194 



PHYSIOLOGY OF FARM ANIMALS 



[CH, 



the external characters of the sex is hoAvever very obscure, and m 

 mammals removal of the ovaries does not lead to the development 

 of male characters (e.g. in Herdwick sheeji which are horned in 

 the male but hornless in the female, ovariotomy or extirpation 

 of the ovaries does not lead to horn development). 



That the ovaries are responsible for the oestrous cycle is 



i^^. 



Fig. 102. Transverse section through 

 uterus of rat, six months after 

 ovariotomy, showing degenerative 

 changes (from Marshall). 



certain, for ovariotomy is followed by atrophy of the uterus and 

 heat no longer recurs. That the ovarian influence is chemical 

 rather than nervous is proved by the fact that successful trans- 

 plantation of the ovaries to an abnormal position, such as on to 

 the ventral wall of the body cavity or into the tissue of the kidney, 

 is sufficient to admit of the recurrence of the cj^cle and the normal 

 maintenance of the uterine nutrition in spite of the ordinary nerve 

 connections of the ovaries having been severed. The grafted 



