Book - Russian Embryology (1750 - 1850) 6
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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 6. Wolff's Teratological Works
On publishing the work discussed above about the development of the intestine, for which the main objective was to establish the theory of epigenesis, Wolff never considered his task accomplished. He always sought new material for the question in which he was interested.
The actual arguments against preformation and in favor of epigenesis he drew from teratology, which he continued studying extensively throughout his long years of work in Petersburg. From Raikov's work it is clear that Wolff had collected a large amount of material in which he investigated in detail the structure of human monsters or malformations, which, along with his theoretical judgments concerning a number of general biological problems, were never prepared for publication.
In addition to human monstrosities, Wolff was interested in the development of animal monstrosities, as evidenced by his three publications on the subject. Two of them, "About chicken monstrosities" and "Description of a double-headed chicken," are included in the list of Wolff's printed works attached to Raikov's book, although their inclusion in this book is not highlighted, and a third, "A single egg carrying twins," is not included in the list. These works of Wolff, in Latin, remain almost unknown. Thus it becomes essential to give a short account of their contents; moreover, interesting factual data is in all of these works, and to the second, the most commonly known, is attached on independent report, "About the origin of monsters."
1. Wolff, "Ovum simplex gemelliferum, " NOVI COMMENT. ACAD. SCIENT. PETROPOLIT. v. XIV pro Anno MDCCLXIX, 1770, pp. 456 - 483.
Wolff's first published teratological work, his "A single egg carrying twins^ (Fig. 8 - 10), begins with the reminder that eggs bearing twins were known by Harvey and Fabricius Aquapendente and even Aristotle. However, all these authors worked not with single eggs which contain one simple yolk with two embryos developing in it, but with eggs containing two yolks, each of which gives rise to a separate embryo. Wolff wrote that he also saw many eggs with double yolks; he suggested naming them the twin-eggs in distinction from the single eggs carrying twins (p. 457). He considered the methods of development of this and other types of eggs. For the formation of twin eggs it is necessary that two yolks be separated in the ovary and be passed separately along the oviduct, after which in the lower part of the oviduct they are surrounded by a common white mass and covered with a common shell. Two yolks in one egg could be closely adjacent to each other; however, they remain separated and represent at the end two different eggs in one shell. Something else completely is represented by the egg carrying twins, which contains a single and is actually single in every sense. Such an egg is single throughout its entire existence but nevertheless produces two embryos.
The egg described in this work, which carried twins, was incubated for six days. Wolff gave a short description of the situation of the parts in a normal egg. At this time of incubation the albumin is separated from the yolk and is located at the pointed end of the egg. The vascular zone (area vasculosa) occupies half of the surface of the yolk and is supplied with rare vascular branches. The transparent zone (area pellucida) , which represents the central part of the vascular zone, i.e. the place where the embryo is located, disappears by the sixth day of incubation in normal eggs.
In the egg carrying twins, the albumin is single and common for both embryos and normal in size and location. The yolk also is single and does not show anything abnormal (p. 465). The vascular zone is also single; however, the vessels present in it form a double system of branching which is considered the first sign of doubling of the embryo. The strange property of this egg is the absence of the amnion; thus both embryos look entirely unusual: they are free, covered with nothing, and lie movable on the yolk (p. 469). Skin of the abdomen in both embryos gets across in the membrane of the yolk, as a result of which there are independent yolk ducts for each embryo. The latter lie so close to each other that a third one cannot be situated between them; their head ends are especially close.
Later, Wolff described the folds on the surface of the yolk between the embryo and the openings of their intestines into the yolk. In the structure of the embryos themselves he did not notice anything deviating from the normal.
In a special section of the work (Corollaria quaedam) Wolff turned particular attention to the folds of the yolk membranes, which are located between the embryos, He believed these to be the remnants of the false amnion, which from the first to the fifth day was present there. Therefore his opinion was that the false amnion and area pellucida were common for both embryos at the preceding stages. Comparing the described case with examples of joined twins in the literature, Wolff expressed his belief that the growing twins do not result from the growth of the already formed embryos, admitting at the same time that they are a product of incomplete division of the embryo at the early stage.
In the work Wolff reached no general conclusions. However the distinction of the egg with two yolks, where the presence of two embryos is entirely natural, from the twins originating from one yolk is very obvious. Wolff undoubtedly wanted to demonstrate a phenomenon which supported the theory of epigenesis. The presence of two embryos connected with one yolk indicates that the preformation of a ready embryo in the egg does not exist and that the development occurs of epigenesis .
Wolff's second teratological work again is concerned with the disturbance in the development of the chicken embryo. 2 This is a small note with the following content. In the spring of 1777, some of the eggs under a sitting hen did not hatch chickens. On opening such eggs, it was revealed that they either were sterile or they contained dead embryos. From one of these eggs Wolff extracted a monster chicken, which provided the subject of the following description (Tig s Â« 11 - 12). The chicken looked completely ready for hatching. It had a single head, neck, thorax and abdomen, but the extremities were four pairs in number: two pairs of legs and wings. The situation of the extremities was such that it was easy to distinguish the natural from the additional The additional legs were attached to the thighs at the sacral region and directed to the head end of the chicken, i.e. in a situation opposite the natural legs. The origins of the additional wings were located backwards from the origin of the additional legs in the coccyx region. The impression is that the additional wings and legs belong to another undeveloped chicken, which is located on the original chicken. The underdeveloped chicken is positioned as if the head and neck of the first are hidden in the pubic region of the formed partner, and the chest and abdomen are embedded in the sacral region of the latter, so that externally only the legs and wings appear.
2. Wolff, "De pullo monstroso, quatuor pedibus, totidemque alis instructo, ACTA ACAD. SCIENT. PETROPOLITANAE , 1783/ PP. 203 - 207.
On opening it, Wolff found that the abdominal protuberance contained a single yolk. In the structure of the internal organs of the primary chicken, no deviations from normal were seen with the exception that instead of the two blind outgrowths of the intestine there were three. All of the internal organs related to the primary chicken, and in the second there was nothing except the extremities â€” neither neck, nor head, nor abdomen, nor thorax nor an internal cavity.
The article is terminated by a quick comparison with the monsters described in literature and does not contain any general conclusions. This is entirely natural, because earlier Wolff had published another teratological work about the double-headed calf, which was accompanied with a theoretical chapter containing conclusions related to the above-described monstrosity. The material described in the last mentioned work is a calf which died at birth. It had two heads and two necks, but a single chest, abdomen and a normal number of extremities.
3. Wolff, "Descriptio vituli bicipitis cui accedit commentatio de ortu monstrorum," NOVI COMMENT. ACAD. SCI. PETROP., XVII, 1773, pp. 540 - 573.
The vertebral column was duplicated at the level of the second-third thoracic vertebrae; from here anteriorly it extended in duplicate, and posteriorly; a single vertebra extended. As a whole, the calf was somewhat deformed, the thorax and back were humped, the posterior legs were deformed,
On opening, one heart was found, three lungs and two trachea, and the corresponding presence of two heads with a change in the number and location of the blood vessels (Figure 13). The latter are described in detail with Wolff's usual accuracy. This description can be bypassed in order to come to the main part of the given subject, the article "On the Origin of Monsters."
First of all, Wolff compared two points of view about the origin of twin monsters. One considered the possibility of accidental collision and union of previously separated embryos. "The famous Haller and (Jacques Benigne) Winslow, who are equally great persons," Wolff wrote, have turned the arguments against this hypothesis . . They noticed in the monsters accuracy and regularity of the structure, not less than in the normal, which could not occur in case of accidental collision and union, or in case of accidental transmutation. This regularity is recognized in our monsters as well as in many others . Why does the esophagus of one calf join with the esophagus of another calf, and not with any other part; why do they accrete with each other? Why does the lung of one accrete with the lung of another; why is the anonymous artery in the same manner attached to the anonymous artery or to the aorta of another and is accreted with it? Why, in any of the monsters, does the esophagus not accrete with the jugular vein, the lung with the liver, the carotid artery with the hollow vein? Could parts of one fetus instinctively find tl e corresponding parts of another? (p. 550)
Figures 8-10. Illustrations of Wolff's work "Single egg carrying twins."
8. Egg extracted from the shell; a - albumin; b- yolk;
c - the part of the terminal vein; d - the part of the yolk which is devoid of vessels; e - area vasculosa; f , g- - upper and lower embryo; h - the part of the umbilical vesicle of the upper embryo; i - a depression in the yolk which is produced by this vesicle; k, m - umbilical vesicle of the upper and lower embryos; n, o - folds of the yolk membrane; P/ <lr r - yolk vessels of the upper embryo; t, u, v- the same vessels of the lower embryo .
9. The part of the membrane adjacent to the embryo, from the internal aspects; a - border of the cut membranes; b, c - upper and lower embryos ; d , e - folds of the membranes ;
f, o - openings of the intestinal canal of the upper and lower embryos; p, q - border of the abdominal umbilical opening which is transparent throughout the membranes; h, i, k, m, n- - yolk vessels of the upper embryo; r - same vessels of the lower embryo.
10. Internal surface of the external membranes which is seen after being separated and turned internally; a - external yolk membrane; b, c - lower and upper embryos; d, e - part of the internal membrane which extends into the intestines of both embryos; f, g - their umbilical bladders; h - opening of the umbilicus through which the internal yolk membrane, which is a continuation of the intestine, leads out from the abdomen; k- vessels; 1, m - folds of the membranes .
Figures 11 - 12. Illustration for Wolff's "On the monstrous chicken" (11 External view of the chicken? 12 Viscera).
Wolff came to the conclusion that it is impossible to explain the given condition as the union of two embryos. As a result of that, he raised another question: could it be possible that the monsters originate from embryos which are created monstrously and are prompted to develop like the normal, but which by the powers of nature grow incorrectly? "None of the famous authors writing about monsters," Wolff said, "discuss this question, but rejecting the hypothesis of collision and accidental transmutation, they all now talk about embryos which are created monstrously, as if it is necessary that they begin from predestined embryos" (p. 553).
Thus Wolff formulated the solution of the question, "How do monsters developâ€” under the effect of the modified powers of nature causing the development, or are their embryos directly created by God and only changed by the powers of nature?" (PP- 553 - 554).
First of all he rejected the accidental development of monsters, because in their structure it is possible to recognize features of beauty, regularity and expediency. From another aspect, monsters occur so faultily organized, so imperfect, that it is impossible to believe that this was created directly by the action of God. As an illustration Wolff gives the case of the duplicated monstrosity which was described by Wins low, where the union of two babies in the pelvic region led to such impairment of the urogenital system of one of the partners that the seminal ducts opened in the urinary bladder. Wolff concluded that: "The rudiments of such deviations from natural structures are to a great extent imperfect, and hence are deserving of deep sorrow from people. They could not have been created and predetermined." (p. 556)
Wolff was not satisfied with this example and gave others; each additional example should increasingly confirm the opinion he held. For example, he referred to the human fetus described by CJean de) Mery in 1700 in which the region of the lumbar vertebrae was twisted in such a way that its knees and feet were directed backwards. The skull cavity, thorax and stomach were opened, the auricles joined in one cavity receiving in itself all the veins, and so on. On the basis of that and some other monsters he mentioned which were still more imperfect, Wolff stated: "I consider it is impossible that any individual animal species of this type could have been logically thought to exist in such a way that the species could not possibly live," Q>. 560) Further on, Wolff gave the case of the sheep embryo monstrosity described by Antonelli in 1703, which consisted of an abdomen with an umbilicus and hind legs, but without head, anterior legs and thoracic cavity; in the abdominal cavity there was nothing except a mesentry with the intestine and a deformed stomach, i.e. there was neither a liver, nor a kidney and moreover no heart and lungs.
The monster described by Barfolome Zeifart, in addition to its other imperfections, was characterized by the presence of one well -formed eye at the base of the forehead, which was at the same time devoid of the optic nerve, "What is the purpose of such an eye," Wolff asked. "If it could see, why was there not an optic nerve? If it could not see, why, in this monster, was such an incomplete eye formed?" The general conclusion Wolff reached is stated in the following sentences: "I am sure that these examples are sufficient for proving that monsters are not the production of God, but of nature; however, there are productions which have developed unsuccessfully." Cp- 567) The report is terminated by short statements showing the importance of studying monsters in order to establish the historical theory of development, i.e. for the substantiation of epigenesis.
Not in any other single report did Wolff mention God so frequently and constantly as in this work, where he names Him as the High Power, sometimes as the High Creator, or as the very wise Founder, or as the Essence of intelligence. All these names were set up in capital letters and were sharply pronounced throughout the text. The work is produced in such a way as to create the impression that it is theological in origin. Actually it was evaluated as such by observers in the period of Queen Catherine II when the latter actively pursued the representatives of progressive thought in Russia.
Wolff's argument itself does not look usual here. In the letter of Wolff to Haller, 4 written in answer to Haller's preference for preformation over epigenesis, which is in agreement with religious presentations, the subtle ironyconcerning such arguments sounds bad. And in the work just described, "About the origin of monsters," as if referring to an argument of the same nature, Wolff referred relating the intentional creation of these monsters to God as doubting His wisdom. It is sufficient, however, to consider all those "devout" sentences of Wolff to realize that his main task was to eliminate God from nature. He makes that goal applicable mainly to the development of monsters, but he also relates these discussions to normal development. The results are in complete agreement with his observations in other works, in which he frequently stressed the relationship of the processes of development to natural true reasons.
4. The translation of this letter is given in B. E. Raikov's book, pp. 67-78.
Besides the above-mentioned teratological works, Wolff published also a small work "Note, concerning the double monsters, whose two bodies are connected by the posterior parts. "5 in this note, Wolff related that on May 21, 1778 Senat notified the Academy about the birth of a live double monster by a woman in the province of Tversk. The accreted twins lived for two months and were then given to the Academy. They were united at the posterior surface of the pelvic region from the upper edge to the coccyx; the posterior secretory opening was general for both. The remaining parts of the trunk, heads and extremities were entirely separated. The note is terminated by the statement that detailed description of this monster would be published later. Apparently Wolff meant to include the description of this case in a large teratological monograph, but that work was interrupted by his death. Wolff's drawing, which is published by A. E. Gaisinovich from the archive of the Academy of Science of USSR and which is reproduced here CFig. 14), undoubtedly illustrates the case described. 6
5. Wolff, "Notice touchant un monstre biforme, dont les deux corps sont reunis par derriere," ACTA ACAD. SCIENT. PETROPOL. pro anno 1770, part 1, 1780, pp. 41 - 44.
6. A. E. Gaisinovich, "K. F. Wolff and the study of development," in K. F. WOLFF: THEORY OF CONCEPTION
(Academy of Science USSR, 1950) . The mentioned drawing is located between pp. 472 and 473.
Figure 13. Illustration to Wolff's "Description of double-headed calf."
Figure 14. Illustration of Wolff, showing accreted twins.
In regard to opinions concerning monstrosities as a result of sharp deviations from normal development, there are Wolff's judgments about the variable features in general, which are observed in particular in human anatomy The latter was elucidated by Wolff's special work, "About the instability of the structure of the human body and about the examples selected for the demonstration of this instability." The article contains numerous examples of anatomical variations in man. Wolff noted that not only small venous branches whose variability is endless and is not defined, not only large veins and arterial vessels, not only nerves, but also bones, muscles and the internal organs are characterized by instability. This is related, according to Wolff, even to the "most precious parts of the body as the heart and brain to the extent that it is hardly possible to find even two human bodies in which these precious internal organs are identical in their form, situation and proportions" (p. 217 - 218], The variability of organs in the adults depends on their more distinctly expressed variability in the embryonic period. For the illustration he referred to the fact of the deep differences in the structure of the chick embryos, which "are sometimes so unequal that they could have been mistaken as other animals if it was not known that they had been taken from chicken eggs" (p. 223).
Wolff's epigenetic ideas, which he based on study of ontogenetic development and on variability in individual development, should certainly have led Wolff to question the origin of diversity of organic forms, i.e. to the problem of evolution in the modern understanding of this word. Actually, if development is a new-formation and not growth from the beginning of existence; the variability of creatures could not be primordial, could not be a sequence of a creative action. In the published reports Wolff did not consider this question himself; however, the significance of the principle of epigenesis did not escape Engels' insight into the problems of species evolution. In DIALECTICS OF NATURE the following very significant paragraphs were dedicated to Wolff: "... K. Wolff produced in 1759 the first attack on the theory of the stability of the types as species, proclaiming the study of their development."**
7. Wolff, "De inconstantia fabricae corporis humani ,
de eligendisque ad earn representandum exemplaribus , " ACTA ACAD. SCIENT. PETROP . pro anno 1778 (1781), pp. 217 - 235. The judgment about this subject can also be found in others of Wolff's anatomical works (see list in Wolffs THEORY OF CONCEPTION, Academy of Science USSR, 1950, pp. 478 - 480).
An identical opinion about the significance of Wolff's investigations was stated by Ya. A. Barzenkov in a posthumously published outline of the history of comparative anatomy. ^ On characterizing the theory of "evolution" of Haller and Bonnet and the study connected with it about "inserting of the embryos," Barzenkov wrote: "From this theory, by the way, one sequence developed which is very important for the theoretical natural sciences: the stability, and the invariability of the types." (p. 96) "As a very young man, Wolff ... came to the belief that this theory is not possible." (p. 97) Proving the falseness of preformation and turning instead to the principle of epigenesis, Wolff consequently disproved also the idea of the stability of types. The quotations from Wolff's manuscripts which were recently published by B. E. Raikov undoubtedly indicate that he was sure of the support for the changeability of the types and, therefore, can be truly considered one of the predecessors of Lamarck and Darwin.
Giving credit to Wolff's efforts to proving epigenesis, his idea about the origin of the parts of the embryo from folds having the form of plates or leaves must be noted in particular, because this observation influenced Pander and Baer.
The previously discussed list of Wolff's works undoubtedly indicates that he actually had seen these structures and called them leaves or membranes. It is possible also to give another example, from which it can be concluded that he had seen not only layers in the embryo itself, but that he also recognized that by their means the embryo and all the remaining blastodisc are united into a single unity. Describing the structure of the "cardiac fossa" which represents, according to Wolff's description, the fold of the stomach, he noted that the "membrane constituting the substance of the stomach does not break down at the border of the fossa , and leads into the internal layer of the transparent part of the vascular area and then into the internal layer of the yolk itself."
8. F. Engels, Old introduction to DIALECTICS OF MATURE (STAROE VVEDENIE K DIALEKTIKE PRIRODY) , K. MARX AND F. ENGELS. SOCH., v. xiv, p. 483.
9. Readings of Ya. A. Barzenkov about comparative anatomy. Uch. Zap. Mosk. un-ta, vyp. 4, 1884, p. 242.
There is no doubt that this observation should have been discussed as showing the continuity of the layers of the embryonic and extra- embryonic entoderm which is connected with the visceral layer of the mesoderm. Wolff saw the embryonic layers, but he did not understand their significance. The theory of the embryonic layers represents the product of the first half of the nineteenth century and is connected with the names of the Russian acadamicians Pander and Baer. Wolff only established the factual basis on which this theory could be later constructed.
10. DE FORMATIONE INTESTINORUM, p. 454
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