THE PERIODICITY OF OESTRUS 



141 



of the usual type of ovary resulting from sterilization before 

 puberty. Subsequently, a second proliferation from the germinal 

 epithelium may take place in the form of cords resembling 

 small anovular follicles or embryonic testis tubules. The weight 

 of evidence favours the view that they are of the former nature. 

 In certain abnormal mice the first proliferation from the 

 germinal epithelium becomes extremely luteal-like, and, since 

 this tissue forms almost the whole of the sterilized ovarv, the 



J" ' 



>- ^^ 









- - t 



"V;-- 









Fig. 47. — Ovary of Mouse sterilized by Exposure to 



x-rays when adult. 



The ovary is largely composed of tissue derived from the old follicles. 



appearance of a single large corpus luteum is produced. This 

 abnormal type of sterilized ovary results more commonly from 

 sterilization immediately after birth than at three weeks old. 

 iVnimals with the abnormal type of sterilized ovary show 

 physiological abnormalities, including inhibition of oestrus. 



Sterilization of the adult mouse leads roughly to the same 

 kind of histological change, but the details are somewhat 

 different. In the irradiated adult, the elements already forming 

 the ovarian cortex at the time of irradiation persist in a changed 



