408 INTERNAL SECRETION 



the Graafian follicles are the sole agents in the prevention of the 

 uterine atrophy, is proved in the most conclusive manner by a 

 case of Bucura's, in which a remnant of the ovary was left in 

 situ after castration, and in which atrophy of the uterus did not 

 take place. Examination of sections in unbroken series showed 

 that this remnant consisted solely of maturing Graafian follicles, 

 neither stroma cells nor any traces of corpus luteum being present. 



Bern's original hypothesis, that the function of the corpus 

 luteum is to provide for the nidation in the uterus and subsequent 

 development of the fertilized ovum, finds considerable support in 

 the results of morphological investigation as well as in Frankel's 

 experiments. If the ovum, after its emergence from the Graafian 

 vesicle, becomes fertilized, lutein cells are formed from the 

 epithelial cells of the membrana granulosa, probably in the same 

 way as at the menstrual period ; but the corpus luteum of preg- 

 nancy persists and, in accordance with both its genesis and 

 structure, may be regarded as a secreting gland. What is the 

 nature of its function ? The similarity of structure and develop- 

 ment which subsists between the menstrual and the gestative 

 corpora lutea, inevitably suggests that the latter carries out, only 

 in a more intense degree, the function inaugurated by the former- 

 If the corpus luteum menstruationis prepares the uterine mucosa 

 for the reception of the ovum, the corpus luteum graviditatis is- 

 responsible for the nidation of the fertilized ovum and for its 

 further development. But, seeing that we are unable to attribute 

 the responsibility for the menstrual changes in the mucosa to the 

 corpus luteum menstruationis, the premises for the conclusion that 

 the corpus luteum graviditatis also possesses a preparatory 

 function cease to exist. On the other hand, Frankel's experi- 

 ments undoubtedly appear to bear this interpretation. These 

 experiments show that in the rabbit, suppression of the corpora 

 lutea in the first week after fertilization prevents the occurrence 

 of pregnancy, and that suppression between the eighth and 

 twentieth days terminates it. With regard to the latter point,, 

 however, Kleinhans and Schenk found by very careful experiments 

 that the removal of the corpora lutea after nidation does not 

 necessarily terminate a pregnancy of more than nine days' dura- 

 tion, and it seems evident from this that the corpus luteum has- 

 no significance in the after-development of the ovum. 



The function of the corpus luteum could only be to safeguard 

 the nidation of the ovum. But even this manifestation of activity 

 seems improbable in the light of an experiment carried out by 

 Mandl. The left ovary of a pregnant rabbit was removed and 

 implanted between the fascia and the abdominal wall. After 

 littering, pregnancy again took place, and two days later the 

 second ovary was removed. The pregnancy ran a normal course, 

 in spite of the fact that a corpus luteum graviditatis could not 

 possibly have been present in the transplanted ovary, and post- 



