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c h a p t e r e i g h t Generation and the Formation of the Chick in the Egg 8.1 Generation and Its Problems The problem of generation is one of the most demanding—both technically and conceptually —in the entire history of anatomy and over the centuries had attracted the attention of anatomists, philosophers, and historians. Besides the structure of female and male reproductive organs in different animals, several issues are at stake, such as the respective role of female and male parents and the order of formation of the organs in the fetus. The identification of the stages of the formation of the fetus had profound implications on the understanding of the organism: Aristotle, for example, saw the heart as the primary organ and believed that it was formed first, whereas in some writings Galen argued for the priority of the liver over the heart.¹ Since antiquity, the formation of the chick in the egg had been chosen as a particularly convenient and affordable case for the study of generation, with the chick as a “model organism”: the authors of the Hippocratic corpus and Aristotle wrote on it, and so did in modern times the Dutch anatomist and physician Volcher Coiter and his Bologna teacher Ulisse Aldrovandi, as well as Hieronymus Fabricius and his pupil Harvey. Although the formation of the chick in the egg is but a subsection of the problem of generation, this itself is not easily manageable: Howard Adelmann’s monumental study of Malpighi’s contributions is accompanied by twenty-six excursuses exceeding one thousand folio pages. Adelmann’s work is an indispensable tool, yet despite his remarkable technical competence and historical erudition, in this huge amount of material it is often hard to tell the forest from the trees, to characterize the contributions of individual anatomists whose work is presented fragmentarily, and to identify broader themes and problems.² The aim of this chapter is to identify in this vast and at times rugged landscape some key themes and problems associated with generation. Section 8.2 is devoted to William Harvey’s 1651 De generatione animalium. The problem of generation was a natural area of research for an Aristotelian anatomist and a student of Fabricius; fol- Generation and the Formation of the Chick in the Egg 209 lowing Aristotle and Fabricius, Harvey studied extensively the generation process of the chick in the egg and of deer, as representative of viviparous animals. I shall discuss the former topic, focusing on the interplay between epigenesis—a term he coined, meaning the formation of the fetus gradually or part after part—and preformation, or the belief that the parts of the animal are preformed and no differentiation occurs but only growth.³ Harvey’s claims about epigenesis and the soul with its faculties, such as the formative faculty or plastic power, were to come under attack by mechanistic anatomists, who found generation especially challenging. By way of contrast, I sketch in a few words the mechanistic explanation adopted by Descartes, who rejected the belief that generation is a faculty of the soul. Section 8.3 investigates changing views on the structure of male and female organs of reproduction and the mystery of conception . The main period I examine corresponds quite closely to that of the previous chapter, from the late 1660s to the early 1670s; indeed, while Redi was investigating the generation of insects in Steno’s company, Steno was reaching profound results about the structure of female organs of generation and generation as a whole, with his identification of the so-called female testicles as ovaries. Meanwhile, Reinier de Graaf published treatises on the male and female organs of reproduction in which he expanded on Steno’s research. De Graaf did not live to witness the discovery of spermatozoa, whose 1677 announcement to the Royal Society by van Leeuwenhoek was received with skepticism. Section 8.4 discusses the work on generation by Swammerdam and a group of Amsterdam anatomists, with special emphasis on the philosophical and also theological implications of preformation. With his belief in the encapsulation of all subsequent generations in the first egg, Swammerdam brought preformation to its most extreme version; his and Harvey’s views occupy opposite positions with respect to epigenesis and preformation. I also discuss a later correspondence in which Malpighi criticized Swammerdam’s positions. In 1673 and 1675 the Royal Society published two works by Malpighi on the formation of the chick in...

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