CHAPTER 15 



BAER'S TREATISE DE OVI MAMMALIUM ET HOMINIS GENESI 1 



From the time of Hippocrates and Aristotle to the 

 seventeenth century, the idea predominated that the source 

 for development of a new individual is some "generative 

 material" which is present in the female sexual organs. It 

 was considered analogous to the male sperm and was frequently 

 called the female sperm. By extension, the ovaries were named 

 the "female testicles." Following Harvey's statement that 

 "all that is living comes from the ovum," the idea that the 

 source of development for all animals, including mammals, is 

 the ovum, received a wide distribution. Johann van Horn and 

 Nicholas Stensen claimed that the ova of mammals are those 

 early-opened follicles of the ovary. They contended that the 

 ova (follicles) represent generative material for future 

 generations, an idea supported in particular by the anatomist 

 Ruysch. In accordance with the new point of view, the female 

 sexual gland was named the ovary. 



In 1672 (Rene) de Graaf played a very important role with 

 his detailed study of the structure of the ovary. He actually 

 discovered the ovarian cycle, i.e. the interrelation between 

 the follicle and the corpus luteum. De Graaf thought that the 

 ovum exists below the membranes of the mature follicle 

 (Graafian vesicle) ; however, the nature of the latter remained 

 unknown to him. From his investigations, de Graaf concluded 

 that: "All animals in general, and in the same respect man 

 himself, get their beginning from the ovum which is present 

 (in the female testicles) prior to copulation." This statement 

 formed the anatomical basis of Harvey's thesis, and at the 

 same time was in agreement with predominating earlier ideas. 



1. (Ed.-. Baer, DE OVI MAMMALIUM ET HOMINIS GENESI 



(Leipzig, 1827) ; translated by Charles Donald O'Malley, 

 ON THE GENESIS OF THE OVUM OF MAMMALS AND OF MAN 

 (Cambridge, Mass.: History of Science Society, 1956).) 



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