Book - Russian Embryology (1750 - 1850) 22
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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 22. Fourth Part of Uber Entwicklungsgeschichte - Studies on the Development of Man
The final, fourth part of UBER ENTWICKLUNGSGESCHICHTE 1 was published fifty-one years after the appearance of the previous parts. Because of conditions which prevented this work from appearing at the proper time, L. Stieda stated the following: "I am publishing the termination of work which the scientific world has awaited for more than fifty years."
It is known that Baer's study of the history of animal development remained unfinished. The publishing of the second part, begun in 1829, stopped for five years due to incompletion of the manuscript. The publisher Borntrager, in Konigsberg, waited three years for the promised completed work, and finally published the incomplete second volume without a preface, table of contents, or explanation of the tables.
When Baer left Konigsberg in October 1834, the manuscript of the final part was, apparently, already prepared. He intended to compare his results of the study of human embryos with the analogous observations of other authors upon his arrival in Petersburg. He sent extracts of his manuscript from Konigsberg to Siebold, who published them under the name "Observations on the History of Development of Man. Portions from a letter to the Publisher. "2 In this letter Baer wrote:
1. Karl Ernst von Baer, UBER ENTWICKLUNGSGESCHICHTE DER THIERE. BEOBACHTUNG UND REFLEXION. Zweiter Theil. Schlussheft. Herausgegeben von Prof. Dr. Ludwig Stieda, Konigsberg, 1898. v + 84 pp. After Stieda' s preface on the second "title" page appeared: "IV Studien aus der Entwickelungsgeschichte des Menschen."
2. Baer, "Beobachtungen aus der Entwickelungsgeschichte des Menschen," Aus einem Schreiben an den Herausgegeber JOURN. FUR GEBURTSHILFE, 14 (1835), pp. 400-411.
My observations on the history of development of man . . . are intended for the second volume of the book. I made up my mind to publish the history of development now before changing my place of resistance. However, these materials remained unfinished for a long time because I could not complete description of the development of the lower classes of animals (111) . . . therefore I am not confident of completing this manuscript in five years.
When Baer arrived in Petersburg and wanted to resume the work, he did not have the necessary books, because his own library still was not available. During resettlement he did not take his library with him and received it only a year later in late autumn of 1835. He began unpacking the books and putting them in order in the winter of 1835/36. Since Baer could only outline his section on man, Borntrager grew impatient and published the second volume incomplete. Following this, Baer left the manuscript unchanged and turned to other scientific work. In Ms autobiography he wrote: "I am sorry, that in the hope of filling these gaps in the history of the development of invertebrates I did not print the other work, 'The Special Investigation of the Earlier Stages of the Human Ovum'."
Stieda wrote that "directly after Baer's death in November 1876, when I was busy putting his remaining literature in order, I found this manuscript together with the titled volumes." Stieda could not devote time to the manuscript then either and only prepared it for press twelve years after Baer's death. The published text, as Stieda wrote, exactly repeats the contents of the manuscript. The publisher did not make any changes or additions but only put Baer's outlines next to the text. Explanation of the drawings and Tables IV-VII published in the second volume of UBER ENTWICKLUNGSGESCHICHTE were without explanation. The first two tables (IV and V) relate to the text of the second volume, and the other two (VI and VII) illustrated the final fourth part. Stieda included in his preface the suggestion that the reader understands that the work had been written fifty years earlier. This note of Stieda' s was more significant for the reader of the second half of the twentieth century since more than hundred years had elapsed after Baer's writing on his embryological work.
The contents of Baer's work do not require a detailed account. The work is a collection of materials for the future connected with the history of the human embryo. Baer himself wrote in the introduction that his suppositions were to be considered as observations relevant to the study of the history of human fetus, and not as complete descriptions of the later stages of human formation. He noted later that the earlier stages of different human ova so strongly differed from each other that no investigator could be absolutely correct in his observations, but that which was considered normal, and that which was considered a deviation from normal was beginning to be made clear. Therefore, Baer continued, it is very important that one observer has the possibility to compare a large number of ova. He conveyed his satisfaction with the fact that he, by investigation, could confirm that aborted ova are frequently abnormal.
Baer's descriptions of human fetuses follow their ages, which can be judged by data of a preliminary case study and by features of the embryos and their membranes.
Unquestionable interest is represented by case 1, relating to an extremely early stage. Because early diagnosis of pregnancy is very difficult, Baer considered it necessary to include for this case the following data concerning the duration of pregnancy: "In the summer of 1826 in the Anatomical Institute of Konigsberg the corpse of a servant was obtained, found in Pregel. It was learned that the young girl had spent half a day with a young man eight days earlier. She returned home very sad and anxious. Her death by drowning was not accidental but deliberate. Anatomical investigation showed the presence of a recent pregnancy. I supposed, that the determination of the duration could be considered correct" (p. 5).
On the convexity of one of the ovaries, Baer found a slit-shaped opening of crescent form which was beginning to grow. Cutting the ovary he found there a cavity covered with a yellow mass; from outside the yellow body was covered by a layer of cellular tissue, the outer layer of the capsule of the evacuated Graafian follicle. The uterus was not increased in size, but was somewhat swollen; its anterior wall was farther from the posterior than normal. The internal surface of the uterus was rough. Under a microscope, villi and ends of blood vessels were distinguished with the ends of the blood vessels situated not in the villi but between them; the vessels formed a network, submerging in the coagulated nearly transparent mass, which filled the spaces between the villi. Baer considered this condition to be the beginning of formation of the caducous membrane. How the ovum of mammals and man looks, Baer did not know. "If I knew," he wrote, "that these ova represent opaque small bodies, then I may have found also the ovum, although as far as I searched in the oviduct and in the uterine wall for a vesicle with villi or without them, all efforts were useless" Cp. 8).
Case 2 related to pregnancy which ended due to the mother being scared or frightened in the fourteenth day. The embryonic vesicle was not more than three inches in diameter and covered by delicate villi. From outside, the embryo was not observable. "During the dissection of the ovum," Baer wrote, "I found two slipped combined vesicles: the internal one was smaller than the outer. The rudiment of the embryo was found between them, having the form of an open boat, the length of about 2/3 inch" (p. 9). From the general form of the embryo, it was seen that the back was already formed, and the ventral side was still opened wide. Near the embryo, a cudgel-shaped vesicle, was the allantoic sac. Baer could not find the umbilical vesicle and considered the yolk sac or umbilical vesicle to be the internal vesicle of the embryonic ovum, although it was not clear for him whether it was united with the embryo or not.
Case 3 presented a three-week-old embryo studied by Baer in detail. He described the general view of the embryonic ovum, the chorion, its villi, the connection of the embryo with other parts of the embryonic vesicle (Figure 33, 5), the amnion, umbilical vesicle and allantoic sac (Figure 33, 9) . The embryo and its situation, form and structure are seen in Figure 33, 11. The back of the embryo is closed in all its extension; the occipital protuberance is clear but not strongly protruding. The vesicle of the fourth hillock protrudes significantly and is nearly transparent, since the top of the skull remains very thin there. The lateral fissure is clearly seen, dividing the dorsal and ventral plates. Two convexities are present on the ventral side of the embryo, which Baer at first suggested as the heart and liver, but he then indicated an error, against which he warned other investigators. The anterior projection proved to be the lower jaw, which together with the hypoglossal bone formed from the anterior pair of the branchial arches, protruding more than the others. Behind the projection of the lower jaw, two dark cavities appear. Doubtless these are the branchial slits, which do not yet penetrate the cavity of the pharynx. The posterior projection of the ventral side is the heart, to which a semicanal is affixed, representing the rudiment of the digestive tract, separated during the preparation from the union with the yolk duct; the passage of the abdominal layers into the amnion is also torn. The embryo still has no trace of extremities. The age of the embryo cannot be determined with complete exactness. In any case, Baer assumed it related to a somewhat later stage of development than did the embryo described by Pokel's and was sixteen to twenty days after conception.
Cases 4 and 5 were described briefly due to the unknown length of pregnancy, both approximately three weeks.
Case 6, an embryo three to four weeks old, (Fig* 4 and 6) is described in more detail. The mouth of the embryo was closed, and the branchial slits were not seen, neither from outside nor from the cavity of the pharynx, which was considered an abnormally slow development at this age. The wide stomach, without limits, entered the intestine, while there was an impression that the stalk of the umbilical vesicle was united with the stomach. In the embryo the cord and brain were clearly seen; the ventricle of the heart remained single, but in it the dividing fold had begun to form. In the described case, for the first time in the human embryo, both roots of the aorta could be seen. The lungs were clearly divided into lobes. In the posterior part of the abdominal cavity the urinary bladder was present, extending into the stalk of the allantoic sac. Beside the vertebrae, the posterior halves of primary kidneys were seen.
Case 7, an embryo of five weeks, was very superficially investigated in 1822, because it was obtained in very damaged condition.
Figure 33. Illustration by Baer for the fourth part of UBER ENTWICKLUNGSGESCHICHTE.
5 (Table VI) â€” embryo first month of pregnancy; 9 (Table VI) â€” liberated amnion; 11 (Table VI) â€” embryo, from left side; 4 (Table VII) â€” dog embryo from the side; 6 (Table VII)â€” embryo with dissected abdominal cavity; 22 (Table VII) â€” embryo, from the side; 23 (Table VII)- â€” anterior and posterior extremities of the embryo.
Case 8 was also in the fifth Week of development. The length of the embryo was five inches, well formed. The length of the extremities was about one inch, each extremity consisted of a short stem and a rounded thick end part without traces of fingers. The posterior extremities were much shorter than the anterior, 3 with their end part not separated. Behind the head three pairs of branchial slits were seen, of which the anterior pair was more developed. The branchial slits were very clearly seen from the side of pharyngeal cavity. The degree of development of the lower jaw suggested to Baer that the most interior pair of the branchial slits was already closed. In the spinal cord in the transverse section four strands were distinguished. Half the vertebral arches were not united either among themselves or to the bodies of vertebrae. The auricles were very large in comparison with the ventricles. The latter were still united with each other near the bulb of the aorta. The liver was significantly smaller than the heart, clearly divided into three lobes. The stomach was clearly delineated from the intestine, giving a small bend only in the region of its union with the hollow yolk stalk. After the removal of liver and stomach > the primary kidneys were seen in the cavity of the body along its extension.
Case 9, an embryonic vesicle of five weeks age, Baer obtained in damaged condition. The embryo was destroyed, thus only the embranes could be examined.
In case 10, the embryo was somewhat younger than the previous one, but was slightly more formed than in case 8, as seen in particular in the end parts of the extremities and by the presence of the elbow joint.
Case 11 presented a five-week-old embryonic vesicle (Figure 33, 22-23) with chorion and densely shrunken branched villi. The wall of the chorion consisted of two layers.
3. It must be noted that Baer named them anterior and posterior and not upper and lower extremities, as if he were underlining the identity of man's extremities with the extremities of other vertebrates.
The embryo was very small, although it was well formed. Its head constituted about two-fifths of the total length. The eyes were surrounded by rudiments of eyelids. In the cavity of the pharynx appeared the orifices of the Eustachian tube. The structure of the upper jaw of the embryo shows a similarity to amphibia and tortoises, and the nasal passages of the posterior orifices opened in the most anterior part of the oral cavity. Behind the lower jaw, a pair of branchial slits appeared. Baer considered this a second pair, which remained in all animals for a longer time than the other pairs. In the anterior extremities the shoulder and elbow joints were very clearly seen. The wrist was not separated by a joint from the forearm; it had the form of a rounded blade with five fingers of nearly equal length, except for the noticeably shorter large finger. The spaces between the fingers were narrow, with a semitransparent connecting mass very similar to the swimming membrane. In the posterior extremities the same could be differentiated, but with the fingers less clear. From this Baer could conclude
that the fingers of hands and feet formed not as a result of a simple thickening of the forming mass into separated arms, but because the existing mass collected in these arms, and because the thickness of space between the fingers was less than the thickness of undifferentiated plates. But the most interesting was the similarity of the extremities. The general agreement presented by them was at once striking to the eye. (p. 51)
The liver occupied nearly half of the abdominal cavity. The stomach was well isolated from the intestine, with the form of a blind sac, displaced to the left from the middle plane of the body. Behind the great curvature of the stomach was the spleen. The intestine near the stomach (the duodenum) was slightly curved, which led directly to the place of fixation of the umbilical cord, where the loop forms. The caecum was short, but completely and clearly formed. The left ventricles of the heart in this stage were noticeably larger than the right. The roots of the aorta were only slightly separated from each other. The larynx was barely visible; the rings of trachea were still undifferentiated. The ducts of the primary kidneys opened in the nearly cylindrical allantoic sac. The rudiments of the primary kidneys were shapeless. The relatively differentiated genital organs could not yet be distinguished between ovary or testis. The external genital organ was large, with a fissure at its base where the urinary canal flows.
In case 12, a five-week-old embryonic veiscle with very voluminous amnion, the embryo was invisible. Possibly, here there was a lack of conformity in the degree of development of embryo and its membranes, examples of which Baer had found earlier. For illustration, he presented the following case. A woman who had given birth several times was inclined to spontaneous abortion. At the time of her pregnancy she was subjected to a nervous convulsion, after which she became ill. She was afraid of abortion. Although abortion did not take place, the abdomen from that time increased very little. Forty days before the time of parturition the birth pains began and she gave birth to a fetus very small for the duration of gestation. During the dissection of the fetal ovum, it was found that all ovum membranes were very thick, and the placenta reached in thickness three inches. The embryo itself was flabby, and its size and degree of development corresponded to the age of nine to ten weeks. It was clear that in this case the embryo died after the several mental suffering of the mother, but the membranes continued to develop.
The described observations were accompanied by many general notes. First Baer noticed that only five of the former cases in his illustrations (1, 2, 7, 10 and 12) represented normal features, and the others to some extent were anomalies (especially 4, 5, 6 and 9) . The relation of the dimensions of the embryonic vesicle to the size of embryo varied strongly. For example, in case 5 a relatively large vesicle developed in which the embryo was hardly recognized. There are known cases of detection of embryonic vesicles without embryos which, in Baer's opinion, showed a fixed degree of independence in the development of the embryonic membranes. The embryo can grow sickly and even die, but the life of the membranes is not disturbed; Baer frequently noticed these phenomena in other mammals, in particular in swine in which there are cases of suffocation of certain foeti by thread-like processes from the yolk sac. The embryos during this are underdeveloped, their sizes reaching four to five inches, whereas the embryonic vesicles, while also not reaching the normal size, nonetheless grow to eight inches (20 cm) and more (H 2 ) â€¢ In addition, during normal development in swine the embryonic vesicles in different stages may be of different sizes. From these data it follows that when determining the age of embryos, one must draw attention to the formation of the embryo itself, rather than to the size of the embryonic vesicle.
In concluding notes, Baer considered the structure and development of embryonic membranes. Undoubtedly, his historical interest is represented by the discussions of the most important question at that time, the relation of the pearlike vesicle, given by Pokel the name Erythrois, to the intestine and to the formation of the chorion. Baer considered that the vesicle, which in the human embryo corresponds to the Erythrois of other mammals, is nothing other than the urinary bladder, or since the intestine arises from it, it is considered to be the cloaca.
The formation of the chorion in mammals Baer described as a result of concrescence of the urinary bladder with the outer embryonic membranes and receiving vessels growing near the allantois. Baer was positive that the chorion in man is formed in this manner also. Here he gave a very interesting footnote: "I consider that it is an honor for me," Baer wrote,
that this opinion was repeated by Weber, Frorin and Bischoff . Nearly in the same words they called it a' serious and brilliant hypothesis. In my work, "On the Vascular Connection between Mother and Fetus in Mammals," 4 I suppose, I have shown in detail in different animal forms the gradual formation of the chorion by the union of the urinary sac with the outer membranes of the embryonic ovum. Without drawings, doubt arises because of difficulty in understanding these relationships. Or perhaps it is thought that in dogs, sheep, swine, and rabbits the process occurs in a particular waywhile in humans it occurs differently. Is not man a mammal? Are not the embryonic vesicles in man the same as in other mammals?
4. Baer, "Untersuchungen iiber die Ge fas s verb indgung Zwischen Mutter und Frucht in Saugethieren , " 1828, 305 ff (113).
The same idea of the similarity of development of man with the development of other mammals was mentioned further in the text, when Baer turned to the question about the formation of extremities. "Observations No. 9, 10 and 11 confirm that extremities of man are formed by the same law as in other mammals."
Thus, bearing in mind the report on the subject of the described human embryos and in great part limited to the commentaries of the observed facts, Baer did not avoid giving a conclusion of great significance: that man, as representative of the mammal class, in his structure and embryological development obeys the regularities which are general for all this class.
The concluding section of Baer's major work does not contain theoretical reviews and generalized conclusions. This is not surprising, if we remember the history written at the beginning of this chapter. Circumstances had existed to prevent conclusion of the work, which led to Stieda f s discovery of the papers in unfinished condition after Baer's death. The work of Baer undoubtedly would have been crowned with theoretical conclusions. However, the impatient publisher waited in vain for thirty years of the past century.
Cite this page: Hill, M.A. (2024, March 2) Embryology Book - Russian Embryology (1750 - 1850) 22. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Russian_Embryology_(1750_-_1850)_22
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