86 INTERNAL SECRETION 



interval between ovulations. It is known that pregnancy 

 will not in itself inhibit ovulation. We have seen above that 

 the injection of luteal extracts into fowls will prevent ovulation. 

 It is clear that the ovulation can only be accelerated up to a 

 certain degree by removal of the luteal substance. The 

 succeeding ovulation has to await the maturation of follicles. 

 Without the presence of follicles in a state of maturity, 

 renewed ovulation is impossible, even after extirpation of the 

 corpora lutea. 



The idea that the corpus luteum might be an organ with 

 an internal secretion was first conceived by Gustav Born, who 

 suggested that the function of the internal secretion was to 

 subserve the fixation and development of the impregnated 

 ovum in the uterus. Born did not publish his views, but 

 bequeathed the idea to Fraenkel to work out. It was found 

 by this and subsequent authors that ovariotomy (involving 

 removal of corpora lutea) caused discontinuance of pregnancy 

 in animals. As pointed out by Marshall, there is no evidence 

 that the corpus luteum governs the fixation of the embryo 

 otherwise than by stimulating the uterine mucous membrane 

 to hypertrophy. 



In rabbits spontaneous ovulation and subsequent production 

 of corpora lutea do not occur. The additional stimulus of 

 coition is necessary. Ancel and Bouin observed that, if the 

 follicles be ruptured artificially, corpora lutea are formed and 

 a growth of the mammary glands supervenes. But O'Donoghue 

 found that rupture of the follicles was not always succeeded 

 by the formation of corpora lutea, and when such formation 

 did not occur, there was no growth of the mammary glands 

 (vide infra, p. 88). 



The changes in the uterine mucosa produced by the corpus 

 luteum, and which help in the fixation of the foetus, were studied 

 in greater detail and by a new method by Loeb. It occurred 

 to this observer that the influence exerted by the corpus 

 luteum might be explained if experiments were conducted in 

 which the changes in the uterus could be studied directly, 

 without the interference of a fertilized ovum. Accordingly 

 Loeb excluded the chance of pregnancy by tying the Fallopian 

 tubes immediately after the occurrence of coition. Ordinary 

 foreign bodies and various mechanical stimuli were applied 

 to the uterine mucous membrane. It was found that when 



