170 INTERNAL SECRETIONS OF THE OVARY 



suitable dosage ovulation might be induced without terminating 

 gestation. It is possible that ovulation may be caused by 

 amounts of anterior pituitary insufficient to produce enough 

 oestrin to cause abortion. The abortion induced by anterior 

 pituitary implants is clearly comparable with that produced 

 by oestrin injection (see p. ii8). 



The senile animal. Zondek and Aschheim (658) have reported 

 that oestrus can be induced in the senile mouse after the 

 cessation of the cycle by anterior pituitary treatment. In this 

 case the result differs essentially from that of oestrin injection 

 (see p. 119) in that the ovary is stimulated to ovulation. 

 Similar results on mice showing spontaneous ovarian deficiency 

 have been reported by Loewe, Voss and Pass (423). 



(0 THE MECHANISM OF OVARIAN REGULATION 



Influence of the anterior pituitary on the ovary. The work 

 described above makes it evident that the anterior pituitary 

 body produces a substance or substances which have a most 

 potent action upon the ovary, and it is thus reasonable to 

 suppose that the anterior pituitary plays some part in regulating 

 the normal ovarian cycle. The fact that precocious oestrus can 

 be induced in the ovaries and accessory organs of the normal 

 immature animal by administration of anterior pituitary 

 substance, suggests that the first oestrus of puberty is brought 

 about by some action of the pituitary. This, in itself, would not 

 explain how the first oestrus is precipitated: the problem is 

 merely transferred from the ovary to the anterior pituitary. 

 Since anterior pituitary bodies from male or female, young or 

 mature animals are all efficacious, it is difficult to explain how 

 the first stimulus to the ovary is liberated from the anterior 

 pituitary. Smith and Engle (581) ' believe that the hypothesis 

 of the periodic liberation of gonad-stimulating hormone of the 

 pituitary may explain the periodic ripening of groups of follicles 

 more satisfactorily than any previously advanced. ' Whether one 

 or two substances are secreted by the anterior pituitary for 

 the regulation of the ovary is still uncertain, but if two occur it 

 would seem that the first is connected with the maturation of 

 the follicle and the second with the transformation of the 



