ACTIVITIES OF THE OVARY 



71 



by Karl Ernst von Baer (1792-1876). The following statement is taken from 

 de Graaf relative to egg follicles. 



We may assert confidently that eggs are found in all kinds of animals, since 

 they may be observed not only in birds, in fishes, both oviparous and viviparous, 

 but very clearly also in quadrupeds and even in man himself. Since it is known to 

 everyone that eggs are found in birds and fishes, this needs no investigation; but 

 also in rabbits, hares, dogs, swine, sheep, cows, and other animals which we have 

 dissected, those structures similar to vesicles exhibit themselves to the eyes of the 

 dissectors like the germs of eggs in birds. Occurring in the superficial parts of 

 the testicles, they push up the common tunic, and sometimes shine through it, as 

 if their exit from the testis is impending. (See fig. 48; also Corner, '43, page 128.) 



The mammalian egg with a single layer of epithelial cells surrounding it 

 is known as a primary Graafian follicle (fig. 41B-D). As the egg and follicle 

 grow, the number of epithelial cells increase and eventually there are several 



AND 



THECA 

 EXTERNA 

 DEVELOPING EGG 

 THE CUMULUS OOPHORUS 



C. 



Fig. 43. Tertiary conditions of the Graafian follicle in the opossum ovary. Similar con- 

 ditions are found in other mammalian ovaries. (A) Follicle in which the antral vacuoles 

 are beginning to form. (B) This is a follicle in which the antral vacuoles are more 

 numerous and are beginning to coalesce. (C) Condition of the Graafian follicle in the 

 opossum ovary approaching maturity. Observe that the antral space is large and is filled 

 with fluid, the liquor folliculi, while the egg and its surrounding cumulus cells are located 

 at one end of the follicle. The thecal tissue around the follicle is well developed. 



