150 INTERNAL SECRETIONS OF THE OVARY 



results are obtained when an ovary is grafted into a cas- 

 trated male, though where a mature ovary is grafted into a 

 mature male, the periodicity of the ovary is lost and a state 

 which has been compared to persistent oestrus appears. Ham- 

 mond (264) sums up these facts by stating that 'the age of 

 puberty is determined by the nutritive state of the soma of the 

 animal and not by age changes in the ovary itself.' 



Compensatory hypertrophy of the ovary. It has been known 

 for many years that the removal of one ovary will result in the 

 immediate hypertrophy of the remaining ovary. This 

 hypertrophy usually proceeds to a degree which makes possible 

 the maturation of the usual number of follicles (35, 42, 115, 148). 

 It is possible to obtain the same result after removing the whole 

 of one ovary and the greater part of the other. Thus, a small 

 ovarian fragment will undergo extensive hypertrophy and 

 in time produce as many follicles as would both original 

 ovaries. This process of hypertrophy appears to be limited 

 only by the supply of oocytes. Lipschiitz (375) has shown 

 quite definitely that after a time hypertrophied ovarian tissue 

 may become almost denuded of oocytes owing to the com- 

 paratively small number left in the original fragment. This 

 observation is very strong evidence against the view that germ- 

 cells may be re-formed in the adult female. The hypertrophy of 

 ovarian fragments is paralleled by the hypotrophy of super- 

 fluous ovarian tissue. An extra ovary grafted into an animal 

 does not function — three ovaries produce only the same 

 number of mature follicles as do two ovaries. 



The fact that an animal will ripen the normal number of 

 follicles from minute amounts of ovarian tissue shows definitely 

 that some limiting factor is at work to prevent the wholesale 

 maturation of follicles from the normal ovaries. This has been 

 expressed by Lipschiitz (370) as the ' law of follicular constancy.' 

 In the same way the endocrine activity of one ovary becomes as 

 efficient as that of the initial two ovaries. Thus, the length of 

 cycle after unilateral ovariectomy has been shown (425, 491, 

 599) to be indistinguishable from the normal. 



The 'generative ferment.' Heape (288) put forward the 

 hypothesis that some substance required for both growth and 

 reproduction is present in the body in such small amounts 



