Book - Russian Embryology (1750 - 1850) 2
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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 2. Preformation or New Formation?
The clash of the two mutually incompatible points of view on the development of the organism: preformation, or the doctrine of preexistence; and epigenesis, or the doctrine of new formation, can be traced far back in history. Epigenetic opinions had been stated by Aristotle, who knew well from his own observations on the developing chick embryo, that the organs of the latter appear not all at once, but in determined succession. He criticized what came, apparently from the authors of the "Hippocratic collection," who stated that all parts of the embryo appear simultaneously. (8)
Aristotle's ideas possess epigenetic and materialistic contents. However, Aristotle's epigenetic opinions and his materialism, as is known, were inconsistent. His fluctuations between materialism and idealism, about which V. I. Lenin wrote, appear in his opinions about development, and the materialistic idea contradicts his opinion that all epigenesis is an idealistic doctrine. This latter erronerous view also appears throughout the works of the founder of recent epigenesis, K. F. Wolff.
The epigenetic point of view on vertebrate development was also stated distinctly by W Gilliam) Harvey (1651) i n his book "On the Origin of Animals." He, to a significant extent, followed Aristotle. Harvey, like Aristotle, accepted epigenesis for the perfect animals, while the imperfect animals, in his opinion, originated from mold. Harvey differentiated three distinct modes of generation and development of animals : epigenesis, metamorphosis, and spontaneous generation, the last two ways, according to Harvey, inherent in insects.
1. See [Vladimir Ilyich Ulyanov) Lenin, FILOSOFSKIE TETRAD I (Philosophical notebooks) (Gospolitizdat, 1947), pp. 263 - 270.
Harvey's merits are undoubtedly overstated by his British compatriot J(oseph) Needham, who dedicated several enthusiastic pages to him. .Needham was obliged to admit that Harvey "did not break with Aristotelianism, . . . but on the contrary lent his authority to a moribund outlook . . . ."
Harvey's opinions were much more objectively evaluated by an early historian of biology, J. Beseke, in his book published in Russia at the end of the eighteenth century. ^ Beseke noted that "the plastic power" by which Harvey tried to explain Aristotelian epigenesis, in fact did not explain anything, and that Harvey, with his presentation about the three ways of generation, was in fact far from his own principle that "An egg is the common origin of all animals." Proof of this latter general conclusion does not belong to Harvey but to (Francesco) Redi, who proved experimentally that the larvae of meat flies develop not from rotten meat, but from eggs laid by the flies.
In the middle of the seventeenth century the defense of epigenetic opinions, as J. Needham correctly noted, was a step backwards towards Aristotle. It did not require the courage and independence of ideas which proved necessary at the middle of the eighteenth century, when the ideas of preformation became predominant . The emergence of these preformationist ideas began in the second half of the seventeenth century, connected with the oblivion of Descartes' philosophical opinions and Harvey's theoretical propositions. Descartes' biological opinions, mechanical and epigenetic in character, had an acknowledged influence on the development of embryology. His presentations about the embryonic development of animals are stated in the treatise, "Treatise on the Human Body." (9)
2. JCoseph) Needham, A HISTORY OF EMBRYOLOGY, pp. 166 - 167. [Ed.: References are to the German edition, p. 149 of 2nd ed., New York: Abelard-Schuman, 1959.)
3. Jtohann] M(elchior) G(ottlieb) Beseke, VERSUCH EINER GESCHICHTE DER HYPOTHESEN OBER DIE ERZEUGUNG DER THIERE, WIE AUCH EINER GESCHICHTE DES URSPRUNGS DER EINTEILUNG DER NATURKORPER IN DREY RE I CHE. Mitau, Steffenhagen, 1797 (12 unnumbered + 130 pp.) .
Apparently the only great biological theory generated in the seventeenth century was the theory of preformation. According to that theory, the embryonic organism is minute at the earliest period of its existence. (10) One of the earliest defenders of this theory was Marcello Malpighi, who considered that in the egg, in a coagulated condition, there is a completely prepared animal which needs for its unfolding a flow of nutrition.
The preformationists explained that the difficulty or impossibility of seeing parts of the adult creature in the embryo occurs because the organisms are small in number, transparent, and rolled up like balls of thread. The transformation from the apparently uniform homogeneity of the microscopically small embryo to the perceptible polymorphism of the formed organism, i.e. development, was interpreted by the preformists as a thickening of parts and organs, and their development (evolutio) was the untangling of the clew. The etymology of "development" (the origin of this word has been completely lost) undoubtedly finds its origin in preformationist representations.
Malpighi' s preformationist theory was keenly received by his contemporaries. Embryological works and philosophical writings appeared, their conclusions coinciding to a degree with Malpighi 's. The factual data for supporting preformation was achieved by Jan Swammerdam (1637 - 1685); he reached his conclusions from investigation of metamorphosis in insects and some other arthropods. Apparently, Swammerdam was one of the first to revive the idea of generations of embryos enclosed one within the other.
The logical consequence of the preformation theory, the doctrine about "enclosing" of embryos, is not considered a creation of the seventeenth century. Its sources can be traced back to the fourth century of our era.^ The philosophers at the end of the seventeenth century, in particular Malebranche and Leibnitz, interpreted the theory of preformation and the idea of "enclosing." Nicolas de Malebranche, as seen in his main work, "Search for Truth," did not see any improbability in the idea of the eternally great number of embryos wrapped within each other. (11) Malebranche, however, cannot be related to the contemporary preformationists, since he took for granted the changes which originate in the fetus under influences felt by the mother during pregnancy. (12) From Malebranche' s example it can be seen that the doctrine of "enclosing" did not necessarily connect the thinkers of the seventeenth century with the complete theory of preformation, but more often the two were nonetheless connected.
- The Russian word "razvitie" for "development" (also Latin, "evolutio"; German, "Entwicklung"; English and French, "development" and "developpement"; Italian, "svillupo") means unrolling of anything which was originally wrapped up. See A. D. Nekrasov, 0PL0D0TV0RENIE V ZHIVOTNOM TSARSTVE. ISTORIYA PROBLEMY (Fertilization in the animal kingdom. Historical problems), Moscow, 1930, p. 67.
Preformism lies at the base of Leibnitz's opinions. Leibnitz imagined that the existence of the individual substances and bodies of nature proceed from the assumption about the substantial forms or monads, from which is realized the idea of unity of contents and form, material and power, body and soul . The acting powers of nature or monads are primordial and indestructible. From this comes the conclusion that life is also primordial, and therefore there is no basis for supposing that any dead body can become living. Leibnitz decidedly objected to the assumption of spontaneous generation. (13) The impossibility of spontaneous generation and the preexistence of the formed organism nearly led Leibnitz to the idea of the "enclosing." (14) According to Leibnitz, the beginning and the end of the individual do not exist; the origin of the organism consists of extension and development of the preexisting organs, and death is rolling up of the individuality. Leibnitz's understanding of development (evolutio) was not historical (change in time), but rational, i.e. a doctrine about the succession of ideas.
Biology of the eighteenth century adopted Leibnitz's idea, which was equal to his other proposition known as the law of continuity of natural phenomena. The biologistLeibnitzians used the idea of continuity for the foundation of their doctrine of "the chain of being." The internal connection between the idea of preformation and the idea of a continuity of bodies of nature, resulting from Leibnitz's general philosophical conceptions (15), sometimes was kept (Haller, Bonnet) and sometimes was broken. At that time the idea of "the steps" was combined with the epigenetic opinions on development (Radishchev) .
The preformation of the eighteenth century heavily leaned on two trends developed in the previous one hundred years, concerning the bearer of the preformation â€” whether spermatozoid or ovum. The supporters of spermatozoid preformation were called animalculists (from animalculum = animals, which the spermatozoids were called; these were discovered in the seminal fluid by Ham and Leeuwenhoek in 1677) . The supporters of preformation of the embryo in the ovum were named the ovists;" these latter were more numerous and include Haller, Bonnet, Vallisneri and others.
If Vallisneri, as fairly suggested by A. D. Nekrasov, is considered not more than a compiler, Albrecht von Haller and Charles Bonnet were undoubtedly the original investigators. Their theoretical opinions on the development of the organism did not rise, however, above the level of Vallisneri' s presentations.
Haller, who was an early supporter of epigenesis, arrived at the idea of preformation from his own investigations of chick development. (16) These investigations do not give any proof of pre-existence of the organism in the egg, because Haller assumed a close connection of the chicken embryo with the yolk and erroneously took the yolk sac for the yolk membrane. Consolidating the position of preformation, Haller took this doctrine up the hypothesis of "enclosing" (17) and denied the possibility of the new formation in embryonic development. Haller' s aphorisms, "No epigenesis exists" and "No part of the animal appears before the others, and all are simultaneously created," were extremely popular in the second half of the eighteenth century. Haller formulated his discussions more cautiously than Bonnet, and he was willing to discuss the arguments for epigenesis; he positively evaluated wolff's dissertation although he did not agree with his final conclusions.
For details about the animalculists and ovists of the 18th century see the books of A. D. Nekrasov, FERTILIZATION IN THE ANIMAL KINGDOM (1930) and Joseph Needham, HISTORY OF EMBRYOLOGY.
Bonnet was distinguished, on the contrary, by his extreme straightforwardness and his intolerant relations with his theoretical opponents. Bonnet became a supporter of preformation mainly on the basis of his discovery of parthenogenesis in aphids, i.e. the development of their ova without fertilization, and many other observations, in particular of reproduction of the colonial flagellate Volvox. These data, especially about virginal reproduction in aphids Aphis rosae, were taken by the supporters of the theory of "enclosing" as grounds for the triumph of ovists over animalculists. (18)
Bonnet, more decidedly than Haller, defended the hypothesis of "enclosing" and spoke about it as the greatest triumph of reason over sensual perception. Bonnet objected to epigenetic presentations, which judged the moment of organ formation to be when these organs become visible. Bonnet suggested that "inactivity, a state of quiescence, or transparency of some of these parts can make them invisible to us when, in fact, they do exist." 7 To the hypothesis of "enclosing" Bonnet added one more arbitrary assumption, calling for explanation of the phenomena of vegetative reproduction and regeneration: he considered that in animal bodies there are preformed organ rudiments for the restoration of any disturbed unity of the organism.
The idea of "enclosing" was strongly related by the animalculists to spermatozoids, and was related by the ovists to the ova. The fantasy of animalculists was repeatedly ridiculed by the contemporaries, including ovists such as Vallisneri. Greater material for mockery than these fantasies, especially the idea of "enclosing" of countless generations in each other, is reflected by one who was not directly connected with science, but who soberly evaluated the scientific theories of his time. Jonathan Swift's immortal book, which has provided favorite reading for nearly three hundred years of adults and children, satirizes the imaginations of his contemporary microscopists, hinting at the hypothesis of "enclosing" as: Fleas, so naturalists say, Have smaller fleas that on them prey. And these have smaller still to bite 'em, And so proceed ad infinitum.
7. Ch(arles) Bonnet. CONSIDERATIONS SUR LES CORPS ORGANISES (Amsterdam: Chez Marc-Michel Rey, 1762) , part 1 , p . 87 .
Georges Buffon was an inconsistent opponent of the preformation theory. He objected to the theory of "enclosing" and considered that "the organism is something organized in all its parts, developing from an infinite number of similar figures and similar parts into an aggregate of embryos or small embryos or small individuals of its kind." Buffon reached this conclusion by considering the vegetative reproduction of plants and the results of Trembley's experiments on hydra, which showed the possibility of restoring the whole individual from any part of the polyp. Buffon 's assumption about the existence of "living particles," from which complicated organisms are composed, is considered an echo of Leibnitz's doctrine on monads. The embryo, according to Buffon, is built from particles and nutrients which are distributed in it according to some internal form or model ( moule interieur ) . This opinion represents an attempt to reconcile preformation (presence of a preexisting internal model) with epigenesis (gradual formation of the developing organism from the nutrients received from without) .
Buffon' s opinions were widely known to readers because of the great popularity of his works , which were written in lively and picturesque language. Because of their inconsistencies, however, Buffon 's opinions did not show the essential clash between the ideas of preformation and epigenesis. The theory of preformation along with the hypothesis of "enclosing" of the embryos remained predominant to the end of the eighteenth century, despite K. F. Wolff's works which had already struck a shattering blow.
8. (Ed.: "On Poetry" (1733) . Actually a well-known ditty by Jonathan Swift . J
9. Pushkin called Buffon "the great pictorialist of nature." "The style of his blooming always will be an example of descriptive prose" (A. S. Pushkin, POLNOE SOB RAN IE SOCHINENII (Complete collected works) in 6 volumes, (Moscow, 1936), v. VI, p. 24).
Cite this page: Hill, M.A. (2020, October 26) Embryology Book - Russian Embryology (1750 - 1850) 2. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Russian_Embryology_(1750_-_1850)_2
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