Meckel1812-1 Anatomy 2-9

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Meckel JF. Handbook of Pathological Anatomy (Handbuch der pathologischen Anatomie) Vol. 1. (1812) Leipzig.

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Handbook of Pathological Anatomy Volume I (1812)

Section IX. - Of the Serous System

General Remarks On The Serous System

A. Its Normal State.

§ 353. The serous system is very well marked both in form and texture, although in more than one respect it seems to be but a slight modification of the cellular tissue. It is not a connected system, but it exists in all parts of the frame and assists in uniting different organs. We may refer to it the synovial membranes^ or the articular capsules, which in structure and functions do not differ from it, and hence divide it into the proper serous system and the synovial system.

(1) Bedard does not admit this change into fat, and thinks that the error arises

from simple appearances, and that the muscular fibres are only discolored. This opinion is contradicted by well established facts. F. T.

(2) Gay Lussac in the Annales de chimie et de physique, vol. iv., p. 71.

(3) Tiedemann relates a case of accidental bony concretions which were very abundant in several muscles of a man affected with gout, {Deutsches Archiv für die Physiologie, vol. v., p. 355.) These concretions were attended with the ossification of several arteries. They were composed of the phosphate and a small portion of the carbonate of lime, and of one fifth of animal matter, without any appearance of proper organization. F. T.

(4) Fleischmann, Leichenoeffnungen, 1815, p. 112.

(5) Dumas, in Sédillot, Recueil périodique, vol. xxv., p. 74.

(6) Colomb, Å’uvres Chirurg., p. 72.

(7) Dumas, Méd. éclair., vol. ii.

(8) Bichat, Traité des membranes, Paris, an viii., p. 78-111 and 202-292.

§ 354. This system always assumes the membranous form. It is composed of a certain number of round sacs, which are entirely distinct from each other, and are usually perfectly closed.

The form of these sacs is not every where the same. They may be divided, in this respect, into two large sections. The first comprehends the simple sacs, which present in all parts a rounded surface. The serous membranes, which in part compose this section belong to the synovial system ; they are always placed between the tendons and the bones, and are badly termed the biirsÅ“ mucosÅ“. These bursæ cover only one part of the tendon under which they are found. The serous membranes of the second division are more complex in their forms, and seem composed of two sacs, one of which is found within the other. It appears like a simple sac, folded on itself in a portion of its circumference, or strengthened in part in its proper cavity by the action of a foreign body ; if this body be removed, or, what may be done in some places, if the turned portion of the serous membrane be detached and the latter be thus insulated, we obtain a single round sac. In the normal state, the external and the internal sacs do not communicate nor touch, except where the sac seems to be reflected on itself. Further, the external sac always forms a much larger cavity than the internal, although, in several serous membranes, the latter is more capacious than the former, because the membrane has so many folds. The following are all the proper serous membranes, which are found in the normal state, viz. the tunica arachnoidea, the pericardium^ the pleura, the peritoneum, the tunica vaginalis testis, the synovial membranes, and several hursæ mucosÅ“. All these membranes form perfectly closed sacs ; the part turned in always incloses an organ to which it adheres intimately ; in the serous membranes this organ is generally a viscus ; the synovial capsules generally inclose the extremities of two adjacent bones which move upon each other ; and finally, the bursæ mucosæ which belong to this section contain a part of a tendon. The adhesion, which is slight where the membrane is reflected upon itself, becomes more and more intimate, and often increases so much that, as in the testicles, the spleen, the lungs, and all the articular extremities of the bones, it is impossible to separate the serous coat from the parts below, except to a slight extent ; while in all the other parts the inner sac is in fact- blended with them.

This adhesion is not equally intimate in every part. Thus, for instance, the peritoneum adheres but feebly to those parts of the bladder, of the duodenum and of the pancreas which are covered by it, rather more to the viscera of the digestive apparatus, and very firmly to the interna|^grgans of generation in the female. Generally the harder the parts fe which the serous membrane is connected, the more firm is its union. This proposition applies to the external portion of the serous membrane as well as to its reflected portion. The glands and muscles are separated from it with facility, but the fibrous organs and the cartilages with great difficulty.

§ 355. The serous membranes a,re reflected directly upon themselves, so that the internal sac is closely applied upon the organ it covers ; and between it and this organ there is a depression of variable length formed by two folds, between which the vessels and the nerves proceed to the organs contained in the sac. We may mention, as instances of the former arrangement, several portioirs of the large intestine, particularly the ascending and the descending colon, a part of the liver and the heart ; all the small intestine, and the spleen are examples of the second. In the former case a portion of the organ is most usually uncovered by the serous sac ; this is the case in the ascending and the descending colon, the upper and posterior portions of the liver. In the latter, but a small portion of the organ, the point where its vessels enter, is destitute of the serous membrane. These two arrangements are generally found in the same organ, as is the case with the peritoneum, where it covers the liver.

Besides these folds which exist between the external and the internal sac, and the organs covered by the latter, the serous membranes form others of a ditierent character. They always extend beyond the organ covered by the internal sac ; but then sometimes they hang loosely and are again reflected on themselves ; sometimes they pass from one of the parts contained in the common external sac to another. The former arrangement is seen in the epiploon, the second in the external envelop of the round ligament in the ilio-femoral articulation, in the similar bands contained in the knee-joint, and in the second class of the tendinous bursæ. However, when closely examined, all these processes are essentially the same, that is, they are all produced by the transition of the internal serous sac from one organ to another. In fact, the omenta differ from the tendinous bursæ only in being more extensive, so that they are obliged to fold upon themselves, when passing from one organ to another.

We however find in some places folds which are perfectly loose, and which arise from the surfaces of the organs lined by the internal sac ; such are the appendices epiploicæ of the large intestine, and the prolongations which in many capsules of the joints, for instance, those of the knee- and hip-joints, cover the glands of Havers.

§ 356. The folds and prolongations of the serous membranes are usually connected with the respective situation of these membranes, and of the organs which they cover. In fact, in certain circumstances they cover organs, which they do not cover when these circumstances vary. Thus, the intestines, when filled and distended, are imbedded in the mesentery, the stomach in the omentum, and the impregnated uterus in the broad ligaments.

The serous membranes differ, in fact, from the structure of the organs they cover, and they must be considered only as drawing a more exact line of distinction between these other organs, in respeçt either to situation alone, or to their mode of existence. Thus they envelop the most important organs : the brain, the spinal marrow, the lungs, the heart, the intestinal canal, and the principal parts of the genital apparatus.

Hence why their diseases have less effect upon the organs covered by them than those of other membranes. In dropsies, in thickening, and ossifications of the serous membranes, the subjacent organs are perfectly healthy, even when they adhere intimately, as in the testicle. Still, whenever the union is such that the membrane and the organ are one, as in the capsules of the joints, the diseases of the former soon affect the latter. For the same reason, a part of the the peritoneum not only abandons certain organs in the circumstances above mentioned, but leaves without inconvenience the parietes of the abdomen either abnormally, as in hernia, or naturally, as in the descent of the testicles into the scrotum. We must not forget however that, in the cases above examined, there is an alternate separation and reunion of the organs with the serous membranes, but also a distension and contraction of the same organs.

§ 357. The serous membranes, even those which have a complex form, are perfectly closed, although at first idew they seem to be perforated, yet they only fold upon themselves and are perfectly closed. There is but one exception to this rule, viz. the abdominal orifice of the fallopian tubes, which open into the peritoneal cavity on each side. This too is the only instance where a serous membrane is continuous with a membrane of a different class, which, in this case, is a mucous membrane ; for we cannot mention as such the communications w'hich exist between the different parts of a serous membrane, as the external arachnoid membrane and that which Unes the cerebral ventricles, between the great cavity of the peritoneum and that of the omenta, &c. This complete closure of the serous membranes explains why the congestions of serum never extend beyond the limits of their cavities in dropsy of the pericardium, of the pleura, of the peritoneum, and of the tunica vaginahs testis.

§ 358. The internal face of these sacs in the normal state is always smooth, the external is rough, and united to the adjacent parts by mucous tissue, at least most generally, although there are several exceptions ; for instance, both faces of the lower portion of the arachnoid membrane are loose. In fact, in the serous membranes of the second class, the external face of the mternal sac which looks toward the inner face of the external sac is smooth and loose, while the internal face is uneven and attached ; but this arrangement does not contradict the law we have established, since the internal sac is only a reflected portion of the external. The smoothness of all the organs which exist in serous membranes comes only from the internal sac ; when detached, they seem rough and covered with mucous tissue, and their surfaces are never smooth in those parts where, in the normal state, the serous membranes do not cover them ; such is the hver in several places, the post^or face of the ascending and descending colon, most of the posterior part of the rectum, a large portion of the uterus, of the bladder, &c.

These sacs are always thin in proportion to their other dimensions, but there is never a direct and constant relation between their thickness and their capacity. They are always more or less transparent, white, and shining, but less so than the fibrous organs with which they are intimately connected. Thus the arachnoid membrane lines' the internal face of the cerebral and of the spinal dura mater ; the pericardium is covered by a fibrous membrane, and when this is deficient it is supplied by the tendinous part of the diaphragm : the pleura is situated under the periosteum of the ribs and the tendons of the intercostal muscles ; the tunica vaginalis testis is placed under the tendon of the cremaster muscle ; the synovial membranes under the fibrous ligaments and upon the periosteum of the bones.

§ 359. The whole serous system appears to be but a slight modification of mucous tissue, but of a mucous tissue more dense than usual, and coagulated in larger layers. This is seen from the following considéra tipns ;

1st. From its external appearance. Both have the same color. If the mucous tissue be inflated with air, cells are produced which cannot be distinguished from the serous tissue, especially from its thin portion, as the peritoneal coat of the intestines, the epiploon, the arachnoid membrane, &c. So too the fibrous membranes may be converted into mucous tissue by maceration, and by inflating air into the subjacent cellular tissue.

2d. It is not unfrequent to find simply mucous tissue filled with synovial fluid in the place of certain parts of the synovial system.

3d. The serous membranes, like the mucous tissue, present a homogeneous mass ; we see no trace of fibres.

4th. Like the mucous tissue, they receive few blood-vessels, so that they are composed almost entirely of absorbent and exhalent vessels.(l) Mascagni thinks them formed only of absorbents, because mercury injected into the lymphatic system converts them into a tissue of these vessels ; but when the blood-vessels are injected, or when inflammation, attacking the serous membranes, fills the capillaries with blood, the serous system becomes a tissue of blood-vessels. In fact we find numerous and considerable blood-vessels ' oir the external surface of these membranes, but they do not enter into their composition. The arachnoid membrane is entirely destitute of vessels. The serous membranes when exposed in a living animal are colorless, and blood does not issue from them when they are divided after death.

5th. Like the mucous tissue they are destitute of nerves.

6th. The functions of the mucous tissue and of the serous membranes are the same, viz. exhalation and absorption. (2) Like the mucous tissue, the serous membranes form around the parts they envelop a perfect limit, and which is more marked in them on account of the great

(1) This is not the opinion of Rudolphi. He says that the serous membranes have no vessels, and that they may be easily detached from the organs which they c^ver, especially when there is a dropsical state. If we then examine them_ with a microscope there are no traces of vessels. They are formed only of cellular tissue, of which they constitute the bounds to free surfaces. Ribes has ascertained the same fact by numerous dissections. P- T (2) According to Rudolphi they do not secrete, but only allow the perspiration

furnished by the cellular tissue to pass through them, fulfilling in respect to A A'® same duty performed by the epidermis in regard to the perspiration of the skin. Nor does he admit that they are porous. P- P"

importance of these organs. As all the organs are imbedded in mucous tissue, which is the common organ of nutrition and formation, so the envelops of the fetus in structure and functions resemble serous membranes exactly. We may then call them the formative membranes, as the mucous tissue has received the term of formative or generative tissue*

§ 360. The serous membranes possess a great degree of extensibility and of contractility ; hence they remain uninjured even when greatly distended by dropsies or tumors. We must however remark, that, in such cases, they are not only distended, but their folds are partially developed, and are a little displaced from the looseness of the mucous tissue which unites them to the adjacent parts, and that they really increase in mass. Hence why, in dropsies for instance, instead of being thinner in proportion to the enlargement they have acquired, they are thicker. That the changes they experience result in great part from a forced extension is proved by the rapid and great diminution of their cavities, when the substances which distend it (for instance, the serum in dropsies) are removed ; and this diminution takes place without wrinkles or folds.

The serous membranes, properly so called, possess these properties in a greater degree than the synovial capsules. The latter are torn when a great forcé acts upon them, as in dislocations ; the former are distended, as in hernia. We must not forget, however, that this difference is mostly owing to the difference in the mode of connection with the subjacent parts.

In the healthy state the serous membranes are insensible, or sensible only in a slight degree ; but they become highly so in diseases, and when they are inflamed the pain is very acute.

§ 361. The functions of the serous membranes are, to insulate the organs they envelop, and to facilitate their motions, by rendering their surfaces smooth, and by exhaling a lubricating fluid, which, perhaps, in the normal state of the proper serous membranes, has the form of vapor, but is liquid in the synovial system. Both resemble strongly, in their essential properties, the serum of the blood ; that of the proper serous membranes differs but little from it ; that of the articular membranes, called synovia, is very analogous to it, but differs from it as we shall mention hereafter! Both contain a large proportion of water, a little albumen, a gelatinous substance, and several salts.(l)

§ 362. The serous membranes themselves differ in respect to their external form and their texture, but more in regard to the former than the latter.

Another point of resemblance between these tissues is the similarity of the diseases which affect them. On this point Prof. Horner remarks, ( Treatise on Gen. and Spec. Anat., vol. ii. p. 7,) “ My own experience goes to prove that dropsy seldom manifests itself to any extent in the cellular tissue without also going to the serous texture and the reverse.

(1) Hewson, On theproperties of the lymph contained in the different cavities of the body, in Exper. inq., ii. ch. vii.— Bostock, in Nicholson, Journal, vol. xiv. p. 147.

Have they originally the form of closed sacs ? This is probably not the case with all. We have every reason to think that the pericardium and the peritoneum are at first open, for, in the early periods of existence, the heart and the viscera of the abdomen are uncovered, although it afterwards happens that the latter, exposed as before, are still covered by a prolongation of the peritoneum which accompanies them.

The form of the serous membranes varies at different periods of life ; they disappear in some parts, and are developed in others ; these differences de[)end on the changes which supervene in the situation of the organs within their cavities. Thus the fold of the peritoneum which at first traverses the umbilical ring disappears in time, while another forms and engages itself in the inguinal ring, when the testicle begins to descend from the abdomen into the scrotum. Even the number of the serous membranes, considered as so many distinct sacs,, varies at different periods of life. Thus the tunica vaginalis testis is at first a continuation of the peritoneum, but sometime after birth the upper part is obliterated, aird two separate cavities are formed, the peritoneal and the vaginal.

The tissue of the serotrs membranes is more uniform ; except that, like all the organs, they are at first more loosely attached to the adjacent parts, whence they are more easily insulated in the early periods of life. This arrangement is not always applicable, except to their external fold : it does not, extend, at least in all cases, to their internal and reflected layer. Thus we cannot detach the gerous membranes from the tunica albuginea and from the articular capsules with greater facility in the fetus than in the adult.

The characters of the fluid they exhale -probably vary as do those of all others in the course of life, that is, it is thinner and more watery in youth than in advanced age. This conclusion is drawn from comparing the results of analyses made by Rostock and Hewson. The latter states the fluid to be albuminous and gelatinous, the former that it resembles fibrin.

B. OF THE SEROUS SYSTEM IN THE ABNORMAL STATE.

§ 363. The serous membranes present remarkable anomalies in form and in texture. The primitive deviations of formation are somewhat rare. They consist usually in the suspension of development — such as, 1st, the absence of a portion of these membranes, especially the pericardium, the pleura, and the peritoneum, when the heart, the viscera of the thorax and abdomen are exposed ; 2d, the abnormal communication between different serous membranes, the cavities of which are not properly united, except during the earliest periods of life. To this we refer particularly the communication existing between the tunica vaginalis and the peritoneum, when the canal between them is not effaced, and which is occasionally the cause of congenital inguinal hernia.

But other primitive deviations of formation also occur. As, for instance, the existence of a serous sac within the proper sac, communicating with it by a more or less narrow opening, and inclosing a portion of viscus which is generally at hberty and which separates it from the rest. This phenomenon has been observed only in the peritoneum, and it is curious, as being essentially the abnormal repetition of a normal formation.

The serous membranes are liable to accidental deviations of formation, as they take part in hernia. Here a portion of serous membrane generally detaches itself from the parietes of the cavity to which it adheres, passes across a separation which is naturally broad, or is enlarged by the action of an external cause, and thus forms a sac called the hernial sac, {saccus hernia, ) into which penetrate some of the viscera lodged in its cavity and covered by its membrane. This latter is rarely torn, and the viscera seldom protrude unless preceded by it, and it is unfrequent for the hernia to have no sac ; this case happens only after great violence, and even then the hernia occurs only in certain places, for instance in the upper wall of the peritoneum. The hernial sac also is rarely ruptured or opened by the effects of previous ebsease, so as to permit the viscera inclosed by it to be in immediate contact w'ith the common integuments. The peritoneum only is subject to these different accidents, because, of all the serous membranes, it adheres the least to the parietes of its cavity, and also because the parietes of the abdomen are less protected by the bones than those of the other two splanchnic cavities, and cannot resist the efforts of external agents so powerfully.

The serous membranes are not unfrequently distended extremely by the fluid they exhale. This fluid often accumulates in very great quantity, and constitutes the different kinds of dropsy {hydrops.) Here, the animal substance is thin,and generally less abundant,so that the fluid of dropsy may be regarded as the serum of the blood, which has lost from two thirds to four fifths of its albumen ; however, the proportion of this substance is sometimes very much increased, doubtless, on account of the absorption of the watery portion.(l)

§ 364. The other changes in the forms of the serous membranes are, the results of morbid affections, and especially of inflammation, which often affects them. (2) Inflammation of the serous membranes tends to terminate by effusion into their substance which results in a thickening, or by effusion on their surfaces, which causes a mutual adhesion of the corresponding faces of the external and internal sacs, al (1) Schreg-er, Fhndorum corporis animalis chemicÅ“ nosologies specimen, Erlangen, ISOn, p. 16-24. — Marcet, A chemical acconnt of various dropsical fluids ; in the Edinb. med. and surg. trans. — Berzelius, On animal fluids ; Med. chir. trans., vol. ii., p. 251-253. — Bostock, On the nature and analysis of animal fluids, ibid., vol. iv., p. 52.

(2) Rudolph! maintains that inflammation is not situated in these membranes,

but in the organs they cover ; that they cannot inflame any more than the epidermis ; and that pleuritis, pericarditis, and peritonitis are inflammations of the surface of the lun^s, heart, and abdominal viscera, &c. Chaussier and Rihes entertain similar opinions. If serous inflammations he, in fact, only inflammation of the subvisceral mucous tissue, we can conceive of the rapidity, the intensity, and the danger of these inflammations, and the abundant products they furnish. F. T.

though the membrane is not destroyed by suppuration. These adhesions vary much in extent, solidity, structure, and number. Sometimes they cover the whole surface of the serous membrane and the parts it envelops, so that it becomes almost impossible to distinguish the latter from each other, and one is induced to believe there is no external sac; sometirnes they are confined to one or a few points of the external and internal sacs, whence only the organs situated in those places adhere. They may, too, become very intimate, even to a degree that where the united parts seem to make only one, or very loose and easily broken. Finally, the adhesions are sometimes very short, and sometimes long ; in the latter case they form cords, ligaments, and membranes, termed generally false membranes {psetido-membranÅ“), which in nature more or less resemble that- of the serous membranes, and which are often attended with fatal results, particularly when they are developed in very movable points or parts which may ghde into the rings they produce, as in the intestines.(l )

Farther, these adhesions probably take place only after inflammation, and are never primitive, although Bichat admits the contrary in regard to some perfectly organized ligaments, often found between the external and the internal sac of the pleura, and which are evidently composed of two folds fitted to each other, and although Tioch(2) maintains this opinion, in regard to some analogous ligaments situated between the heart and the pericardium, because they resemble those presented by the hearts of several reptiles in their normal state. . It is certain, at least, that the most perfect organization of these appendages is not sufficient to justify this opinion, because, parts which have a more perfect organization, as bones, teeth, and even whole serous membranes, are often developed by a vital act, which does not differ essentially from inflammation.

We do not observe the same form in all the alterations in texture of the sero' s membranes which result from inflammation, and are characterized by the thickening of their substance. Thus, in the internal sac of the pericardium, broad smooth layers appear, which are termed macula, cordis, and in the peritoneum numerous small, hard, round elevations very analogous with the miliary eruption.

§ 365. The serous system tends much to ossify, and in this relatio'U presents the same differences as in that of adhesion. Sometimes, in fact, the substance of the membrane ossifies; sometimes smooth an! usually round bodies, varying in number and size, form on its surface, these are more or less loose, and are often entirely detache 1 from the membrane and float freely in its cavity. These phenomena are common to all the serous membranes, although found in some more frequently than in others. Thus, that portion of the peritoneum which covers the spleen, is, of all others, the most disposed to ossify ; next comes the internal sac of the tunica vaginalis testis ; the others, except the tunica arachnoidea which rarely ossifies, ditfer little from each other in this respect.

(1) Villcrmé, Vrailé des J'ausscs membranes. Paris, 1814.

(2) Mem. de Montpellier, vol. ii, p. 351.

These accidental ossifications almost always have the form of broad layers, and often become, especially in the spleen, very large, so that even the proper substance is frequently entirely concealed. The synovial membranes ossify less frequently ; still, however, as their internal sac identifies itself with the articular cartilages, we may say that they become cartilaginous even in their normal state, and that ossification of the proper serous membrane is only an abnormal repetition of the normal state of the synovial membrane.

It is not uncommon to see developed in the substance of the synovial membranes different osseous concretions, which are often found in considerable number in these organs, and more frequently in the bursæ inucosæ. These concretions do not,- however, belong to them exclusively, for they occur also in the proper serous membranes, particularly in the tunica vaginalis testis, and sometimes, although less frequently, in the peritoneum, in the pleura, and in those parts of the arachnoid membrane, which are blended with the dura mater.

Most usually, and even almost always, these loose osseous concretions arise as we have stated. Sometimes they may be loose primitively, and be developed in the blood, or in another fluid effused into the articulatioir by some external injury, but even then, we have reason to think that a connection between the effused blood and the synovial membrane was established before the bone was developed. The formation of these concretions in the serous membranes, which are not in relation with the bones, proves, at least, that the adjacent extremities of the latter have no influence, as Hunter thought, on the change of the effused fluid into osseous substance.

Besides these anomalies, which are somewhat frequent, there are others more rare ; such as the development of loose, soft processes, several lines long on the internal face of the synovial capsule of the knee-joint, of which we have a specimen before us ; perhaps, however, it is only the first stage leading to the formation of the osseous concretions which we have already mentioned.

§ 366. The serous tissue is one of those which has the greatest tendency to abnormal repetition in the body. The accidental serous membranes are often the foundations of other abnormal formations, since they are developed before them, and give rise to them. They have been called cysts (cystic), and encysted tumors (tumores cystici), and have all the essential characters of serous membranes. They constantly form perfectly closed sacs, smooth internally and rough externally. They are produced by mucous tissue, have but few bloodvessels, and fulfill the same functions as the proper serous membranes, although the substances within them are not always of the- same nature as the serous fluid, and are not always liquid.

Probably these cysts are not developed, as is generally thought, mechanically, by an effusion compressing the cellular tissue returning again on itself, and thus changing into membrane. Bichat has already conteBte J this theory, by stating that the cysts are most analogous to the serous membranes ; that the secretion continues to take place within them, while compression would probably make them impervious : that the cellular tissue does not diminish around them, and that we must suppose from the hypothesis admitted, that the secreted fluid exists before the secretory organ. He thinks these organs are formed, like all others, in the mucous tissue, and that exhalation does not commence within them until their structure is completely developed. However, it cannot be denied, that the formation of the cyst has not been preceded by the effusion of a fluid into the mucous tissue ; the cyst, however, does not develop itself, because this fluid compresses the surrounding mucous tissue, but it is formed at its own expense ; because it has the power of organizing itself This theory appears very probable on account of the analogy of structure and formation existing between the mucous tissue and the serous membranes, and because of the pathological phenomena by which the cysts are developed. In fact, we not unusually find either in the cavities of the normal serous membranes, or in the accidental cysts, an immense number of small loose cysts which have no trace of former adhesion, and which are filled with a serous fluid, which is generally limpid. These small cysts called hydatids{\) {hydalides), are usually surrounded with an analogous liquid. They are evidently formed only at the expense of the fluid effused in the cavity of the serous membrane, by its separation into a solid and a fluid portion. According as this fluid is effused into the mucous tissue, or into a serous membrane, the cysts which arise from it, unite to the adjacent parts by the surrounding cellular tissue, and receive blood-vessels or remain loose and without any adhesion. The serous membranes tend more than any other organ to produce these different kinds of cysts, and even when they seem to be developed in the substance of the viscera, as, for instance in the liver, which is sometimes entirely destroyed, their developmeilt probably commences by the portion of peritoneum which covers them, for we always find them on its surface, and on some part of their circumference.

(1) These cysts have been termed acephalocysts by Laënnec, who considers them as animals, an opinion which Cuvier and Rudolphi do not adopt. These naturalists and their followers assert, that the acephalocysts exhibit no appearance of vitality ; but even when it is g'ranted that they do not enjoy an existence independent of that of the livina" bodies in which they occur, they are not the less irritable, like all living' parts, and we cannot conceive them otherwise. Besides we have no doubt but these vesicular productions are produced by inflammation. Veit long ago proposed this theory, (Einige Anmerkungen über die Entstehung der Hydaiden, in Archiv für

die Physiologie, vol. ii., 1797, p. 436,) which G. Jager has since developed. (Beobachtungen über Hültenwürmer im Menschen und einigen Säugihieren ; in Meckel, Deutsches Archiv für die Physiologie, vol. vi., p. 495.) He has thus given an experimental base of the doctrine of the spontaneous generation of intestinal worms, which Rudolphi and Bremser,assuming reasoning and analogy as guides,have adopted as the only one which harmonizes with the present state of our knowledge of animal physiology and general physics. In fact, the acephalocysts lead insensibly to the proper entozaries by the echinococci, which naturalists no longer recognize as intestinal wonns, notwithstanding the special organs with which they are provided, and which difier but slightly from the cÅ“nurus, which all herminthologists object to place in their catalogue. F. T,

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Reference

Meckel JF. Handbook of Pathological Anatomy (Handbuch der pathologischen Anatomie) Vol. 1. (1812) Leipzig.

Volume 1. Table of Contents

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Cite this page: Hill, M.A. (2024, April 19) Embryology Meckel1812-1 Anatomy 2-9. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Meckel1812-1_Anatomy_2-9

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