THE GENERATIVE GLANDS 409 



mortem examination subsequently showed that there was no 

 " spurious " corpus luteum. It is very evident from this experi- 

 ment that the corpus luteum is not indispensable to either the 

 nidation of the ovum or to its after development. Frankel 

 explains the results of this experiment by assuming that, in this 

 instance, the function of the corpus luteum was vicariously under- 

 taken by an atretic follicle, but this assumption is a complete 

 departure from his own theory. For, as we know, the atretic 

 follicle is entirely a connective tissue structure and the theca-lutein 

 cells, formed in the course of its involution, compose the inter- 

 stitial ovarian tissue. This proves the importance of the inter- 

 stitial gland in the nidation of the ovum, while at the same time 

 it reduces the function of the corpus luteum to a probable partici- 

 pation in this process. 



Having disposed of Born and FrankePs hypothesis, we return 

 to the view, first expressed by Prenant and since confirmed by 

 others (Sandes, Srobansky), that the internal secretory function 

 of the corpus luteum persistens consists in the inhibition of 

 ovarian activity and, more especially, in the prevention of ovula- 

 tion during pregnancy. 



It is common knowledge that, as a general rule, neither 

 ovulation nor menstruation take place in pregnant women. In 

 the cow, persistence and hypertrophy of one corpus luteum are by 

 no means infrequent findings, and in such cases there is no 

 recurrence of rut at the usual intervals of twenty-one days ; if the 

 hypertrophied corpus luteum is removed by surgical means, how- 

 ever, the signs of rut will appear a few days later. In the case 

 of the mouse, the corpus luteum persists after littering, sometimes 

 until after the second or 'even third pregnancy (Sandes, after 

 Mandl). 



Ravano shows thaMfhe current notion that, in women, the 

 corpus luteum graviditatis persists during the entire period of 

 pregnancy, is mistaken ; it may even completely disappear, 

 though the occurrence is rare. In about 5 per cent, of cases, 

 complete ovulation takes place during pregnancy, while a ten- 

 dency to ovulation is shown by the large majority of pregnant 

 women . 



The material we at present possess supplies no decisive 

 evidence as to the part played by the corpus luteum in the 

 inhibition of ovulation and the other ovarian functions during 

 pregnancy. As we have previously shown, these processes may 

 result, with equal probability, from hyperfunction of the inter- 

 stitial cells and reduction of activity on the part of the other tissues, 

 particularly of the Graafian follicles. The atresia, which extends 

 during pregnancy to numerous follicles, consumes the material 

 for the maturing of the ovum. 



It is evident from the above that the third and most con- 

 siderable tissue constituent of the ovary, the Graafian follicles, 



