Book - Russian Embryology (1750 - 1850) 12
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Blyakher L. History of embryology in Russia from the middle of the eighteenth to the middle of the nineteenth century (istoryia embriologii v Rossii s serediny XVIII do serediny XIX veka) (1955) Academy of Sciences USSR. Institute of the History of Science and Technology. Translation Smithsonian Institution (1982).
Publishing House of the Academy of Science USSR
Translated from Russian
Translated and Edited by:
Dr. Hosni Ibrahim Youssef # Faculty of Veterinary Medicine Cairo University
Dr. Boulos Abdel Malek
Head of Veterinary Research Division
Arab Republic of Egypt
The Smithsonian Institution and the National Science Foundation, Washington, D.C, by The Al Ahram Center for Scientific Translations 1982
The Smithsonian Institution and the National Science Foundation, Washington, D.C by The Al Ahram Center for Scientific Translations (1982)
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Chapter 12. The Study of the Embryonic Membranes of Mammals - The Investigations of Ludwig Heinrich Bojanus
Wolff frequently mentioned but did not give a comprehensive description of the embryonic membranes and organs. Later authors tried to explain the nature and reciprocal situation of the mammalian embryonic membrane and embryonic organs â€” Meckel, Cuvier, Dutrochet, Oken, Emmert, and others. The most significant attempts were undoubtedly, however, those investigations accomplished at the beginning of the nineteenth century in Russia, at Vilna University by Professor of Veterinary and Comparative Anatomy Ludwig Bojanus. 1
Ludwig Bojanus (1776 - 1827), born in Elzas, accepted in 1806 an offer to occupy the department in Vilna, where he spent the last twenty years and more of his life. Bojanus was a brilliant, talented lecturer and investigator. Besides his work in veterinary science, Bojanus published a number of reports on the comparative anatomy of molluscs, annulated (annelida) and flat worms, fish, reptiles, 2 and mammals, and also investigations of vertebrate embryology. In his special work, his capability as an extraordinarily thorough investigator and acute ohseryer is recognized. He also undertook more theoretical investigations, as seen in articles on the yertebral origin* of the skull and in his academic lectures, particularly in his introduction to comparative anatomy. In this last work, he discussed ideas on the reciprocal relationship of organisms. This gave B. E. Raikov the basis for including Bo j anus in the list of Russian evolutionists and forerunners of Darwin. (65)
1. Biographical data concerning Bojanus is contained in Raikov, RUSSIAN BIOLOGISTS AND EVOLUTIONISTS BEFORE DARWIN
U952) , which gives the most complete bibliography of his works .
2. From the anatomical work of Bojanus. His work "Anatomy of the European Tortoise" (ANATOME TESTUDINIS EUROPAEA, Vilnae, 1819 - 1821) is especially significant. The more detailed descriptions of the structure of EMYS ORBICULARIS are furnished with wonderful drawings by the author. This work received the enthusiastic opinion of Cuvier and Oken.
Bojanus 1 embryological work considered the embryonic membranes and embryonic organs of the vertebrate animals, mainly mammals. His first work, accomplished in 1813 and published in 1815,3 was entitled "On the Fetal Membranes of Dogs, Mainly concerning the Allantoic Membrane." The author sought to address the unclear question of whether the amnion was surrounded from all sides by the allantois. He effected detailed and accurate description of canine fetal membranes by applying a method of opening which guaranteed the membranes' completeness and retained their normal location.
According to Bojanus, the fetus extracted from the uterus with its membranes has a cylindrical shape and is covered on all sides by the chorion, in the middle, above the surface of the chorion, a dominant zone of thicker fibrous vascular tissue is limited by a fold-like border. This zone, which is near the internal surface of the uterus, is in contact with the maternal placenta. If an opening is carefully cut in the chorion, the fetal fluid does not escape, and consequently its receptacle remains intact.
3. L. Bo janus, "De foetus canini velamentis imprimis de ipsius membrana allantoide , " MEM. ACAD. SCI. ST. PETERSB . , 5 (1815) , p. 3021. This work was later published in German (with indication to the original place of publication) in the journal edited by L. Oken. At the beginning, in the form of a short abstract, was a review of a number of comparative anatomical works. "Verzeichnis meiner Arbeiten in der vergleichenden Anatomie," ISIS, 7 (1817), pp. 876 - 884, attached to the article, L. Bo janus, "Anatomie des Blutegels," ibid., pp. 874 - 876, and then in detail: L. Bo janus, "Abhandlungen uber die Hilllen des Hundefoetus, insbesondere uber dessen Allantoides, " ibid . , 10 (1818), pp. 1616 - 1623.
Ludwig Heinrich Bojanus
Bojanus opened only the external membrane of the chorion, and hence he was able to see the actual location of the embryonic membranes and organs. His predecessors had not taken the necessary precaution's and had come to a number of incorrect conclusions, in particular to the determination that the umbilical sac is located inside the allantois. Bojanus accurately determined the shape and topography of the umbilical vesicle (tunica erythroides, vesicula umbilicalis) . The latter has the shape of a folded, reddish Cdue to a great number of vessels), thin stem which extends from the umbilical cord and is stretched between the main vessel stems which connect the umbilical cord with the belt of placenta. The umbilical vesicle spreads along the fetus to the end of the fetal sac, where it is joined with chorion Cand not with the amnion, as was thought by Needham and Oken) . Daubenton likewise did not understand the nature of this formation and wrongly considered it to be the allantois, which is not surprising because he did not find any connection with the urinary bladder. Besides the umbilical vesicle, at this stage the allantoic canal appears, though its detection is not easy.
In order to reach the allantois and the amnion, it is necessary to open the internal membrane of the chorion with its thin blood vessels. With careful preparation, the removal of this membrane does not lead to the pouring off of the fetal fluid. Such a careful opening of the internal membrane of the chorion is difficult to accomplish, however, because the deep membranes are firmly attached with it and are very thin.
Successful opening allowed Bojanus to correct the prevailing wrong belief in that time, that the amnion and the embryo are located in the allantoic cavity and swim in the fluid filling it. The displacement of the fetus in the amnion by pressing on it from the outside and by blowing the allantois with air after releasing its fluid through a small cut, allowed Bojanus to determine that the amnion is not surrounded on all sides with the allantois. Instead, the latter forms around the fetus which lies in the amnion.
The results of Bojanus' investigations are summarized in the following manner. The fetus of the dog has four membranes: the amnion, allantois, umbilical sac and chorion. The amnion lies not in the cavity of the allantois, but near the sac formed by it; the amnion is surrounded by the allantois except for a small part. The allantois is provided with a canal which goes to the urinary bladder of the embryo. The umbilical sac lies outside the allantoic cavity; it is not joined with the allantois; its stem is connected with the umbilical cord; and both the free ends of the sac are connected with the chorion. The chorion forms a closed cavity around all the other parts and is composed of two layers, of which the thicker external one is enveloped by the placenta as a belt and is connected with the uterine wall. The internal layer covers the allantois, and the amnion is covered with the allantois. Figure 19 shows the transverse section through the fetus. The scheme shows the topographic relationship of the fetal membranes and their cavities. In explaining the drawing, Bojanus wrote that he omitted the blood vessels and the internal layer of the chorion to make it more clear. It is not difficult to realize that Bojanus succeeded in delineating very accurately the most important relationships between the individual embryonic membranes and the organs.
In 1817 and 1818 Bojanus published three reports on the allantois and the umbilical sac in horses^ and sheep. 5 In the first, he argued with Dutrochet, whose investigations Bojanus saw as creating greater confusion than they eliminated. Dutrochet indicated that the umbilical sac, with the fetus and the amnion covering it, is included in the allantoic cavity. He considered also that in the human fetus, as in the mare fetus, the allantois fits closely to the entire internal surface of the chorion. Bo j anus considered the first of these to be disproyed by his work published in 1815,
4. L. Bojanus, "Allantoides und vesicula umbilicalis des Pf erdef oetus . Bemerkungen aus dem Gebiete der vergleichenden Anatomie," RUSSISCHE SAMMLUNGEN FUR NATURWISS. U. HEILKUNST, Riga u. Leipz., 2 (1817) preprinted in ISIS (1818), pp. 1426 - 1427. L. Bojanus, "Uber die Darmblase des Pf erdef oetus , " ISIS (1818), pp. 1633 - 1636. In this last work a teaching scheme is included for the reciprocal relationship of the embryonic membranes and organs, similar to that given above for the dog embryo.
5. L. Bojanus, "Uber die Darmblase des Schaafsf oetus, zum Beweise, dass die vesicula umbilicalis mit dem Darm unmittelbar zusammenhangt," ISIS (1818) , pp. 1623 - 1633; also in Meckel's ARCH. ANAT . PHYSIOL. (1818).
Figures 19 - 21. Illustrations from Bojanus' work.
19 transverse section of a dog fetus; 20 - discorded membrane of a human fetus; 21 - yolk duct of an adder.
The second Bojanus correctly considered inaccurate because the embryonic organs of man and horses have different structure. In order to explain, Bojanus gaye the following description of the topography of the fetal membranes and embryonic organs of horses. The fetus is covered with the amnion, which with the umbilical vessels goes out from the allantoic duct and widens, forming the voluminous allantoicsac. This sac bends around the amnion and lines the entire chorion, with the exception of that place where the blood vessels go out. "Therefore," Bojanus said "the amnion and its fetus lie in the allantois exactly as the intestines in the peritoneum." This accurate comparison shows that the intestines lie not in the cavity of the peritoneal sac, but outside it and are covered with folds of the peritoneum. Bojanus concluded with the following words: "The amniotic sac does not swim in the allantoic fluid entirely; the allantois and the amnion forms an independent closed sac, located between the amnion and chorion and next to the external wall of the amnion and the internal wall of the chorion." This, according to Bojanus, is characteristic for the fetus of the horse as well as for other mammals â€” dogs, cats, and ruminants.
In another place (ISIS, 1817, p. 877), Bojanus entered into controversy with Emmert. Emmert stated that the duct of the umbilical sac Cyolk duct) is formed apparently only at the end of development, being formerly unconnected with the cavity of the intestinal canal. Bojanus referred to his data, and to what "Wolff had forty years earlier already showed to the contrary, so obviously that the subject could be considered completed."
In sheep embryos Bojanus found basically the same situation as in the embryos of dogs and horses. In an article about the embryonic membrane and organs of sheep, Bojanus determined that the allantoic duct entered into the posterior end of the peritoneal cavity. Near the duct, both the umbilical arteries and the umbilical veins extended into the peritoneal cavity, divided, and turned toward the liver. The stem of the umbilical sac in the embryonic body was directed straight toward the intestinal canal.
In 1820 Bojanus again returned to the embryology of dogs and gave an anatomical description of a twenty-four-day-old fetus and its embryonic membranes. 6 A year later in ISIS, Bo j anus considered the membranes of the human fetus. 7 in that work he is considered to have corrected the main mistake in the description of the sloughed-off membranes, which remained from Hunter's time. Bo j anus showed that the ovum, going out from the Fallopian tube, passes between the wall of the uterus and the sloughed-off membrane. By increasing in size, it separates the membrane from the uterine wall to the extent that the hillock which is covered with the sloughedoff membrane protrudes increasingly into its cavity. In the place where the fertilized ovum contacts the uterine wall, the maternal placenta forms. In the same place, the uterus forms a new sloughed-off membrane [Bojanus calls it decidua serotina) , in which the vessels grow from the chorion and the maternal placenta. And thus, at the beginning the decidua bends through the fertilized ovum and covers it only in those places where it is not in contact with the uterine wall. The end of the ovum appears to be surrounded with the sloughed-off membrane. Schematic illustrations (Figure 20], further elucidate the description.
In the same ISIS article is a small note,** addressed to the editor of this journal, L. Oken. There Bo j anus cited Oken's unjustified attack and proposed that Oken should more accurately formulate his point of view on the nature of the sloughed-off membrane. Bojanus' dissatisfaction is entirely justified, because against Bojanus' accurate observations Oken had opposed only the dim ideas of Naturphilosophie.
A year later Bojanus published a work in which, by extending his previous material, he gave a description of the relationship of the umbilical sac to the membranes in the hare. 9
Bojanus, "Observatio anatomica de foetu canino 24 dierum ejusdem velamentis," NOVA ACTA ACAD. LEOPOLD . -CAROL . , 10 (1820) , p. 139.
Bojanus, "Ein Wort iiber das Vernal tniss der membrana decidua und decidua reflexa zum Ei de menscher lichen Embryo," ISIS (1821), pp. 268 - 271.
Bojanus, "Anfrage und Bitte wegen der membrana decidua," ISIS (1821) , p. 1174.
Bojanus, "Uber die Darmblase des Haasef oetus , " ISIS (1822), pp. 1228 - 1230.
Not being restricted to investigations on mammals, Bo j anus performed his basic conclusions also on reptile embryos, mainly on the adder (Coluber berus , or , according to the present systematic terminology, Vipera berus L.}. Eramert confirmed that in the reptile embryo the yolk duct is not present, i.e. the duct connecting the yolk sac with the intestine.
Concluding from the comparative embryological work, Bo j anus doubted that this observation was correct; his investigations led to other conclusions. The main part of his work consists of thorough drawings with detailed explanations. 10 The articles are summarized in the following:
- In the fetus of Coluber berus there is a yolk duct;
- this yolk duct is connected with the intestinal canal not far from the origin of the appendix, i.e. it has the same topographic relationship as the horse embryo;
- the yolk-mesentery vessels are situated primarily as in other animals.
Of the illustrations accompanying this work, Figure 21 is particularly remarkable. It shows the connection of the yolk duct with the intestine at the early stage of intestinal development when parts of the intestinal canal are still undifferentiated. The yolk duct enters a region between the stomach and the beginning of the intestine. Also shown is that connection of the yolk-mesentery artery with the descending aorta and the yolk-mesentery vein with the flooding vein.
This short account of Bojanus' embryological investigations confirms that he succeeded in settling a number of important questions about the structure and reciprocal situation of the embryonic membranes and embryonic organs in mammals and reptiles. The results of his distinct investigations led him to argument with known authors of that time, especially with Cuvier. Only later was it determined that Bojanus 1 descriptions and discussions were much closer to the truth.
10. Bojanus, "Dottergang im Foetus des Coluber berus," ISIS CI 818), pp. 2093 - 2094.
In embryology Bojanus could be considered a continuation of Wolff, of whose work he always spoke with great respect. In the epoch preceding the appearance of the classical work of Pander and especially Baer, the investigations of Ludwig Bojanus undoubtedly had remarkable importance.
Cite this page: Hill, M.A. (2024, February 21) Embryology Book - Russian Embryology (1750 - 1850) 12. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Russian_Embryology_(1750_-_1850)_12
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