from the region of the neural plate which one might expect from its location would form part of the medulla will do so whether it remains in the normal position or not.
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194
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WARREN H. LEWIS
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Not only do these pieces diflferentiate into certain specific parts of the neural tube but they regenerate some of the surrounding parts such as the roof of the ventricle and in some cases the opposite side. In the case of piece 3, fig. 1, which developed into the bilateal medulla-like structure (fig. 3) the piece was unilateral and did not extend to the edge of the neural plate so it must
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Fig. 6. — Section through transplanted piece 1, twenty-two days after transplantation.
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Fig. 7. — Section through transplanted piece 2, twenty-five days after transplantation.
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Fig. 8. — Section through transplanted piece 3, fifteen days after transplantation.
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Fig. 9. — Section through transplanted piece 4, fifteen days after transplantation.
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Fig. 10. — Section through transplanted piece 5, twenty-five days after transplantation.
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Fig. 11. — Neural plate Rana palustris showing area cut away. Total regeneration followed.
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have regenerated from itself the opposite half and the roof of the ventricle as well as some tissue on the same side. It has thus developed into a much more extensive piece than it would have, had it remained in the normal position. This would indicate that neighboring parts of the developing neural plate have under normal conditions a repressive influence on each other.
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LOCALIZATION IN THE NEURAL PLATE 195
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These transplanted pieces of the neural plate always close over to form a neural canal, the shape of the canal or ventricle varying with the region from which the piece is taken. The power of forming a neural canal then, resides within the neural plate itself or any portion of it and is not necessarily boimd up with mechanical influences from other parts of the embryo. In like manner the longitudinal foldings of the brain, its flexures or bends, are probably due to intrinsic factors within the brain itself. The transplanted piece 1, shows indications of this process.
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EXPERIMENTS ON THE NEURAL PLATE OF AMBLYSTOMA
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PUNCTATUM
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The results obtained from many experiments on Amblystoma are similar to those from Rana pahtstris. As in the experiments on Rana palustris small pieces of the neural plate were cut out and transplanted into the otic region of somewhat older embryos. About one hundred and fifty such pieces were transplanted from the neural plates of twenty-seven different embryos. Two to eight pieces from each plate.
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Pieces were taken from practically every region of the neural plate, and were allowed to develop in the transplanted position from ten to twenty-five days. At the time of transplantation there is no indication, other than general topographical position, of the different regions of the central nervous system. The histological picture of the arrangement and of the character of the cells is practically the same throughout the neural plate and only in later stages does the arrangement become characteristic for each portion of the central nervous system.
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Fig. 5, for example, shows the position of five pieces which were cut out of the neural plate and transplanted into the otic region of an older embryo of Amblystoma. Figs. 6, 7, 8, 9 and 10, are from sections through these pieces — 1, 2, 3, 4 and 5 respectively, which were allowed to develop for a number of days after the transplantation. Each piece has developed into a more or less characteristic form, corresponding somewhat to sections through the normal brain, medulla and upper part of the spinal cord. After the study of a number of such pieces and comparison
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196 WARREN H. LEWIS
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of them with sections through the normal central nervous system it was possible, without knowing beforehand from which region of the neural plate the piece was taken, to tell quite accurately its original location.
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In normal embryos killed twelve days or more after the neiu-al plate stage, transverse sections through the various regions of the brain and cord are very characteristic for each region, not only in the general outline and shape of the outer surface and ventricle but in the arrangement of the nuclear and reticular zones as well.
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The transplanted pieces always close in to form the neural canal or ventricle. The form of the external surface of the canal (ventricle), and of the walls varying according to the region from which the piece was taken. Each piece seems to develop into that portion of the central nervous system into which it would have developed had it remained in the normal position. Not only does this take place but there is to a certain extent regeneration of the opposite side.
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In the region of the medulla and spinal cord this regeneration sometimes results in a bilateral structure developing from a unilateral piece. All the transplanted pieces were unilateral at the time of transplantation.
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Since each piece develops into a tube-like structure no matter what its orientation may be in its strange environment, the indication is very clear that this process is dependent only on changes which go on within the piece itself. We can correctly infer from this that the rolling in of the entire neural plate, to form the tubular central nervous system, is dependent only on changes which take place within the neural plate itself and is thus quite independent of influences from the rest of the embryo.
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Again, since each piece appears to develop into that portion of the central nervous system into which it would have developed had it remained in its normal position, we must conclude that at this stage every part of the neural plate possesses the power of self-diflferentiation and is not dependent either upon influences of other portions of the embryo or of neighboring parts of the medullary plate itself for its differentiation. The neighboring regions, however, do influence each other in a way in regulating
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LOCALIZATION IN THE NEURAL PLATE 197
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the development by preventing such regions from that additional growth which they show after transplantation, such as regeneration of a portion of the opposite side or the formation of a roof to the ventricle, etc.
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REGENERATION
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The preceding experiments have shown that even a small piece of the neiu-al plate possesses great regenerative power when cut out and transplanted into a strange environment. Likewise the neural plate itself has the power of regenerating small areas that have been removed.
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One of my pupils, Mr. Dirge, removed a considerable portion of the floor at the anterior end of the neural plate on one side of the median line in Rana palitstris. We were not aware at the time, of the power of regeneration and had hoped to remove permanently that portion of the brain which gave rise to some of the cranial nerves supplying the eye muscles of one side of the head. It was found however that even after as large a piece as is represented by the shaded area in figure 11 was removed regeneration is practically complete and so far as one can judge from serial sections the brain after two or three weeks is perfectly normal, bilateral and all the cranial nerves are present. This was repeated on a number of embryos of this stage with the same result. In some embryos however, when considerable degeneration and disintegration of the tissue about the wound followed the operation, there was often imperfect regeneration on this side of the brain. There is evidently then a limit to the power of regeneration of lost parts of the brain at this stage but within certain limits regeneration is complete.
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In a number of my experiments on the transplantation of the optic vesicle a portion of the adjoining brain wall was transplanted with the optic vesicle. In the majority of these experiments the piece transplanted was not very large and regeneration of the lost part was complete. In a few, however, where larger pieces were transplanted with the optic vesicle the brain in the region
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198 WARREN H. LEWIS
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from which the piece was taken did not succeed in regenerating the lost part entirely and shows defect on that side. In all embryos, however, the ventricle becomes closed, the thickness of the defective wall varying more or less with the size of the piece removed.
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Accepted by the Wistar Institute of Anatomy and Biology March 20, 1910. Printed June 6, 1910.
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THE STAINING OF FATS IN EPITHELIUM AND MUSCLE FIBERS^
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E. T. BELL
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From the Anatomical Laboratory* University of Missouri
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If a section of kidney be examined fresh in aqueous humor the cells of the convoluted tubules will usually be seen to contain a large number of small, more or less refractive droplets. If the section be cleared a few minutes in dilute potassium hydroxide the droplets become much more sharply defined and a great many more may be distinguished. The same procedure will show a large number of droplets in the Uver, striated muscle, and other tissues. The droplets in the muscle fibers are the interstitial granules described by KoUiker, Knoll, Schaflfer, and others; those in the Uver, kidney, etc. are not so well-known. Albrecht has called the droplets demonstrable in this way liposomes (Liposomen).' Because of the convenience of this term it seems advisable to adopt it, although these droplets do not always consist entirely of lipoids. Some of the droplets are strongly refractive; others are only faintly refractive, but there are all gradations between these two types. The strongly-refractive droplets are in most cases the ordinary fat droplets; the others consist in part at least of lipoid substances.
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' Presented at the 25th Session of the Amer. Ass. Anat., Boston, December, 1909.
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' The Department of Anatomy is cooperating with the Missouri Agricultural Experiment Station in the study of the process of fattening. The present paper is one of a series published in connection with this work.
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' The term "liposome" will be used in this paper to mean those refractive droplets, visible in fresh tissue after the above mentioned treatment, which may be stained with Herxheimer's scarlet red. After a brief exposure in absolute alcohol the liposomes can no longer be shown by a fat stain.
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THE ANATOMICAL BECOBD, \oI. 4, NO. 5.
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200 E. T. BELL
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It is the purpose of this communication to show that the liposomes may be readily stained, in fresh tissues with Herxheimer's scarlet red, and to call attention to some differences among them in staining properties and susceptibility to fixing reagents. Osmic acid and the simple alcoholic solutions of scarlet red and sudan will stain many of the liposomes, sometimes all of them; but in many tissues crowded with these structures, the stains just mentioned give negative results, when the alkaline-alcohoUc scarlet red (Herxheimer's stain) gives decidedly positive results. By the use of Herxheimer's stain on fresh tissues it is easy to study the nature and distribution of the liposomes and their variations under different nutritive conditions. These results were mentioned briefly in the Appendix of a previous paper (6, p. 435). At that time I had very unsatisfactory results with Herxheimer's stain, and thought that the alkaUne-alcoholic solutions of scarlet red prepared by Bullard were much better; but I have learned since that Herxheimer's stain, when used properly, is usually as good.
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The technique used for the demonstration of ordinary fats seldom stains all the Uposomes in a tissue. To demonstrate the ordinary fats, it is usually recommended that the tissue be fixed first in formalin. Frozen sections are then to be cut and stained with osmic acid, sudan, or scarlet red. A fat stain extensively used at present is a saturated solution of scarlet red prepared by dissolving the dye in boiling 70 to 85 per cent alcohol (Fischer's method). In order to stain all the fatty droplets, two essential changes must be made in the above-mentioned technique. (1) The tissues must be stained fresh. No fixatives are to be used. (2) The alkahne-alcoholic scarlet red (Herxheimer's stain) must be used.
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The tissues examined have been mainly those of the calf, cat, dog, rat and frog. Some of the voluntary muscles were examined in all cases. Usually the kidneys and heart and sometimes the liver were studied. Frozen sections of the fresh tissues were examined as follows: (a) unstained in aqueous humor, normal salt, 1 per cent acetic acid, 1 to 5 per cent potassium hydroxide; (6) after staining in 1 per cent osmic acid; (c) after
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THE STAINING OF PATS 201
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staining with simple alcoholic solutions of scarlet red, i.e., saturated solutions prepared by dissolving the dye in boiling 70 to 85 per cent alcohol; (d) after staining with alkaline-alcoholic solutions of scarlet red (Herxheimer's stain). Some of the sections were usually preserved in 55 to 70 per cent alcohol, 10 per cent formalin, potassium bichromate, etc. before staining, to determine the effect of the fixatives.
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Examination of fresh material. If frozen sections of fresh striated muscle be examined in normal salt solution the interstitial granules are readily seen arranged in longitudinal rows between the fibrils. Rather more granules may be seen if the muscle be teased fresh in aqueous humor. Still more of the finer granules are visible if the tissue be cleared in dilute potassium hydroxide. The granules vary greatly in size. As a rule the larger ones are sharply refractive and the smaller ones weakly-refractive, but often this distinction does not hold. Droplets of ordinary neutral fat may be distinguished by their being more refractive than any others. 1 per cent acetic acid apparently does not dissolve the granules but it often causes the weakly-refractive ones to become indistinguishable from the sarcoplasm in which they lie; the more refractive granules are not affected. These interstitial granules are Albrecht's liposomes. The first accurate description of them was given by Kolliker (18).
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Two types of muscle fibers may usually be distinguished — the so-called dark and light fibers. The dark fibers are crowded with liposomes; the light fibers usually contain only a few. A dark fiber may contain a comparatively few coarse droplets or a large number of small ones; the light fibers may contain a large number of small, very faintly refractive droplets. All possible intermediate forms between typical dark and light fibers may be seen in some muscles. The proportion of dark fibers to light fibers varies in different species and in the different muscles of the individual. It also depends to some extent upon the age and nutritive condition of the animal. Often two types of fibers can hardly be distinguished. The distribution of the dark and light fibers has been described by Griitzner (11), Knoll (17), Schaffer (19), and others for a large number of animals. It is clear from the work of
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202 E. T. BELL
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these observers that the darkness or cloudiness of the fibers is due in part at least to the presence of the interstitial granules, but this is not the only factor involved, since the dark fibers still appear decidedly darker than the light ones even after the interstitial granules have been dissolved out or rendered invisible. The above-mentioned investigators did not recognize the fatty nature of the interstitial granules except in those cases where they may be stained with osmic acid, sudan and scarlet red not being known at that time. As far as I have observed the granules are all isotropic, but I have not studied this point extensively.
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In the kidney, as in the muscles, some of the liposomes are visible in aqueous humor and normal salt solution. Dilute potassimn hydroxide shows them most clearly. After treatment with 1 per cent acetic acid the faintly-refractive liposomes are no longer visible, but the strongly-refractive ones are unaffected. The strongly-refractive Uposomes, as in muscle, are apparently the ordinary fat droplets and may be demonstrated by the ordinary technique, i.e., by fixation in formalin and staining in osmic acid or simple alcoholic scarlet red. The Uposomes occur mainly in the secretory portions of the renal tubules; they are not so numerous in the clear protoplasm of the collecting tubules. In some tubules in the section no liposomes at all can be demonstrated. The amoimt of ordinary fat in the kidney varies greatly. Of the animals examined, the cat shows the greatest amount of fat in this organ; the ox, the least. Both the less refractive liposomes and the more refractive (ordinary fat droplets) may be found in a cross section of the same renal tubule, though usually only one kind is present.
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The liver often contains a large number of strongly-refractive liposomes (ordinary fat droplets) which replace or obsciu'e the less refractive liposomes. Livers in which there is little or no ordinary fat are best adapted for the study of the less refractive droplets.
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Staining vxiih osmic acid. Altmann (4) has shown that osmic acid is reduced by oleic acid and triolein, but not by tripalmatin, tristearin, or their acids. This has been very generally accepted; but Starke (20) and a few others maintain that osmic acid will
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THE STAINING OP FATS 203
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blacken all the fat if the sections be kept in alcohol for some time after the osmic treatment. Starke found that out of 150 frogs (Rana esculenta) there were only two in which the fat in the liver was blackened directly by osmic acid; in all the others it became black only after the osmic-alcohol treatment. These results together with some tests with supposedly pure fats led him to the conclusion that palmatin and stearin are blackened by the osmic-alcohol method. He beUeves that oleic fats are blackened directly by osmic acid and that palmatin and stearin are colored yellowish or brown but become black if kept in alcohol for some time after the alcohol treatment.
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Handwerck (12) agrees with Starke that the osmic-alcohol reduction takes place in the tissues but does not accept his explanation. According to Handwerck pure palmatin and stearin do not give the secondary reduction in alcohol; but if a sUght trace of olein be added some blackening may be obtained. Osmic acid is a very delicate reagent for oleic fats.
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Heidenhain (13), rejects the osmic-alcohol treatment on the ground that it blackens some structures that are not fat and fails to blacken some that undoubtedly are.
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The extent to which osmic acid stains the Uposomes depends probably upon their chemical composition. Sometimes (muscles of one adult rat, and one adult dog) it blackened every droplet that could be shown by any other method; in other instances however (muscles of two calves, one adult dog, five sucldng pups; parts of the kidney in most animals, etc.) it gave no color at all to any of the Uposomes, though they were easily stained in these cases with Herxheimer's solution. Sometimes (muscles of rat, kidney of cat, etc.) the simple osmic treatment may give the Uposomes a brown color which changes to black if the sections be washed in water and kept 24 hours in 80 per cent alcohol (Starke's method). But the secondary treatment in 80 per cent alcohol may remove the color completely in a short time. This was found to be the case in the muscles of an emaciated cat, two sucking pups, and several rats. 80 per cent alcohol dissolves a great many of the less refractive Uposomes after an exposure of a few hours. Even 60 per cent alcohol may produce the same result. In two
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204 E. T. BELL
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instances (one pup and one rat) the liposomes of the muscles were nearly all colored brown by osmic acid. The sections were then washed with water and put in 60 per cent alcohol. The droplets were nearly all decolorized after an exposure of thirty minutes in this solution. On the whole osmic acid is a useful reagent for the study of the liposomes. It often gives a brown color to droplets not stained at all by the simple alcoholic solutions of scarlet red and sudan.
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In some instances (muscles, kidney, and liver of some rats) excellent results were obtained by fixation in Altman's fluid. The sections were washed 24 hours, dehydrated rapidly, cleared in cedar oil, and embedded in paraflSn. Thin sections were cut and examined in cedar oil. This method has the advantage that thin sections may be had and the nuclei and boundaries of the cells may be seen much better than in frozen sections; but, as pointed out above, many liposomes cannot be stained at all with osmic acid especially those that are very faintly refractive.
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As to the chemical composition of the droplets that may be shown with osmic acid, it is known that the unsaturated neutral fats are stained black; but the large number of liposomes which stain brown or grey cannot be identified with certainty.
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Simple alcoholic solutions of scarlet red. Daddi reconamended a saturated solution of sudan in 96 per cent alcohol, but alcohol of this strength was found to dissolve some of the fat, so that solutions in the weaker alcohols soon came to be preferred. The stains in use for a long time were saturated solutions of sudan or scarlet red prepared by dissolving the dye in cold 70 to 85 per cent alcohol. These stains are very weak.
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A decided improvement was made by Fischer (10) who suggested dissolving the dye in boiling alcohol. This solution is considerably stronger than those made with cold alcohol and it seem>s to be extensively used at the present time. Traina (21) prepared a saturated solution of scarlet red in 70 per cent alcohol and kept it with excess of the dye in an oven at 40° C for two weeks before using. This seems to be of about the same strength as Fiscner's solution. Scarlet red is usually to be preferred to sudan because of the brighter color it gives to fat droplets after relatively short exposure.
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THE STAINING OF FATS 205
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For staining ordinary fat droplets Fischer's and Traina's stains are usually satisfactory, but they seldom stain any of the faintlyrefractive liposomes. In. the muscles of some of the cats and dogs examined, they stained all the liposomes; but in a great many instances they stained only a very few of the liposomes or none of them at all. The muscle fibers of five sucking pups, two young calves, and several of the rats were full of coarse droplets that stained readily with Herxheimer's stain but were not colored at all by the simple alcoholic stains. Some liposomes which are browned by osmic acid are not colored at all by these stains, and on the other hand the simple alcoholic stains are said in some cases to stain liposomes that osmic acid does not affect.
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The simple alcoholic solutions of scarlet red and sudan are also very variable in their actions. Considerably more fat is often shown if the staining dish is not too tightly closed. If a very small amount of evaporation is allowed the stain is somewhat more effective. Care was taken to exclude precipitates in these cases by comparison with sections stained by other methods and with unstained sections in normal salt and dilute potassium hydroxide.
 +
 +
Alkaline-alcoholic scarlet red {Herxheimer^s stain). This solution may be prepared by dissolving two grams of sodium hydroxide in 100 cc. of 70 per cent alcohol. Scarlet red is then to be added to saturation. The solution should not be heated. Alkaline-alcohol dissolves considerably more of the dye than does ordinary alcohol. This solution is therefore much stronger, and it is more effective than any other fat stain. Herxheimer (15) claimed for his solution that it would stain more intensely than simple alcohoHc scarlet red, but he does not state definitely that it will stain any droplets not stained by the latter. He however quotes Erdheim (9) as having found droplets in the thyroid which could be stained by the alkaline but not by the simple alcoholic solution. This statement of Erdheim's is the only one known to me in the literature in which it is claimed that Herxheimer's solution will stain droplets not shown by any other fat stain.
 +
 +
H. H. Bullard in some work done in the Anatomical Laboratory
 +
 +
 +
206 E. T. BELL
 +
 +
at the University of Missouri, first showed clearly the great superiority of the alkaline solutions. His results have not yet been published.
 +
 +
One of the strongest objections made against Herxheimer's stain is its tendency to form precipitates. It is claimed by Fischer, Traina, and others that the stain is inferior to the simple alcoholic solutions on this account mainly. This objection is indeed well-founded in some instances. Freshly-prepared solutions (less than one day old) are of ten worthless on this account; and this tendency to form precipitates may persist in older solutions. But usually solutions a few days old give no trouble at all in this respect. A stain should not be used if it forms precipitates.
 +
 +
To determine whether any given stain forms precipitates, a section may be put in a hoUow-ground slide with a few drops of the stain. A cover glass is then sealed over it quickly to prevent evaporation. One may then watch the droplets stain under the microscope. A precipitate may be detected in this way as soon as it begins to form. The character of the precipitate of any solution may be studied by allowing it to form on a section and then examining it under high magnification. The small dark granules of the precipitate may often be readily distinguished from the Ughter colored liposomes, so that even under these conditions there is no confusion. But in every doubtful case the stained section should be compared closely with fresh sections mounted in normal salt solution or dilute potassium hydroxide.
 +
 +
After staining, the sections should be washed in 60 per cent alcohol about thirty seconds ajid then transferred at once to distilled water to wash out the alcohol. After a few minutes in distilled water they may be mounted in glycerin. If the alcohol is not washed out the sections are decolorized in a short time. The staining may be done in small tightly-stoppered vials.
 +
 +
Herxheimer's solution stains apparently all the droplets which may be demonstrated with dilute potassium hydroxide in a fresh tissue. It stains with varying degrees of intensity. The stronglyrefractive droplets stain an intense red, the faintly-refractive droplets, a faint red; but there are all gradations between these
 +
 +
 +
THE STAINING OF FATS 207
 +
 +
two types. Sometimes fine faintly-tinged droplets can be shown which are not visible in the potassium hydroxide preparations. The differences in intensity of staining among the Uposomes may be due to the kind or the amount of the lipoid substances present, or both these factors may be involved.
 +
 +
Staining with neutral red. Albrecht (1) states that if tissues be kept in sterile vessels at 37° C for twenty-four hours, the Uposomes will then stain with neutral red and show myelin figures in polarized light. Muscle must be kept in normal salt solution under otherwise similar conditions to give the same result. He holds that if muscle be treated as above described it will show longitudinal rows of droplets between the fibrils, which stain with neutral red and show myelin figures. These droplets are supposed to be identical with those seen in fresh tissues.
 +
 +
Albrecht (3) states also that if fresh muscle be mounted in 5 per cent potassium hydroxide the Uposomes are shown very clearly, and if the tissue be kept in this solution a few hours they show myeUn figures. Albrecht calls those droplets which show myelin figures only after being kept several hours at body temperature, postmortem myelin, to distinguish them from those which show myelin figures in the Uving tissue (intravital myelin).
 +
 +
In several rats, free-hand sections of the kidney were cut immediately after death and stained in a 1:10,000 neutral red solution at 37° C for about one hour. The convoluted tubules were shown full of coarse deeply-stained droplets. The size and arrangement of these droplets show that they cannot to any considerable extent correspond to the Uposomes. In one rat kidney a number of tubules, which did not show any Uposomes at all, were shown fuU of coarse droplets by neutral red. I have not succeeded in staining any granules in muscle with neutral red.
 +
 +
Several times I have repeated Albrecht's experiment of keeping the kidney (in this case that of a rat) in a sterile vessel at 37° C for twenty-four hours after removal from the body. A large number of droplets showing myeUn figures are to be seen, but they do not seem to me to correspond at all to the Uposomes seen in the fresh tissue. The numerous small Uposomes seen in the fresh tissue have all disappeared.
 +
 +
 +
208 E. T. BELL
 +
 +
Effect of fixation. To test the effect of fixatives frozen sections were cut and put directly into them. The effect may be more rapid by this method than that obtained by the fixation of a block of tissue.
 +
 +
Ten per cent formalin. A considerable part of the droplets in the muscle fibers of many adult cats and dogs are unaffected by an exposure of several months or more in this solution. The same is true for a great many droplets in the liver, kidney, and other organs. The droplets unaffected by this solution are usually strongly refractive and may usually be demonstrated by the ordinary fat stains. They are presumably droplets of ordinary neutral fat.
 +
 +
In other cases there is a gradual loss of the fat when the tissue is preserved in this solution. The gastrocnemius of a kitten, which contained a large amount of fat when examined fresh, gradually lost fat until at the end of a week only a few coarse droplets could be demonstrated.
 +
 +
The gastrocnemii of six sucking pups were also examined. When stained fresh in Herxheimer's stain, nearly every fiber showed several coarse droplets in a cross section. In four of the pups the droplets stained brown in osmic acid, but the color disappeared after a short time in alcohol or glycerin; 80 per cent scarlet red stained only a few droplets. In these four pups a great many droplets in the muscle fibers were lost after an exposure of only thirty minutes in formalin, and after twenty-four hours in this solution only a few droplets could be stained. In the other two pups the droplets stained readily with all the fat stains and were not affected by an exposure of ten days or longer in formalin.
 +
 +
The muscle fibers of two adult dogs, two young calves, and a number of rats were found to contain a large number of liposomes which were gradually rendered unstainable in formalin. Most of the droplets were lost to the stain after one to five days in the fixative. The liposomes of the muscles of an emaciated cat were affected in the same way.
 +
 +
The faintly-refractive liposomes of the kidney are nearly all lost after one day or less in formalin. The droplets that stain black with osmic acid and deep red with simple alcoholic scarlet
 +
 +
 +
THE STAINING OF FATS 209
 +
 +
red are not much affected by any of the fixatives, but a few hours in formalin is usually sufficient to render the weakly-refractive droplets unstainable.
 +
 +
55 to 70 per cent alcohol acts upon the liposomes in about the same way and somewhat more rapidly than formalin. Eighty per cent alcohol dissolves the faintly-refractive liposomes very rapidly.
 +
 +
Potassium bichromate is decidedlj'^ less rapid in its action than either alcohol or formalin but ultimately produces about the same result. Ciaccio (7, 8) preserves tissues in a formalin-bichromate acetic mixture which he believes fixes the lecithin so that it is not removed by the ordinary fat solvents. The tissues are taken through xylol into paraffin so that the ordinary fat droplets are dissolved out. The sections are stained on the slide with simple alcoholic sudan. I have made only a few observations with this fixative. A few of the coarse liposomes are apparently fixed by this fluid and may be colored a light orange with simple alcoholic Sudan after the sections have passed through the fat solvents. But I believe with AschofT (5) that it is not proved that the droplets in question are really lecithin.
 +
 +
It will be apparent from the foregoing remarks that when a piece of muscle or kidney is fixed in formalin, alcohol, potassium bichromate, etc., some of the liposomes are usually removed or rendered invisible. The number of liposomes lost varies in different individuals as well as in different species. Pups of the same litter may contain entirely different fats. The effect of the fixative also varies with the age and nutritive condition of the animal and the length of time it acts upon the tissue. The action of the fixative in one tissue may be unappreciable for weeks, and in another nearly all the liposomes may be removed in a few minutes. The action of all the fixatives is particularly rapid on fine droplets that are difficult to stain, such as those of the heart. Probably the varying effect of the fixative is due to the varying chemical composition of the liposomes.
 +
 +
Solubility. The liposomes are all readily soluble in absolute alcohol and ether. Weaker alcohols dissolve the faintly-refractive liposomes with varying degrees of rapidity. The statement that
 +
 +
 +
210 E. T. BELL
 +
 +
the liposomes are dissolved in these fluids means only that they can no longer be demonstrated with the fat stains.* It is probable that some of the liposomes are only in part composed of lipoids and that in these cases only the fatty portion of the liposomes has been removed. When fixed tissues are treated with 5 per cent potassium hydroxide no more liposomes are shown than can be stained with Herxheimer's solution. To determine whether the liposomes have been removed from a muscle fiber, longitudinal sections should be examined, since the masses of sarcoplasm seen in cross section between the fibrils may simulate them closely. Albrecht believed that many of the liposomes contained only an external lipoid layer, while the central core was of a non-fatty character.
 +
 +
Relation of the liposomes to the nutritive condition of the animal. Knoll, (16) in the heart muscle of pigeons starved six to nine days, found that the droplets visible in the fresh tissue were much fewer and that by far the majority of these were faintly refractive. The strongly-refractive droplets were greatly diminished by starvation. My observations corroborate KnolFs. Several rats which were kept on low rations until they had lost over twenty per cent of their body weight showed the muscle fibers free from liposomes. An adult cat which had lost about the same per cent of its body weight showed only faintly-refractive liposomes in the muscle fibers. The ordinary fat droplets in the kidney were not removed in these animals. Apparently the ordinary fat droplets are removed from the muscle fibers in the earUer stages of hunger, and the faintly-refractive droplets in the late stages. My observations are, however, not extensive enough yet to justify this as a general conclusion. The relation of the liposomes to the nutritive condition is a promising problem for future investigation.
 +
 +
^ In a few instances some of the interstitial granules of the muscle fibers were shown by 5 per cent potossium hydroxid after having been exposed to absolute alcohol for forty-eight hours. They were not as large as before and could not be stained by any fat stain. It is therefore evident that these granules consisted only in part of lipoids and that the lipoid portion was dissolved by the alcohol.
 +
 +
 +
THE STAINING OF FATS 211
 +
 +
SUMMARY.
 +
 +
The protoplasm of renal cells, muscle fibers, etc., shows usually a large number of small more or less refractive droplets (liposomes) when examined in aqueous humor, or dilute potassium hydroxide.
 +
 +
These liposomes may all be stained with Herxheimer's scarlet red if fresh tissues are used.
 +
 +
All the liposomes disappear after a short exposure to absolute alcohol; and the weaker alcohols remove the faintly-refractive liposomes more or less rapidly.
 +
 +
Preservation of the tissues in formalin, alcohol, potassium bichromate, etc., may affect a large per cent of the liposomes so that they can no longer be stained. The effect of the fixative may be very pronounced in a few minutes, or it may require several days to produce noticeable changes.
 +
 +
The evidence cited in the preceding pages seems sufficient to prove that the liposomes consist wholly or in part of Upoid substances.
 +
 +
The staining of the lipoids with Herxheimer's scarlet red is a simple and accurate method for the further study of their character and distribution and their relations to cell metabolism.
 +
 +
BIBLIOGRAPHY.
 +
 +
1. Albrecht, £. Neue Beitr&ge zur Pathologie der Zelle. Deutsche path. GeaeU 1902 achaft, 5.
 +
 +
2. 1903 Ueber triibe Schwellung und Fettdegeneration. Deutsche path. QaeelU
 +
 +
schaftf 6.
 +
 +
3. 1903 Ueber die Bedeutung myelinogener Substanzen im Zellleben.
 +
 +
Deutsche path, Gesellschaft, 6.
 +
 +
4. Altmann, R. Die Elementarorganismen, S. 98.
 +
 +
1894.
 +
 +
5. AscHOFF, L. Zur Morphologie der lipoiden Substanzen. Ziegler^s Beitrdge,
 +
 +
1909 Bd. 47, H. 1.
 +
 +
6. Bell, £. T. On the occurrence of fat in the epithelium, cartilage, and
 +
 +
1909 muscle fibers of the ox. Amer. Journal ot Anatomy y vol. 9.
 +
 +
7. CiACCio, C. Beitrag zum Studium der Zelllipoide in normalen und patholo 1909 gischen Verh&ltnissen und einer besonderer Entartung vom lipo idem Typus (lecithinische Entartung). CentraWlattf. allg. Path, u. path, Anat, Bd. 20, Nr. 17.
 +
 +
 +
212 E. T. BELL
 +
 +
8. 1909 Ueber das Vorkommen von Lecithin in den zellularen Entztindungs produkten und iiber besondere lipoidbildende Zellen (Lecithinzellen). Centralblatt f. allg. Path. u. path. Anat. Bd. 20, Nr. 9.
 +
 +
9. ErdheiM; J. Zur norm. u. path. Histologie der Glandula thyreoidea, para 1903 thyroidea, u. Hypophysis. Ziegler's Beitrdge Bd. 33.
 +
 +
10. Fischer, B. Ueber die Fettfarbung mit Sudan III und ScharlachR. Cen 1902 tralblati f. allg. Path, u path. Anat., Bd., 13.
 +
 +
11. GRtJTZNER. Zur Physiologie und Histologie der Skelettmuskeln. Brealauer
 +
 +
1886-'86 artzliche Zeitschrift.
 +
 +
12. Handwerck, C. Beitrage zur Kenntnis vom Verhalten der Fettk6rper zu
 +
 +
1898 Osmiumsaure und zu Sudan. Zeitschrift fur wissenschaftliche
 +
 +
Mikroskopiey Bd. 15.
 +
 +
13. Heidenhain, M., Plasma und Zelle. Jena, S. 428.
 +
 +
1907
 +
 +
14. Herxheimer, G. Ueber FettfarbstoflPe. Deutsche med.Wochen8chriftyS.G07.
 +
 +
1901
 +
 +
15. 1904 Ueber **Fett-Infiltration" und * 'Degeneration." Lubarsch-Ost^r tag: Ergebnisse der allg. Path, und path. Anatomie, 8.
 +
 +
16. Knoll, P. Ueber Myocarditis und die tibrigen Folgen der Vagussection bei
 +
 +
1880-81 Tauben. Zeitschrift fur Heilkunde, Bd. 1.
 +
 +
17. 1891 Ueber protoplasmaarme und protoplasmareiche Muskulatur.
 +
 +
Denkschriften der kaiserl. Akad., mathem. naturw. Cl.y Wien, Bd. 58.
 +
 +
18. K5LUKER. Gewebelehre, 6 Aufl. Bd. I, S. 140. 1889
 +
 +
19. ScHAFFER, J. Beitrage zur Histologie und Histogenese der quergestreiften
 +
 +
1893 Muskelf asern des Menschen und einiger Wirbelthiere. Sitzungs bericht. d. kaiserl. Akad. d.WissenschafteninWien. Mathem. naturw. CI.; Bd. CII, Abth. 3.
 +
 +
20. Starke, J. Fettgranula und eine besondere Eigenschaft des Osmiumtetra 1895 oxydes. Archiv f. Physiologie.
 +
 +
21. Traina, R. Ueber das Verhalten des Fettes und der Zellgranula bei chron 1904 ischem Marasmus und Hungerzustanden. Ziegler's Beitrdge, Bd. 35.
 +
 +
 +
THE EFFECTS OF VARIOUS FIXATIVES ON THE BRAIN OF THE ALBINO RAT, WITH AN ACCOUNT OF A METHOD OF PREPARING THIS MATERIAL FOR A STUDY OF THE CELLS IN THE CORTEX
 +
 +
HELEN DEAN KING Associate in Anatomy at the Wistar Institute
 +
 +
WITH FIFTEEN FIGURES
 +
 +
While endeavoring to obtain preparations of the brain of the albino rat (Mus norvegicus var. albus) that would be suitable for a study of the cells in the cerebral cortex I have had occasion, this past year, to investigate the histological changes produced in this material by various methods of fixation and of imbedding: the results of this investigation are given in the present paper. There are but few observations regarding the histological action of different fixatives on brain tissue, and none of the recorded investigations dealing with the effects of various preservatives on the weight and volume of the brains of mammals have been accompanied by an account of the structural changes these preservatives produce.
 +
 +
According to the observations of Donaldson ('94), of Hrdlicka ('06), and of Fish ('93), the age and physical condition of an animal, the length of time it has been dead before the brain is put into the fixing fluid, the amount of fluid used and the temperature at which it acts, are all factors which tend to produce variations in the weight and volume of the brain. In all of the experiments on the brain of the albino rat which are recorded in the present paper an effort was made to eliminate as many as possible of the factors which might be supposed to influence the results. The animal selected for each experiment was one that was presumably in a healthy condition. It was killed either by ether or by illuminating gas
 +
 +
THB ANATOyiCAL RBCORD. VOL. 4, KO. 0.
 +
 +
 +
214 HELEN DEAN KING
 +
 +
and then weighed and measured. The bram was taken out as soon as possible after the death of the animal and placed on absorbent cotton in 40 cc. of the fixing solution whose action was to be tested. Except in one case (rat no. 5), all fixation was done at room temperature which was about 20°C. The brains of adult individuals were taken for all of the experiments but two (rats nos. 20 and 21). The exact age of the animal used was not known in aiiy case; but this factor could have had little, if any, influence on the results, as none of the rats could have been over a year old and the majority of them were much younger. The physical condition of the animals, therefore, is the uncontrolled factor which might have affected the results, and to it can doubtless be ascribed the variations in the results which were obtained when braiiiS of different individuals were subjected to similar treatment.
 +
 +
After remaining in the fixing fluid a given length of time, each brain was drained for a moment on filter paper, to remove the superfluous liquid, and then carefully weighed in a closed weighing bottle. After passing through the various grades of alcohol required by the method of fixation employed, the brains were brought into 70 per cent alcohol, where they remained for fortyeight hours. They were then drained and weighed a second time in order to determine the loss in weight due to the replacement of the water in the brain by alcohol.
 +
 +
In all of the earlier experiments the brains were divided longitudinally after they had been weighed a second time, and each half of the brain was imbedded by a different method in order to ascertain what structural changes could be attributed to the process of imbedding when the same methods of fixation had been employed. It was soon found that methods of imbedding commonl}^ used for neurological material, as well as for other tissues, produce marked alterations in the structure of the cells' in the cerebral cortex. Imbedding in paraffine after clearing with either xylol, oil of cedar, bergamot oil, or chloroform, does not give satisfactory preparations of the rat's brain when the details of cell structure are wanted. Celloidin, since it can be used without heat, is a very excellent medium for imbedding brain tissue. There are, however, several disadvantages connected with the
 +
 +
 +
EFFECTS OF FIXATIVES ON RATS' BRAINS 215
 +
 +
use of celloidin as an imbedding medium, not the least of which is the difficulty of obtaining unbroken series of very thin sections. Equally good results were obtained when brains were imbedded in celloidin according to the methods advocated by Hardesty (^02) and by Lee ('05) as when the very long method devised by Miller ('03) was employed. After experiments had been made with a number of different methods it was finally decided that the most satisfactory results were obtained by double imbedding in celloidin and paraffine according to the method of Bodeker C08). The details of this method are given in the second section of this paper.
 +
 +
For convenience in description, the data collected in the course of this study are given in six tables. In each of the first five tables the first column gives the index numbers of the rats whose brains were used, while the second column denotes the solutions used for fixation. The next two columns show the weight of each brain on its removal from the fixing solution, together with the percentage gain or loss in weight as a result of the action of the solution; the computed weight of the fresh brain being taken as the standard. The fifth column gives the weight of each brain after it had remained in 70 per cent, alcohol for forty-eight hours; and the last column shows the percentage gain or loss in weight as a result of the replacement of the water in the brain by alcohol. All of the data are brought together in table 6 which gives for each rat, in addition to what is shown in the first five tables, the sex, body weight, body length, the length of time the brain remained in the fixing solution, and also the weight of the fresh brain as computed from body length and body weight according to the method given by Donaldson ('08, '09), which is based on formulas devised by Hatai ('08, '09). [See page 233.]
 +
 +
With the few exceptions noted, all brains were imbedded in celloidin or in celloidin-paraffine. Sections were stained with thionin, except in the two cases (rats nos. 43 and 44), where this stain did not give satisfactory results. The illustrations are from drawings of the large pyramidal cells in the cerebral cortex taken from frontal sections at the level of the optic chiasma. As far as possible cells were selected for drawing which represented the
 +
 +
 +
216
 +
 +
 +
 +
HELEN DEAN KING
 +
 +
 +
 +
average condition of the large cortex cells, after the brains had been subjected to a given course of treatment. In the various tables a star (*) is prefixed to the index number of each rat from whose brain cells were selected for illustration.
 +
 +
A. THE EFFECTS OF VARIOUS FIXATIVES ON THE BRAIN OF THE ALBINO RAT
 +
 +
At the present time formaldehyde is very generally used for the fixation and preservation of the brams of man and of the higher mammals. This substance, commonly employed in a 4 per cent, solution (10 per cent, formalin) produces but slight alterations in form or in color and gives a good consistency to the tissues, although it causes a marked increase in weight and in volume. Table 1 shows the various solutions containing formaldehyde that were used as fixatives of the brain of the albino rat and their effects on the brain weight.
 +
 +
TABLE V
 +
 +
 +
 +
BAT
 +
 +
NO.
 +
 +
 +
 +
SOLUTIONS USED POR FIXATION
 +
 +
 +
 +
WSIQBT OP
 +
 +
BBAIN IN PERCCNT.
 +
 +
I ORAMS ON GAIN OR
 +
 +
, RSyOVAL LOSS IN
 +
 +
FROM FIXING WEIGHT
 +
 +
SOLUTION
 +
 +
 +
 +
I WEIGHT OF j I BRAIN IN GRAMS AFTER REMAINING I IN 70% ALCO-'
 +
 +
HOLPOR I 48 HOURS I
 +
 +
 +
 +
PER CENT. GAIN OR LOSS IN WEIGHT
 +
 +
 +
 +
♦1
 +
 +
2
 +
 +
4
 +
 +
3
 +
 +
5
 +
 +
♦27
 +
 +
18
 +
 +
37
 +
 +
♦38
 +
 +
41
 +
 +
46
 +
 +
49
 +
 +
50
 +
 +
♦32
 +
 +
33
 +
 +
10
 +
 +
 +
 +
I 4% Formaldehyde i 2
 +
 +
4% Formaldehyde 2
 +
 +
4% Formaldehyde | 2
 +
 +
Formol-Muller (cold) 2
 +
 +
Formol-Mtiller (warm)
 +
 +
Alcohol-f ormol
 +
 +
Zenker-formol
 +
 +
Marina's fluid
 +
 +
Marina's fluid
 +
 +
Sublimate-f ormol
 +
 +
Sublimate-f ormol
 +
 +
Sublimate-f ormol-acetic
 +
 +
Sublimate-f ormol-acetic
 +
 +
Graf's fluid (5% formalin)
 +
 +
Graf's fluid (10 % formalin) . Bouin'spicro-f ormol
 +
 +
 +
 +
5750
 +
 +
.8200
 +
 +
6778
 +
 +
.2437
 +
 +
1880
 +
 +
.6392
 +
 +
.6040
 +
 +
2219
 +
 +
2146
 +
 +
3315
 +
 +
0512
 +
 +
7687
 +
 +
8944
 +
 +
.1520
 +
 +
9283
 +
 +
7881
 +
 +
 +
 +
+33
 +
 +
+54 +50 +21 +22 -10
 +
 +
- 2 -33 -35 +21 + 17
 +
 +
- 2 + 8 +23 + 7 -00
 +
 +
 +
 +
1.5706 1.6436 1.6577 1.5537 1.8711 1.5147 1.3297 1.2913 1.2546 1.6565 1.3687 1.5003 1.5221 1.7421 1.5994 1.4663
 +
 +
 +
 +
-19 -10
 +
 +
- 7 -16 + 4 -16 -18 -29 -33 -14 -22 -17 -13
 +
 +
-12 -18
 +
 +
 +
 +
In this and in other tables, the percentages given are based on the computed
 +
fresh weight of the brain which is shown in table 6.
 +
 +
 +
EFFECTS OF FIXATIVES ON RATS' BRAINS 217
 +
 +
The brains of three rats (nos. 1,2,4) were fixed for forty-eight hours in a 4 per cent, aqueous solution of formaldehyde which had been made neutral with bicarbonate of soda as, according to Bayon ('05), a formaldehyde solution that has an acid reaction is not suitable for histological purposes. In all three cases there was a large initial gain in the weight of the brain which was followed by such a loss in weight after the brain had been brought into 70 per cent, alcohol that at the second weighing each brain weighed somewhat less than its computed fresh weight. The alteration produced in the brain weight of rats by aqueous formaldehyde solutions Are similar to those which this fluid causes in the brains of man and of sheep, according to the investigations of Parker and Floyd ('95), of Flatau ('97), and of Hrdlicka('06).
 +
 +
On making a histological examination of the brains that were fixed in a 4 per cent, solution of formaldehyde, it was found that this substance does not have as injurious an effect on the structure of the cells as do other fixatives that produce much less alteration in the brain weight. One of the large cells from the cerebral cortex of the half of the brain of rat no. 1 which was imbedded in celloidin is shown in fig. 1 . There is no apparent shrinkage of the cell body and the cytoplasm stains evenly and appears uniformly distributed. The nucleus, however, has suffered considerably from the action of the fixative, as it is decidedly larger than normal and its reticuluim is poorly preserved and stains very faintly.
 +
 +
A cell from the portion of the brain of rat no. 1 which was imbedded in paraffine after being cleared in chloroform is shown in fig. 2. This cell plainly shows the injurious effects produced by this mode of imbedding. The cell body is considerably shrunken, while the nucleus is slightly contracted and very irregular in outline. The smaller cells of the cerebral cortex do not seem to be as adversly affected by the paraffine imbedding as do the larger cells, and most of them appear fully as well preserved as do similar cells in brains that have been imbedded in celloidin or in celloidin-paraffine.
 +
 +
Many investigators have stated that for histological purposes formaldehyde gives the best results when used in combination with other fixing reagents. Of the various formaldehyde mix
 +
 +
218 HELEN DEAN KING
 +
 +
tures that have been devised, the Formol-Muller solution of Orth ('92) has been most highly recommended by Juliusburger ('97), and others as an excellent fixative for the central nervous system. The brain of one rat (no. 3) was fixed for twenty hours in FormolMuller solution, which was kept at room temperature (20° C); the brain of another rat (no. 5) remained for three hours in this solution heated to about 35° C. As shown in table 1, each brain had gained about 21 per cent, in weight when it was removed from the solution ; the subsequent loss in weight was, however, about 20 per cent, greater in the case of the brain which had been fixed in the cold solution than in that which had been fixed in the warm solution. When these brains were examined histologically the fixation of the cell structures was found to be no better in the one case than in the other. In both brains the large cells of the cerebral cortex appeared very similar to those in brains that had been fixed in 4 per cent, formaldehyde, as there was a slight swelUng of the nucleus and a poor fixation of the nuclear contents. As a cell fixative for the brain of the rat, therefore, this fluid seems to have no advantage over the simple aqueous formaldehyde solution.
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Parker and Floyd ('95) recommend a solution composed of 6 volumes of 95 per cent, alcohol and 4 volumes of a 2 per cent, solution of formalin as an excellent preservative for the brains of higher mammals. This solution was used as a fixative of the brain of ratno. 27. As the brain had decreased 10 per cent, in weight when removed from the fixing solution (table 1), it is evident that the addition of alcohol to formaldehyde prevents the swelling which is a characteristic action of aqueous formaldehyde solutions on brain tissue. As a cell fixative this fluid does not give satisfactory results. Although there is but little shrinkage of the cell body, the cytoplasm is invariably vacuolated in the vicinity of the nucleus, as shown in fig. 3, while the nucleus itself is somewhat irregular in outline and its contents are vaguely defined and stain faintly.
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Zenker-formol was used as a fixative of the brain of rat no. 18. The brain lost but 2 per cent, in weight as a direct result of the fixation; the later shrinkage, after the brain had been brought
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EFFECTS OF FIXATIVES ON RATS' BRAINS 219
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into 70 per cent, alcohol, being 18 per cent. The most marked histological effect of this fluid is on the cell nuclei. These structures always appear shrunken and irregular in outline, while their contents are very poorly preserved. Large cells of the cerebral cortex of the brain that was fixed by this method appear much as does the cell shown in fig. 2.
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Marina ('97) recommends as a fixative for the central nervous system a solution made as follows :
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Alcohol (96 percent) 100 ccm.
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Formol 5 ccm.
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Chromic acid 10 cgm.
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When used on the brain of the rat (nos. 37 and 38) this fluid produces marked alteration in the brain wieght and also in the cell structures. There is an initial loss of from 33 per cent, to 35 per cent, in the brain weight which is not materially altered by subsequent treatment of the brain with 70 per cent, alcohol. One of the cells from the cortex of the brain of rat no. 38 is shown in fig. 4. There is little apparent shrinkage of the cell body as a whole: the cytoplasm appears uniform, but it stains much more intensely than does the cytoplasm of cells in brains fixed with other formaldehyde solutions. On the cell nuclei this fluid had a very peculiar action. In the great majority of cases the nucleus appears swollen, and it has a very irregular outline with many indentations, as if the fixation had set up an unusual chemical reaction between the fluid contents of the nucleus and those of the cytoplasm. In some cases the nuclear reticulum seems to be entirely broken up so that the nuclear contents, save for the nucleolus, appears to be composed of small, rounded, deeply staining granules; in other cases, as shown in fig. 4, there are a few irregular clumps of nuclear substance scattered among the granules. Marina's fluid produced a much greater distortion of the nuclear structure in the cells of the cerebral cortex than resulted from the fixation with any of the other solutions that were used during the course of these experiments.
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Ewing ('98) states that a saturated solution of corrosive sublimate in a 5 per cent, solution of formalin gives a superior fixation
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220 HELEN DEAN KING
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of ganglion cells, bringing out the so-called chromatic network with great clearness. The brains of two rats (nos. 41 and 46) were fixed with i^iis fluid. Each brain gained considerably in weight as a direct result of the fixation, the greater gain (21 per cent.) being made by the brain of rat no. 41 which had remained the shorter time (four hours) in the solution. Both brains later lost considerably in weight, the loss being greater in the brain (rat no. 46) which had remained for twenty hours in the solution. This fli^d gives a very much better preservation of the cell structitres than might, perhaps, be expected from its effects on the brain weight. Very few of the large cells in the cerebral cortex show any evidence of shrinkage, and the cytoplasm always appears uniform. The nuclear reticulum is fairly well preserved and it stains deeply; but the nucleus itself is usually slightly enlarged. The large cells in the cerebral cortex of the brains fixed by this solution appear very much like that shown in fig. 13.
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One of the solutions recommended by Cox (^98) as a fixative for the spinal ganglioxi cells of the rabbit is made as follows:
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Corrosive sublimate (saturated aq. solution) . . .30 parts
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Formalin 10 parts
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Glacial acetic acid 5 parts
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Comparatively slight alterations are- produced in the brain weight as a direct result of fixation in this solution (table 1: rats nos. 49 and 50), although after subsequent treatment with 70 per cent, alcohol the brain loses from 13 to 17 per cent, of its computed fresh weight, depending on the length of time it has remained in the solution. As a cell fixative for the brain of the rat this fluid cannot be recommended. In all cases the nuclei of the large cells in the cerebral cortex are swollen, and the nuclear reticulum appears much like that shown in fig. 1.
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The picro-formol solu!tion of Graf ('97) certainly suffers from the omission of acetic acid, as Lee ('05: p. 77) has stated. This solution, made with 5 per cent, formalin, was used as a fixative of the brain of rat no. 32. The brain gained 23 per cent, in weight as a direct result of the fixation; but after remaining in 70 per cent alcohol for forty-eight hours it weighed practically its corn
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EFFECTS OF FIXATIVES ON RATS' BRAINS 221
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puted fresh weight. A cell from the cortex of this brain is shown in fig. 5. The cell outline is regular and the cytoplasm appears uniform; the nucleus, however, is swollen and there is a very poor preservation of the nuclear contents.
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The brain of rat no. 33 was fixed in Graf's fluid made with 10 per cent. formaUn. This fluid produces a very different effect on the brain weight from that which results from fixation with Graf's solution whichcontainsasmalleramountofformalin (table 1 :ratno.32). The initial increase in the brain weight is but 7 per cent., and the subsequent loss in weight, aftet the brain has been treated with 70 per cent, alcohol, is sufficiently large to make the final weight of the brain 12 per cent, less than the computed fresh weight. The stronger solution does not give as good a preservation of the cell structures in the cerebral ccfrtfex as does the solution that contains the 5 per cent, formalin, as there is a distinct shrinkage of the cell body in addition to an alteration of nuclear structure similar to that shown in fig. 5.
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The picro-formol solution of Bouin C97), which was used to fix the brain of rat no. 10, gave a much better preservation of the nerve cells in the cortex than did artSy of the other formaldehyde solutions that were tried, and it produced practically no alteration in the brain weight. The brain was imbedded in celloidinparaffine and sections of it show an admirable preservation both of cell and of nuclear structure. A careful comparison between the cerebral cells in this brain and those in brains fixed in the solution of Ohlmacher ('97) shows that the latter solution gives a slightly better fixation of the nuclei than is obtained with Bouin 's fluid. No further experiments were therefore made with Bouin's fluid which is doubtless as excellent a fixative for the central nervous system as it seems to be for many other kinds of materials.
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Judging from the results obtained on the brain of the rat, solutions containing formaldehyde give, in general, a good fixation of the cell body, but they tend to produce a swelling of the nucleus which is usually accompanied by a poor preservation of the nuclear contents.
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Before the introduction of formaldehyde as a fixing and hardening reagexit, bichromate of potassium (K2Cr207), either in simple
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222
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HELEN DEAN KING
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aqueous solution or in combination with sodium sulphate as Miiller's fluid/' was very generally emjHoyed for the fixation of manunalian brains. Donaldson ('94) studied the action of this preservative on the weight and volume of the brains of sheep. He found that, in general, the weight of a brain increases according to the number of days it is left in the solution; the gain being about 17 per cent, as a result of one day's action of a 2| per cent, solution, increasing to a maximum of 38 per cent, after an immersion of two years in the fluid.
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TABLE 2
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RAT NO.
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