146 INTERNAL SECRETIONS OF THE OVARY 



to the so-called interstitial tissue of the ovary suggests a com- 

 parison with the supposed endocrine activity of this latter tissue. 

 On the other hand, the irregularity of the occurrence of ovarian 

 interstitial tissue, together with our complete ignorance as to 

 its endocrine significance, makes it difficult to arrive at any 

 conclusions. 



Significance of occurrence of cestrus after follicular ablation. 

 Allen (12) has doubted whether any real information regarding 

 the normal animal can be obtained from these experiments on 

 sterilized mice. This objection might be of importance if the 

 sterilized mouse were separate and distinct from the norrral 

 animal. In animals irradiated when adult, however, the 

 change to the sterilized condition is very gradual. Even after 

 a dose of X-rays which will lead to complete sterility, the 

 degeneration of the follicles is comparatively slow, and during 

 the transition period when the Graafian follicles are gradually 

 disappearing, the oestrous cycle shows no abnormality. Since 

 it is unlikely that the regulation of oestrous periodicity could 

 be taken over imperceptibly by a different mechanism while the 

 sterilization changes are proceeding, it is highly probable that 

 the same periodic mechanism is at work in the sterilized animal 

 as in the normal. Three general conclusions may be drawn from 

 these experiments on the occurrence of the oestrous cycle after 

 X-ray sterilization: 



(a) The Graafian follicle is probably not the essential source of 

 the oestrus-producing hormone; 



[h) The periodicity of oestrus is not governed by the periodic 

 maturation of follicles; 



(c) Since the elimination of the corpora lutea of ovulation has 

 also no effect on the periodicity of oestrus, they can 

 perform no such inhibitory function in the unmated 

 mouse as has been demonstrated by Hammond (265) in 

 the cow and by Loeb (390, 400) in the guinea-pig. 



In those animals in which the corpora lutea of ovulation have 

 been shown to inhibit the next oestrous period, it is probable 

 that the elimination of the follicular system would, by indirectly 

 eliminating the corpora lutea, shorten the dioestrous interval. 

 The same result would be expected in the mouse under condi- 



