Editing William Harvey (section)

== ''On Animal Generation'' ==
Harvey's other major work was ''Exercitationes de generatione animalium'' (''On Animal Generation''), published in 1651. He had been working on it for many years but might never have finished it without the encouragement of his friend [[George Ent]].<ref name="ODNB">{{cite ODNB |id=12531 |title=William Harvey |first=Roger |last=French |author-link=Roger Kenneth French |url=http://www.oxforddnb.com/view/article/12531 |access-date=1 January 2014|freearticle=yes}}</ref>

The book starts with a description of the development of the hen's egg. The major part is theoretical, dealing with [[Aristotle]]'s theories and the work of the physicians following [[Galen]] and up to Fabricius. Finally, he deals with [[embryogenesis]] in [[viviparous]] animals, especially hinds and does. The treatment is generally Aristotelian and limited by use of a simple magnifying lens.

[[Joseph Needham|Needham]] claims the following achievements for this work.<ref>{{cite book |title=A History of Embryology. |last=Needham |first=Joseph |pages=133–153 |year=1934 |url=http://babel.hathitrust.org/cgi/pt?id=mdp.39015036683129;view=1up;seq=157|publisher=New York }}</ref>
*His doctrine of ''omne vivum ex ovo'' (all life comes from the egg) was the first definite statement against the idea of [[spontaneous generation]]. He denied the possibility of generation from excrement and from mud, and pointed out that even worms have eggs.
*He identified the citricula as the point in the yolk from which the embryo develops and the [[blastoderm]] surrounding the embryo.
*He dismantled once and for all the Aristotelian (semen-blood) and Epicurean (semen-semen) theories of early embryogeny.
*He settled the long controversy about which parts of the egg were nutritive and which were formative, by demonstrating the unreality of the distinction.{{citation needed|date=January 2019}}