334 THE PHYSIOLOGY OF REPRODUCTION 



have described congestion in the uterus after the injection of 

 ovarian extract ; but, in their experiments, the ovaries employed 

 were those of pregnant animals. 



Further evidence that the prooestrous and cestrous conditions 

 are produced by substances circulating in the blood, but not 

 necessarily elaborated in the ovaries, is supplied by certain facts 

 recorded by Halban. 1 This author affirms that the milk of 

 suckling sows is affected during the periods of heat, in conse- 

 quence of which the young are liable to develop unhealthy 

 symptoms." In a similar way the milk of women is said to 

 be affected during menstruation. Moreover, according to 

 Youatt, 2 cows can be brought " on heat " artificially by feeding 

 them on milk supplied from other cows which are in that con- 

 dition. 



Heape 3 has suggested that heat may be due to a " generative 

 ferment " which he supposes to be periodically present in the 

 blood. At the same time he is of opinion that a hypothetical 

 substance called " gonadin," which is secreted by the generative 

 glands, is also an essential factor. The precise relation in 

 which gonadin and the generative ferment are supposed to 

 stand to one another is not at present clear, but there is no in- 

 consistency between a belief in their existence and the views 

 which are adopted here. 



Assuming that heat and menstruation are brought about, 

 either directly or indirectly, through a stimulus depending upon 

 the secretory activity of the ovary, it is still an open question 

 as to what part of the organ is concerned in the process. 

 Fraenkel 4 has supposed that the secretion in question is supplied 

 by the corpus luteum. This conclusion is based upon nine 

 cases in which the corpus luteum was destroyed by the cautery, 

 and in eight of which the next menstrual period was missed. In 

 the remaining case it is supposed that the secretion responsible 

 for producing menstruation had already been formed in sufficient 

 quantity and passed into the circulation at the time of the 

 cauterisation. FraenkeFs theory, however, is disproved by the 



1 Halban, loc. cit. 2 Youatt, Cattle, London, 1835. 



3 Heape, " Ovulation and Degeneration of Ova in the Rabbit," Proc. Roy. 

 Soc., B., vol. Ixxvi., 1905. 



4 Fraenkel, "Die Function des Corpus Luteum," Arch. /. Gyndk., 

 vol. Ixviii., 1903. 



