Paper - On the origin and phylogenetic significance of the female genital passages

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Wichmann SE. On the origin and phylogenetic significance of the female genital passages. (1914) J Obstet. and Gynaecol. 190 - 206.

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This historic 1914 paper by Wichmann describes female genital tract development. Note that the early description of embryonic origin has been recently corrected as paramesonephric (Mullerian) duct origin on the basis of molecular studies.


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On the Origin and Phylogenetic significance of the Female Genital Passages

By S. E. Wichmann, M.D.,

First Assistant at the Lying-in Hospital of Helsingfors University.

After a paper read before a meeting of the Society of Finnish Physicians and Surgeons, May 12, I914.

Introduction

The extraordinary amount of research which, at the beginning of the 19th century, was devoted to the then almost virgin fields of comparative anatomy and of evolutionary doctrine, touched likewise to a great extent upon the development of the male and female genital passages with a view to explaining the relation of their various parts to eventually corresponding parts in the opposite sex. In the works of the earlier anatomists, such as De Graaf, Santorinus, Morgagni, etc., some attention is already paid both to the normal and pathological formations observed by them, and more especially to the female generative organs.


The greater the number of new observations which the steadily perfected modus operandi offered for discussion, the more numerous were the new questions which arose, and so much more difficult was it often the case to keep the new observations in harmony and in a theoretical whole with the earlier admitted truths.


Hence one can easily perceive the difficulty, nay, almost the impossibility, for these anatomists to find directly the right tract, as in the female generative organs they had to work up a system where the urinary and generative organs have in many different ways been connected with each other. During the phylogenetic as well as during the ontogenetic periods of development they have undergone such complicated alterations in shape, position and function that the normal development of these systems to this very day, in spite of arduous research work, has not been fully explained.


Anatomists’ attention and interest were increased, especially regarding the development of the urogenital apparatus, since the great physiologist and anatomist, Johannes Müller,1 showed in 1830 that the female genital passages (tubes, uterus and vagina) and the male passages (epididymis and vas deferens) were not homologous formations, but that the former in early phases of the embryo appear independently on the lateral part of the mesonephros devoid of any visible communication with the mesonephros tubules and the future male passages.


Until the "sixties it was imagined that the female genital passages (known during the embryonal stages as the l\/[üllerian ducts) first made their appearance in younger embryos as solid cell strings on the lateral part of the mesonephros ridges and comparatively later obtained a lumen which at last, through what the older anatomists with predilection described as “ dehiscens,”


was put into open communication with the peritoneal cavity at the cranial end of the duct (cf. J. F. Meckel,2 I820; Kobelt,3 1847, etc.). A young anatomist. Bornhaupt,4 through help offered by the gradually improved working methods discovered in 1867, found that the Müllerian duct in young hen embryos first appears as a funnel-shaped invagination at the lateral surface of the cranial part of the mesonephros ridge, and that this invagination is formed of a “locally thickened peritoneal layer.” According to his observations, this invagination then grew out in a distal direction into a duct rapidly extending along the newly formed Wolffian duct through the mesenchyme tissue to the cloaca. Some years later the celebrated Berlin anatomist, Waldeyer,5 was able to verify Bornhaupt’s observations, and henceforth the process of development of the Müllerian ducts has, in outline, become known and admitted.


At the same time Waldeyer in his best-known work, “ Eierstock und Ei,” applied a new term to Bornhaupt’s “ thickened peritoneal 1ayer.” He «called it “ Keimepithel,” or “epithelium germinativum, and traced both the reproductive gland or ovary as well as the genital passage or i\/hillerian duct from it. From examinations, of which space does not permit a detailed account, he quite rightly derived the male conducting passages from the tubules of the mesonephros. Moreover, he hinted that the epithelial cords of the male reproductive gland originate through proliferation of the mesonephros tubules towards the germ epithelium, which likewise appears in the male organism. Thus, according to Waldeyer, the “ Keimepithel ” was, de facto, a germ epithelium for female embryos only and not for male ones. Again, the sex cells and the conducting passages in the two sexes were not homologous formations; the male ones originating from the urinary system; the female, on the other hand, found their origin in the germ epithelium.


Waldeyer’s mistake was partly set right by two renowned embryologists, Janosik 5 and von Mihalkovics7 (1885), who at the same time from important researches clearly showed the homology between the glandular parts of the male and female reproductive glands.


  • Concerning the conducting passages they were contented, ‘as all later investigators, to admit the process of development earlier discovered by Bornhaupt and Waldeyer. As for the female genital passages, science has not yet arrived at any universally admitted facts regarding the evolutionary significance of the Müllerian ducts. Moreover, evolutionary "history has been at a loss to discover from what organs or from what parts of organs appearing in lower vertebrata this duct can be said to come.


Nevertheless, it is impossible to lay too much, emphasis on the extraordinary importance of settling the question above raised, since to know exactly the relation which exists. between the Müllerian genital epithelium, the germ epithelium and the surrounding peritoneal layer would give the key to the solution of several other so far unsolved problems. Thus we remain in total ignorance of the genesis of many anomalous and pathological formations lying in the vicinity of the female adnexa—for example, the hydatids, the serous cysts alleged on the peritoneal serosa, etc. Nor is the genesis of the so—called “ parovarian cysts ” out of discussion, and even quite recently some ovarian cysts have been said to be derived from the epithelium of the rete ovarü 3 and from the epithelium of the Müllerian duct.


During half a decade, and partly in connection with these problems, I have striven to collect the greatest possible amount of human material -comprising all embryonal and postfoetal ages, and have at length succeeded in gathering together an exhaustive series of cases. Besides this, during a stay at Bonn some two years ago, I had at my disposal Professor R. Bonnet’s well-known preparations of mammals, which offered an excellent opportunity of studying more closely the origin of the urogenital connection in mammals and incidentally the genesis of the Müllerian duct. Having during the study of all this material come to conclusions, which mostly differ from earlier expressed opinions, I beg to give a short account of results obtained as far as the question of the origin of the female genital passages, the genesis of the “ appendicular formations” in general and the hydatids in particular are concerned.


The practical work was carried out partly at the Histological Institutions at Helsingfors and Bonn, partly at the laboratories of the Pathological Institution and Lying—in Hospital of Helsingfors.


The questions discussed here and detailed accounts of the material studied have been partly published elsewhere (cf. “ Uber die Entstehung der Urogenitalverbindung und die Bedeutung der Müllerschen Genitalgange bei den Saugetieren,” Anatomische Hefte, Bd. 45, 1912, and “ Le developpement des appendices du ligament large et leurs rapports avec l’évolution phylogénétiques des canaux de Muller,” Archives de Biologie, T. 29, 1914).


Before however giving an account of my views relating to the genesis of the female genital passages I must review the results of those researches by means of which I tried some three years ago to solve the genesis of the urogenital connection. Both these questions have a very intimate bearing on each other, as will later appear from the following. Some words will likewise touch upon the phylogenesis of the urinar and genital systems from the earliest developing phases in the ertebrata.


Following the phylogenetic development of the urogenital apparatus in the Vertebrata a very close relationship between the urinary and genital systems is observed. Some scientists think that the ducts of the pronephros and the genital ducts of the Annelides are both derived from one and the same organs found in the ancestors of the Vertebrata. They also assume that these genital or pronephros ducts and the cells of the reproductive glands in these ancestors existed throughout the whole length of the trunk, and that the separate parts of the genital gland of the segmented body cavity communicated through these genital or pronephros ducts isolatedly with the surface of the body and used these ducts as conducting passages. Through the formation of a united body cavity in the higher Vertebrata the necessity of the segmentation of the genital gland and conducting passages disappeared, and thus the possibility of the formation of a continuous genital gland and an uninterrupted condu-cting passage was produced. This happened through a fusion of the segmented genital glands and an anastomosis formation of the separate excretory ducts.


As both these systems at the beginning of the evolution of the Vertebrata evidently existed throughout the whole length of the trunk, in order to imagine the primitive condition of the urogenital apparatus of the earliest vertebrate forms I drew up a diagrammatic outline, in reference to those used by Felix,9 of the formation of the pronephros segment (fig 1). Along the whole of the posterior and lateral wall of the body cavity a row of nephrostomes is depicted. In their vicinity, and especially in a medial direction between them and the mesenteric insertion, some genital cells are spread. The nephrostomes, the nephrostomal ducts,* the Malpighian corpuscles, the tubulus principalis and the conducting passage (primarer Harnleiter) mediate the connection between the body cavity and its surface. Besides this the more independent outer glomerulus is shown in red.


According to commonly admitted evolutionary principles we may assume that this primitive condition of the two» systems in the higher vertebrate forms has undergone alterations both in respect to the extension of the rudiments as well as to the formation and development of their peculiar parts.‘ This has happened first of all as a result of the different physiological demands that the organism in particular cases has made on these organ systems, and secondly in consequence of those changes of situation the various organs have, in various cases, suffered on account of the increasing distribution of labour and specialisation in functions. During the ontogenetic development in the higher Vertebrata only more or less obvious reminiscences of the depicted primitive condition can be expected. But this is a great help: at researches in higher animals, and especially in the human being, for according to modern evolutionary thought we are entitled to assume that each and every part of the primitive condition of an organ system in the higher stages can, when needed, form parts of Organs which perform similar physiological functions as itself.


These views appear with uncommon obviousness when tracing the development of the excretory system. In the ascending Vertebrata three successive excretory organs are met with—the pronephros, mesonephros, and metanephros; the first named has a very intimate connection with the genital system. In order to obtain a correct understanding of this connection it is of capital import to be in a position to regard these three systems as serial divisions of an entire segmental apparatus, the various divisions of which can be compared with one another and be regarded as homologous. For my present purpose it is of special import that from the above one should be able to ascertain the relation existing between those parts which in the highest animal forms assume the building of the urogenital connection and the corresponding organs in both phylogenetically and ontogenetically earlier stages, and by settling the phylogenetic significance of these to interpret inversely the former.


The nephrostomal duct unites the body cavity at the nephrostome with the Bowmanian capsular cavity and is together with the latter developed from the embryonal part of the pronephros, called by Felix “tubulus complementarius ” or “ Ergfinzungskanéilchen.”


A fortunate incident induced me to enter on a closer study of the genesis of the urogenital connection and the female genital passages. About six years ago, while cutting the adnexa of a seven months’ old female embryo in series for another purpose, I found on both sides, and on the left especially well developed, the following anomalous conditions: From the chief furrow of the fimbria ovarica a side fimbria with a deep middle furrow branched out to the anterior surface of the ligament. This soon deepened into a closed epithelial channel towards the middle of the ligament tissue. To the right it contained about 600 p. in a medial direction to the nearest vicinity of the rete ovarü, with the tubules of which it entered into a solid string-formed epithelial connection. To the left I was able to follow a similarly shaped duct extending about 150 p., also running in a medial direction. Here this duct divided into two thinner parallel epithelial channels. One of these branches ended about 300 p. from the dividing point; the other again turned off somewhat downwards towards the mesovarium and joined the rete tubules through a lumen-carrying by—channel about 200p. from the diverging point. The epithelial channel itself extended 950a in a medial direction reckoned from the connecting channel and ran on the side of the rete but distinctly separated from the same. During its progress it entered into three partly solid, partly lumen—carrying, string-formed combinations. with the epithelial tubules of the rete. At its medial end and with retained lumen the channel was united with an epoophoron tubule. Medially the rete ovarü joined two other adjacent epoophoron tubules through partly lumen-carrying strings.


Besides these channels on both sides in the vicinity of their mouths other anomalous formations appeared, from whose form one could immediately conclude that they would give rise to typical so~called appendicular formations.*

More diflicult, however, was it to interpret the described channels, and in this I succeeded, as I believe, only about four years later. As a guidance it was possible to ascertain that the channel on the left mediated an urogenital connection, 11.6., it combined the tubules of the mesonephros with tubules of the rete ovarü, which in its turn were connected with the medullary cords of the ovary. De facto, similar channels have been found in various lower vertebrata in a somewhat different form and stage of development, for instance, in some Pisces, Batrachia, and even the channels and appendicular formations have already been figured by me in Anatomische Hefte and Archives de Biologie, l.c. VViehmann:

Reptilia. The well-known authority on this subject, Felix,” has called the_corresponding channels in these classes “ Nierenrandkanal” (kidney-border channel). Moreover, he has pointed out that in some orders of Pisces this channel reaches such a degree of independence that in its distal end it has grown even as far as the cloaca, and through this a so—called secondary ductus deferens has been formed which is reserved to carry off the genital products. On account of this, the primary ductus deferens (“primarer Harnleiter” of the Germans), which is in connection with the mesonephros, is reserved solely to let off the excretion products of the kidney tubules of the mesonephros, and the organism has attained its purpose, the genital cells having during their progress from the reproductive gland to the surface of the body evaded the injurious influence of the excretion products. The same tendency may be further traced in all higher Vertebrata, and this necessity has been attained in different ways and most completely in the urogenital connection of the higher Vertebrata and in the formation of a special conducting passage for the female genital productsthe Müllerian duct.


Referring to the independence of the “ Nierenrandkanal,” and basing his Opinion on theoretical reasoning, the reviewing of which would carry me too far from the main question, Felix has suggested (l.c. p. 833) that the Mtillerian du-ct may be derived from the “ Nierenrandkanal ” observed in lower animals. And this effort, as Felix himself says, “ Versuch einer Deutung,” is so far the only attempt that has been made to give an explanation of the phylogenetic significance of the Müllerian duct. As I already mentioned at the outset one has, as a rule, been contented to state that in higher animals the Müllerian duct appears as a plate of “ thickened peritoneal layer ” at the cranial lateral surface of the Wolffian body.


The first impression of the anomalous “ Nierenrandkanal ” in the human foetus, which I observed to be in open and continuous connection with the Müllerian duct, was that this discovery was an important support to Felix’s hypothesis. This, however, does not turn out to be the case when one considers the result with reference to the genesis of the rete, which I obtained on the basis of studies of the embryonic material placed at my disposal at Bonn.“


Combining my observations with discoveries made by other and earlier authors and with theory, I came to the conclusion— differing from the opinions of earlier authorities—that the rete tubules in Mammals neither grew out from themesonephros tubules nor from the medullary cords, but differentiated in loco from the primary mesenchyme, posteriorly to join both the mesonephros tubules and the medullary cords, thus efiecting the formatron of the urogenital connection.


Felix likewise arrived, simultaneously, at a somewhat similar conclusion, of which one is convinced by studying Keibel and Mal1’s Manual (vol. ü, p. 913), which had not been published at the time of my researches in Bonn. But when Felix derives the rete tubules from the epithelial nucleus of the indifferent reproductive gland (“Von dem Epithelkern der indifferenten 196 Journal of Obstetrics and Gynaecology


Keimdrtise ”), he agrees more closely with those who in the rete tubules see a product of the genital tissue. From reasoning which cannot here *2 be reproduced in detail, I derive the rete tubules as well as the tubo—rete—epoophoron channel, already explained, and the “Nierenrandkanal” of Felix (the two latter being merely channel-formed anastomoses between the rete tubules) from the aforesaid tubulus complementarius, “ Ergünzungskan'ailchen,” which in the complete pronephros segment in the earliest forms of the vertebrata connect the peritoneal and Bowmanian capsular cavities (cf. fig. I). In the higher Vertebrata this cell material is mostly latent, as the pronephros disappears early, but secondarily it differentiates from the primary mesenchyme, so that it becomes the connecting link between either the reproductive gland or the abdominal cavity on one side and on the other the mesonephros. Similarly, in the earlier stages of the Vertebrata and in the above mentioned and figured primitive condition, it connected the former two with the pronephros (cf. figs. I and 2).


In higher animals, as previously stated, these rete tubules are, as a rule, directly differentiated in loco in the mesenchyme tissue without any continuity with the peritoneal epithelium.


At times, however, especially at the cranial end of the urogenital ridge, the primary connection between the peritoneal layer and parts of the tubulus complementarius are developed, and then a string or channel—formed epithelial connection between the peritonezil cavity and the rete and mesonephros tubules may be observed.


Observations of such a connection between the peritoneal cavity and the rete tubules are, up to the present, only to be found in the author's material (vi7.., three cases; c.g., fig. 2). An open connection between the peritoneal cavity and the mesonephros tubules has earlier been discovered (the cases noted by Luschka,” Roth 1" (cf. fig. 3), von Winiwarter,” and myself). Thirdly, there has likewise been observed a co—existent connection of the peritoneal cavity, the rete tubules and the mesonephros tubules through a single channel system. A similar observation has been made by von Winiwarter and Sainmont and by me in three cases (e.;:., the tubo-rete-epoophoron channel in the seven months’ old foetus above described and in fig. 4.) This third combination may be supposed as having originated from a tubulus complementarius which firstly has preserved its primary connection with the peritoneal layer and secondly has secondarily entered into communication with the other rete tubules, which at last have formed the ordinary connection with the mesonephros tubules.


Now it is to be observed—and in this lies the reason which obliges me in this discussion on the genesis of the genital duct to give a review of researches on the genesis of the urogenital connection—that the connecting channels, to which I have earlier drawn special attention,” join the peritoneal cavity as a rule on the fibria ovarica. This fact is proved by all the reliable cases described in literature, and also by all the ten cases I have Come across during my studies in young human and sometimes other mammal embryos (cf. figs. 2, 3, and 4). This discovery led me to enquire into what explanation this regularity admits.


As I recently mentioned, I interpreted these connecting channels as homologous with the rete tubules and hence with the tubulus complementarius. Their mouths at the peritoneal end should therefore be regarded as homologous with the nephrostomes of the tubulus complementarius (figs. I and 2). Thus these observations prove a regular relation between the epithelium of these nephrostomes and the epithelium of the Mitllerian duct. I therefore formulated the following hypothesis: In the same way as~according to Felix’s suppositi0n—the “ Nierenrandkanal ” originates through an anastomosis formation between the middle parts of the rete tubules or tubulus complementarius, the rudiment of the Müllerian duct generates through a fusion of the nephros— tomal epithelium of these, and similarly as the “Nierenrandkanal” in some Pisces can grow independently as far as the cloaca in order to form a new conducting passage for genital products, so also has the rudiment of the Müllerian duct emancipated itself in the phylogenesis and grown down to the cloaca.


In order to understand better the reasons of the development of this organ form in the phylogenesis, I adopted the following line of thought. During some early phases of development in the vertebrate, as the female reproductive cells began to increase in size to such an extent that their outlet through the channels of the excretory system (cf. fig. I) was rendered more difficult, the nephrostomes of the tubulus complementarius were irritated through this increase in size and were so forced to form a new and sufficiently broad conducting passage. As the ducts of the excretory system had to fulfil other excretory functions at the same time, they were unable to keep pace with this increase of the female reproductive products. Again, for the male smaller reproductive products, these ducts were still pass-able and at the same time the safest conducting passage, especially since on one side the open connection of these ducts with the peritoneal cavity through the genesis of the urogenital connection became useless and t en disappeared, and on the other the metanephros with special excretory duct was formed.


The conclusion arrived at—that the epithelium of the Müllerian duct may be derived from the epithelium nephrostomale of the tubulus complementarius——is noteworthy, inasmuch as two investigators have discovered a certain connection between the epithelium of the Müllerian duct and the pronephros nephrostomes (H. Rabl 17 in Batrachia and Wilsotn 13 in Reptilia). As the epithelium nephrostomale of the tumulous complementarius shown by me in mammals should be regarded as generating from, and being homologous with, the epithelium nephrostomale of the pronephros, so the discoveries of these investigators coincide with the conclusion to which I have indirectly come by utilising results I obtained from examinations of the genesis of the urogenital connection,


About three years, when coming to the above conclusion, 1 had had no opportunity until that time of studying the development of the Müllerian duct in its earlier phases. Only much later, and then in connection with researches of quite a different nature, viz., a study of the genesis of the so-called appendicular formations (hydatids, fringes of fimbria, etc.) in human embryonal material, did I return to the question of the genesis of the female genital passage. On this occasion I was able to point out an evident and regular connection between the Müllerian duct and a number of epithelial formations situated at the cranial end of the urogenital ridge. Of these I can state that in all probability they are homologous with parts of the pronephros ducts, and appear in quite a rudimentary form in the human being.


As it would carry me much too far if I even began casuistically to give an account of the twenty odd embryos in which I have minutely examined these epithelial circumstances, I must content myself in as few words as possible in reviewing the most important parts of my discoveries which have a direct bearing on the genesis of the Müllerian duct.


The epithelial formations at the cranial end of the urogenital ridge are regularly situated on the back surface of the mesonephros ridge in the environment of the abdominal ostia of the Müllerian ducts, thus in a region which in later foetal phases corresponds with the lateral part of the anterior side of the mesosalpinx. Another obvious circumstance, until now unnoticed, is that in human embryos of from two to three cm. in length the epithelium in this region often is considerably higher than in its vicinity, and continues so in a distal direction up to that place where later the limit between the epoophoron and paroophoron becomes evident. This high epithelium appears also in somewhat older embryos in two partly separated zones (cf . fig. 5).


The first zone of this heightened epithelium (shown red in fig. 5) covers a mesenchyme ridge which in 4oo—5oop. runs in a caudal direction more dorsally and medially as a direct continuation of the diaphragmatic band (unreproduced in fig. 5) of the mesonephros. In its middlemost part it is about 80p. high and 70 p. broad, divided into several ramifications, and in transverse section resembles much a section through a glomerulus. In its cranial and caudal ends this mesenchyme ridge gradually grows narrower and disappears at the same time as its cylindrical epithelium merges into the surrounding epithelium. I have come across similar formations in five embryos whose maximum lengths were about 2, 3, 5, ü, and 22 cm. Although I have not found quite similar formations described in literature, I regard myself as being entitled to interpret these fold formations in human embryos as a kind of exterior glomerulus, as they resemble both in shape as well as in constant localisation those glomus formations which have been found in lower animals. This interpretation did not meet with any opposition at the congress of anatomists held at Greifswald in 1913.


The latter epithelium zone, consisting of cylindrical cells, runs laterally and almost parallel with the former and is somewhat less distinctly separated from the vicinity. It begins from the epithelium of the ostium abdominale tubae and extends as far distally as the first-mentioned zone. Its elevated cylindrical cells differ clearly from the flat epithelium of the surrounding and especially the anterior surface of the mesonephros ridge.


Within the area of this second epithelial zone (fig. 5) and also in later phases on the corresponding part of the surface of the mesonephros ridge, in every case (with the exception of two foetuses, six and eight months old respectively) I have found rather a great number of well-defined epithelial formations, generally in the shape of epithelial bladders or pits, which in the later foetal stages have been gradually transformed into appendicular formations. These in later stages of development have assumed different forms, so that all the various kinds have been represented in my cases : those that are pedunculated and those that are broadly affixed to the ligament, the open appendices and closed hydatids, the fimbria—fringes and the funnel- and cup-shaped so—called “ Nebentuben” (fig. 6). Owing to the fact that during my researches I had at my disposal a complete series of human embryos from about I cm. long to the fully developed foetus—which has never before been the case at earlier investigations of the appendi-cular formations—-—I have with positive certainty been able to derive all the appendicular formations, situated on the anterior surface of the mesosalpinx, from the epithelial formations and, indirectly, from the latter of the above mentioned epithelial zones of the posterior surface of the mesonephros ridge in two to three cm. long embryos (figs. 5 and 6).


Thus, through these observations, the question of the genesis of the appendicular formations is, so far as I am concerned, solved. In order to give an idea of the prevailing uncertainty regarding the derivation of these formations, I take the liberty of quoting an utterance which in 1907 was made by one of the most eminent experts in the evolutionary history, anatomy and pathology of the female genital apparatus. Professor Rob. Meyer,” in an article touching among other things on the formations in question, writes : “ Wie oft solche Anhange aus abgeschnürten Urnierenresten oder Nephrostomen oder abnormen Coelomepitheleinstülpungen oder überzéihligen Müllerschen Trichtern entstehen, weiss man nicht genau. Ein Teil der Hydatiden kann freilich auch aus dem kranialen Ende des Wolffschen Ganges entstehen.” In other words, the genesis in question was, according to Meyer’s opinion, in utter obscurity, and since this statement of his no new observations have been published which might shed light on this question.


Taking into consideration the above briefly described observations, the interpretation of the phylogenetic significance of the appendicular formations totally depends on the explanation given to the epithelial zone on the posterior surface of the mesonephros ridge and to the -cell bladders and invaginations which ap-pear within the former.


When attempting to solve this question the chief interest turns, and naturally enough, on the latter. Even in an embryo of about I cm., in which the rudiment of the Müllerian duct is still in a stage of “ thickened peritoneal epithelium ” without any invagination, I have found inside the zone of this cylindric epithelium similar closed cell bladders at the extreme cranial point of the mesonephros ridge. Still more cranially and in still younger embryos ]anosik,2° Veit,21 MacCallums,22 Tandler,” Von Winiwarter,“ etc., have found similar formations. All these authors, with more or less certainty, have explained these formations as pronephros remnants, and so much the more as in their vicinity they have often believed to have found remnants of exterior glomerulus formations.


A priori it must be taken as a matter of course that if once these formations observed by me have some connection with the nephrogenic tissue—and no other organ system can possibly be taken into consideration—they must either be parts of the channel system of the pronephros or mesonephros. Against the latter supposition the following facts speak. Neither the above-mentioned authors nor I have ever come across remnants of interior glomeruli in connection with these cell bladders and invaginations. Yet, according to Felix,” all mesonephros tubules must form interior glomeruli during their development. Secondly, it must be noticed that the formations in my cases in early stages stand in a regular epithelial connection with the above—described superficial epithelium zone, whereas they have always clearly and by great distance been separated from the mesonephros tubules. Lastly, I beg to remind you of the presence of a formation explainable as an exterior glomerulus in the vicinity of these cell bladders and invaginations. All these circumstances seem to me to tell strongly against the mesonephric origin of these latter.


At any rate I am not readily inclined without further notice with the above-mentioned authors to declare these cell bladders, invaginations and channels as proper pronephros remnants, since the pronephros,* which in man indeed appears in a highly developed form, is considerably more cranially situated and disappears much earlier than these formations appear.


On the contrary I may remind you of the diagrammatic outline of the primitive condition of the urogenital apparatus of the Vertebrata (fig. 1) and draw attention to the coincidently assumed possibility that particular parts of organs developed in earlier animal forms can attain a certain degree of structure as a reminiscence of phylogenetically earlier periods. Bearing these possibilities in view, I have come to the conclusion that the often mentioned epithelium bladders, invaginations, channels and the epithelium zone consisting of cylindric cells, inside of which the former always appear, do not form proper pronephros remnants, but build up a special epithelial blastema, which, however, judging from all circumstances, has stood in a genetic connection with the pronephros and still appears’ in man, during a short period of intra-uterine life, simultaneously and in connection with the initial development stage of the Müllerian duct in a rudimentary form, as a reminiscence of phylogenetically earlier periods. As previously said, I have always found this blastema in regular connection with the ostium abdominale of the Müllerian duct.


Felix has especially called attention to the difficulties of explaining these channel fragments and has expressed doubts as to the right of interpreting them as real pronephros remnants.


Let me again refer to earlier authors’ observations in lower animals. Wilson 26 in 1896 found that the invagination of the Müllerian duct in crocodiles appears in the middle of an elevated epithelial zone which combines the different pronephros nep«hrostomes. H. Rabi” has proved that this invagination in embryos of the frog is built from that cell material which remains over after the degeneration of the second pronepvhros nephrostome.

If, then, with regard to the complete analogy existing between Wilson’s, Rabl’s and my discoveries, I endeavour to homologise the different constituents of the organ parts spoken of (cf. fig. 5), I should be obliged to consider the much-alluded-to cell bladders and channels as homologous with the tubulus complementarius of the pronephros, perhaps also in a measure with parts of the tubulus principalis (cf. fig. 1). Consequently their open ostia within the range of the blastema should be taken as homologous with the pronephros nephrostomes. Thus, I say, only as formations homologous with pronephros constituents, not as real parts or remnants of the pronephros, as this organ in man disappears much earlier after having reached a certain degree of development at the -cranial part of the rudiment.


The blastema itself, which according to Wilson and myself combines the nephrostomes in question, and inside which the Müllerian duct takes its origin, -can be homologised, naturally, only with the epithelium of these nephrostomes, i.e., its cell material is derived from the epithelium nephrostomale of the tubulus complementarius.

According to this line of thought I come at last to conclude that the initial stage of the Müllerian duct, the funnel-shaped epithelial invagination, generates within the area of an epithelial blastema—built up of cylindric cells—which connects a number of ostia homologous with the pronephros situated on the uppermost part of the urogenital ridge.

From the above it will appear that a year ago in connection with researches, through which I endeavoured to explain the genesis of the appendicular formations, I arrived, with reference to the genesis of the Müllerian duct, at quite the same result as that I obtained two years earlier when, with the help of my material from Bonn, I tried to interpret the origin of the urogenital connection. Even then I surmised that the epithelium of the Müllerian duct is homologous with the epithelium of the ostia, which mediate an anomalous -connection between the central furrow of the fimbria with the rete tubules and mesonephros; and these ducts I then derived from the tubulus complementarius.

From these two pieces of work I feel entitled to formulate the following theory : The Müllerian duct in Man and Mammals, as in Amphibians and Reptiles, originates from a diffused epithelial blastema, which in the phylogenesis is derived from the epithelium nephrostomale of the tubulus complementarius of the pronephros.

The fimbria ovarica originates from the cranial part of this blastema and the appendicular formations situated in later stages on the anterior surface of the mesosalpinx from its caudal end. All the appendicular formations existing on the posterior surface of the mesosalpinx are, according to my observations, fragments separated from the fimbria tissue in about the third month of pregnancy. Contrary to the opinions expressed by all earlier authors, I derive likewise all the appendicular formations from this blastema.

Without wishing to enter into a more detailed application of the above theories, I still intend to hint briefly at those questions to which, according to my opinion, they offer a satisfactory explanation.

In the first place the question of the origin of the rete ovarü and the rete testis or corpus highmori. The earlier vindicated opinions that the rete strings were proliferation products of the Bowmanian capsular epithelium belonging to the mesonephros (von i\ühélkovics, von VViniwarter, Saintmont, etc.), or on the other hand of medullary strings or other epithelial constituents of the genital gland (janosik, Coert, Felix, etc.), cannot offer a plausible explanation or point out a phylogenetic basis on which this organ develops in the higher vertebrata. My view meets these requirements, as the rete tubules directly differentiate in loco from the primary mesenchyme and are explained as homologous with the tubulus complementarius, which in all animals where it develops fulfils the same functions, and is the first link between the genital cells of the abdominal cavity and the proper evacuating genital passages.


In connection with this result the earlier and variously solved problems regarding the significance of the tubo-parovarian duct (Roth) or tubo-epoophoron duct (fig. 3) obtain a natural explanation. This, together with the tubo-rete duct (fig. 2), proved by me, and the tubo-rete-epoophoron duct (fig. 4), studied by von Wini\-sztrter and Saintmont anti myself, are thus differentiation products of the tubules complemeütarius and have a particular site, influenced by earlier processes of development. They are homologous with the rete tubules.

In the second place my comments so far constitute the only explanation of the origin and phylogenetic import of the female genital passage, based on great research material.


In the third place my observations have definitely solved the question of the development of the appendicular formations, hydatids, “ Nebentuben,” fimbria-fringes, etc.,_ from their earliest stages, and in connection with the theory regarding the significance of the Mfillerian duct has given a phylogenetic explanation to the same.


In accession to these results the formerly unsettled tubadiverticular ducts (cf. fig. 6) and the tuba-diverticulav cysts (cf. fig. 7), originating from the former, have been explained as differentiation products of the epithelial blastema discovered by me. They originate in the neighbourhood of the ostium abdominale of the Mijllerian duct through a_tube-formed tnvagination which is then separated from the covering epithelium. they are generally situated on the anterior surface of the mesosalpinx as the typical appendicular formations in a zone which corresponds to 51153) area of the blastema in 2-3 cm. long embryos (cf. figs. 5 an .


As an illustration of the possibility—through the help of my conclusions—of giving a plausible explanation of anomalous formations which before could scarcely have obtained a satisfactory explanation, I cannot omit mentioning a case briefly which I dissected while acting as officiating assistant at the Helsingfors Pathological Institution about two years ago. It was an almost fully developed female foetus born at the lying-in hospital. The beating of the heart ceased to be heard about five minutes before birth. From an exterior inspection nothing abnormal was noticeable. The lungs were quite atelectatic; in the heart, thymus, liver and spleen nothing abnormal was to be seen. In spite of persistent searching the kidneys and ureters could not be found. The bladder was small and empty; the ureter mouths were wanting. In place of the uterus a small bipartite tissue mass without lumen was present which seemed to resemble a rudimentary uterus bipartitus. The tubes could not be discovered, but between the second and third lumbar vertebrae highly developed fibria or ostium formations were found, which were connected with the cranial end of the ovaries through well developed fimbriae ovaricae. The ovaries were extraordinarily long (left about 2.5 cm., right about 4 cm.), narrow, and thin.


To study the Müllerian ducts I cut both adnexa in series (figs. 7 and 8 demonstrate the circumstances roughly and diagrammatically). Only to the left a proper ostium abdominale tubae and a rudimentary beginning of the Müllerian duct is seen. Through two superfluous ostia (on the genesis of which I cannot here enter into detail) it is in connection with the ligament surfa-ce, on which somewhat farther off appear two appendicular formations : one pedunculated, the other embedded in the ligament. The cavities of these formations are in open connection with the peritoneal cavity through two and three ostia respectively. The cylindric epithelium of the unstyled formation passes through one of these ostia into the surface of the ligament and to some extent covers it. In principle these appendicular formations in no wise differ from the “ Nebentuben.” On the right there is one welldeveloped fimbria ovarica only; no ostium abdominale tubae can be found. But in that place, described as that where the Müllerian duct is developed on the left side, there are two closed epithelial cysts, rather deeply submerged within the ligament tissue. These cysts in attitude and form most clearly correspond to the tubodiverticular cysts.* These almost symmetrically situated different appendicular formations find their full explanation only through the supposition that the growing of the epithelium——the so-called Müllerian epithelium——when beginning to form the Müllerian duct has ceased and its material has gone to their development. Quite similar formations arise from the earlier mentioned blastema—— owing to the prevailing laws, during embryonal life, for the proliteration of this epithelium and the connective tissue muscle layer belonging to it, whose tendency is to bring about folds and invaginations and in some degree to outdo the vicinity in growth. The described epithelial formations in this case of aplasia of the Müllerian ducts are thus typical products of the proliferation of the Müllerian epithelium.


The epithelium in these four formations is quite similar to that found in typical appendicular formations. The epithelium is in all respects likewise the same as that of the various parts of the Müllerian duct. I have already minutely described these epithe1ia in a paper in Archiv fur Gynükologie, Bd. 102, 1914 (“Uber das Epithel der Anhangsgebilde des Ligamentum latum ”).


References

1. Müller, Johannes. “ Bildungsgeschichte der Genitalien.” Düsseldorf, 1830.

2. Meckel, J. Fr. Handbuch der menschlichen Anatomic, Bd. iv, 1820.

3. Kobelt, G. L. “ Der Neben-Eierstock des Weibes.” 1847.

4. Bornhaupt, Th. “ Untersuchungen über die Entwickelung des Urogenitalsysteins beim Hünchen. Diss.” Riga, 1867.

5. Waldeyer, W. “ Eierstock und Ei.” Leipzig, 1870.

6. Janosik, J. “ Histologisch-embryologische Untersuchungen fiber das Urogenitalsystem.” Sitz. Ber. d. math. naturw. Klasse der Akad. d. Wiss., Bd. 91, abt. üi, 1885.

7. Von Mihélkovics, G. V. “ Untersuchungen fiber die Entwickelung des Harn- und Geschlechtsapparates der Amnioten.” Intemat. Monatschr. für Anat. und H1'$tol., Bd. 2, 1885.

8. Von Winiwarter, H., et Sainrnont, G. “ Nouvelles recherches sur Povogenese et Porganogenese de l’ovaire des mamrniferes (chat).” Archives de Biologie, T. 24, 1908, s. 423.

9. Felix, M. “ Die Entwickelung der Harn und Geschlechtsorgane. Keibel und Mall.” Handbuch der Entwickelmzgsgeschichte des Menschen, Bd. ü, 1911.

10. Felix, W. “ Entwickelung der Ableitungswege der beiden Keimdrüsen.” O. Hertwig. Handbuch der "uergl. u. experim. Entwz'ckel1mgslehre der Wirbeltiere, Bd. üi, Teil LS, 819. Jena, 1906.

11. Wichrnann, S. E. 1.c. Anat. Hefte, S. 690.

I2. Wichmann. 1.c. Anat. Hefte, p. 684.

13. Luschka, H. “ Die Appendikulargebilde.” Virchows Archz'v., Bd. vi, 1854.

I4. Roth, M. “ Uber einige Urnierenreste beim Menschen. Festschrift zur Feier der Univ. Würzburg.” Basel, 1882.

15. von Winiwarter, H. “ La constitution du corps de Wolff et le développement du canal de Müller dans 1’espéce humaine.” Archives de Biologie, T. 25, 1910.

16. Wichmann, S. E. 1.0. Anatomische Hefte, pp. 687 and 692.

17. Rabi, H. “Uber die Vorniere und die Bildung des Müllerschen Ganges bei Salamandra maculosa.” Arch. ffir mikr. Anat., Bd. 64, I904.

18. Wilson, G. “ The Development of the Ostium Abdominale Tubse in the Crocodile.” Anat. Anzeiger, Bd. 12, I896.

19. Meyer, Rob. “ Zur Kenntnis der kranialen und kaudalen Reste des Wolffschen Ganges beirn Weibe, mit Bemerkungen über das Rete ovarü, die Hydatiden, Nebentuben u.s.w.” Zentralblatt für Gynzikologie, 1907, Nr. 7. Wichmann: Origin of the Female Genital Passages 205

20. Jano-sik, J. “ Zwei junge menschliche Embryonen.” Arch. f. unter Anat., Bd. 30, I887.

21. Veit, O. “ Uber das Vorkommen Von Vornierenrudimenten und ihre Beziehungen sur Urniere beim Menschen Marb Sitz Ber.” I909.

22. MacCallum, J. B. “ Notes on the Wolffian Body of Higher Mammals.” Amer. Journ. of Anatomy, vol. i, 1902.

23. Tandler, J. “ Uber Vornierenrudimente beim Menschlichen Embryo.” Anat. Hefte, Bd. 28, 1905.

24. von. Winiwarter, H. 1.c.

25. Felix, W. 1.c. “ Handbuch der Entw.-gesch. des Menschen von Keibel und Mall.” Bd. ü, 1911, S. 777.

26. Wilson, G. l.c.

27. Rabl, H. l.c.

Explanation of Figures

Figure 1. Diagrammatic outline of the primitive condition of the vertebrate urogenital system according to the diagrams of Felix. To the left the mesenteric insertion and on either side the posterior wall of the body cavity (light grey) inserted with genital cells (black). The red zone marks the exterior glomerulus or glomus. Farther to the right, pronephros nephrostomes connected through nephrostornal channels with the Bowmanian capsular cavities. Each of these contains an interior glomerulus. The epithelium of the nephrostomal channel and the capsules of Bowman (black and white) are differentiation products of the tubulus complementarius, which again is built up of the lateral part of the lamina urogenitalis or “ Ursegmentstie1” in the earliest enibryonal stages. Still more to the right follow tubulus principalis and the common conducting passage, at the same time the primary excretory duct and the primary ductus deferens.


Figure 2. Diagrammatic graphic reconstruction of a 6.2 cm. pig embryo (Professor Bonnet’s collection). To the left the genital gland, testis (dark grey). From its cranial end the fimbria testis runs to the ostium abdominale of the Müllerian duct. In its chief furrow there are three ostia connected with the well developed rete testis (white net) through partly lumen-carrying epithelial bridges (black and white).* On the opposite side of the rete the Malpighian corpuscles of the mesonephros are in epithelial connection with the rete tubules through the Bowmanian capsular epithelium. There is thus a connecti0n——mediated through the rete tubules———of the mesonephros tubules with the peritoneal cavity on the middle furrow of the fimbria. Those parts of the connecting system originating from the tubulus complernentarius are as in fig. I in black and white.


Figure 3. The well—known tubo-parovarian duct of a 19 years old virgin, published by Roth, 1882. There are reasons for supposing that its branching towards the ovary and rete (not here reproduced) consists of parts of rete tubules.


Figure 4. Diagram obtained through approximate graphic reconstruction. From the fimbria furrow a tubo-rete-epoophoron duct goes out, being at its commencement connected through two ostia with the ligament surface in a region where the peritoneal layer is formed of cylindrical cells (not shown).

Wichmann. l.c. Anat. Hefte, figs. 19-25. In its middle the duct is in open communication with an epoophoron duct; at its medial end it disappears among the rete tubules. Somewhat above there are two typical hydatids superficially embedded in the ligament. One of these has retained a certain connection with the epithelium of the Müllerian duct, as a flap of the fimbria tissue continues along the surface of the ligament as far as that place where the epithelium of the bladder seems recently to have been separated from the surface. An evident epithelial connection is, however, no longer noticeable.


Figure 5. A diagrammatic drawing of the epithelial formations on the posterior surface of the urogenital ridge in a human embryo of about 3 cm. length. To the left the sex gland and ligament insertion in the back wall of the body cavity. The Müllerian epithelium on the fimbria and the two epithelium zones consisting of the cylindric cells well developed. The red zone denotes the site of the exterior glomerulus formation; the light part with the two typical cell bladders, on the other hand, the caudal part of the outspread blastema, from which originate the Müllerian duct, the appendicular formations, etc.


Figure 6. Diagrammatic reconstruction obtained from a series of an 18 cm. human foetus. One can first of all follow towards the anterior surface of the mesosalpinx a tubo—diverticular duct about 400 9. long which is superficially embedded in the ligament and which begins. at the ostium abdominale tubae. In its medial end it comes into Contact with the locally somewhat elevated peritoneal layer (unshown). Beside it runs. a partly channel-shaped formation appearing generally as a surface epithelium zone built up of cylindrical cells. Its progress totally corresponds with that of the blastema zone reproduced in fig. 5. In direct continuation of these two formations in a medial direction and downwardly on the anterior ligament surface follow, at intervals, five typical appendicular formations representing both open and closed, styled and unstyled hydatids and “ Nebentuben.” Between them the peritoneal layer is often unequally elevated and sometimes assumes the character of the cylindrical epithelium (not shown). At the same time the surface shows numerous elevations and invaginations in the vicinity of these formations.


Figures 7 and 8. Diagrammatic drawings of the extension of the Müllerian epithelium in a new-born female child. The description of the figured formations is to be found in the text.


In the diagrammatic drawing the two ostia have been figured above the channel, although they should be in connection with the fimbria tissue below. This is in order to avoid in the drawing the confusion with the rete. Thus these openings lie de facto in the fimbria-tissue (cf. the description of Case 8 and figs. 20-22 in Wichmann, l.c. Archives de Biologie).

-1- Cf. figs. 10-19 in Wichmann, S.E. “ Uber die Bedeutung des Müllerschen Epithels, nach Studien am Menschen.” Verhandl. der Anat. Gesellschaft. Versamml. in Greifswald, 1913, S. 139.



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