OVARIES. 245 



structure of these, but the corpora lutea vera, in consequence 

 of the marked hypersemia of the ovary during pregnancy, are 

 larger. The corpora lutea vera as well as the corpora albicantia 

 resulting from them remain longer in the ovary, because their 

 retrogression is slower than in the corpora lutea spuria. 



FIG. 186. 





Lutein cells 



'^^_^^ Connective- 

 i J^? tissue septa 



, /Blood-vessel 



- 



^^ ^ %r^~" 



--* " * -*-t ' 



Part of a corpus luteum of a bitch. X 300. 



It is to be noted that only a small proportion of the ova 

 in the ovary become ripe. According to Henle, of about 

 72,000 ova in the ovaries of one individual, only 400 arrive at 

 maturity. The rest undergo degenerative changes which 

 represent an entirely physiological process, known asfollicular 

 atresia. This depends on a series of changes not only in the 

 organ itself, but also in the follicular epithelium and the theca. 



