explored by looking at it under the microscope, and Baer 

 described it alive subsequently in his autobiography. Here, 

 he only talked about how he was surprised at seeing the ovum 

 in the ovary, which he already had observed in the ducts 

 "so clearly that it can be seen by a blind man" (p. 12). 

 The ovule had a diameter of one-thirtieth to one-twentieth 

 of a Parisian line. On the surface of the ovule, there is 

 a ring-shaped plate, which Baer called the discus pvoligevus. 



In § 4, "How the Graafian Vesicles are Constructed and 

 General Considerations on the Mammalian Ovule," Baer stated 

 that, besides the ovaries of dogs, he had investigated the 

 ovaries of cows, pigs, sheep, rabbits, hedgehogs, dolphins, 

 and man. He was convinced that in all the mammals studied > 

 the Graafian vesicles have an identical structure. Each 

 Graafian vesicle has two parts — an enveloping part, or the 

 shell (putamen) , and the part included inside its nucleus. 

 The first is composed of membranes, not related to the 

 Graafian vesicle but to the ovary, and only a little raised 

 by the follicle. 



The membrane (indusium) covers only part of the follicle; 

 it is composed of peritoneal epithelium (Figure 26, IX, 1) 

 and of what is called cellular tissue, termed by some authors 

 albuginea. This theca consists of two layers, an external 

 and an internal layer. The external is thin and transparent, 

 composed of compact cellular tissue. It receives the blood 

 vessels and sends their terminal branches into the next layer. 

 The internal layer is thicker, softer and darker; its internal 

 surface is covered with delicate fibers. The external surface 

 is firmly connected with the external layer. In the place of 

 the future rupture, a thinning of the theca occurs as a 

 transparent spot. 



Related to the nucleus are the following: granular 

 membrane, follicle fluid, embryonic disk, and the ovule itself. 

 The granular membrane is composed of a thin layer of granules 

 and includes the fluid content of the Graafian vesicles. The 

 humor consists of fluid and granules swimming in it. In 

 natural follicles, the fluid is yellow-colored, perhaps because 

 of the yellow color of the granules. Boiling the fluid and 

 the effect of alcohol cause the fluid to coagulate, which 

 indicates its protein nature. The embryonic disk and the 

 cumulus are in the fluid or on its surface. They consist of 



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