THE GENERATIVE GLANDS 373 



been disproved. An experiment by Goltz and Ewald is interesting 

 in this connection. These authors found that, after extirpation of 

 the entire lumbo-sacral portion of the spinal cord of a bitch, the 

 mammas underwent normal enlargement during pregnancy, and 

 that lactation after parturition was also normal. Ribbert trans- 

 planted the mammary gland of a guinea-pig into the neighbour- 

 hood of the ear, and found that it hypertrophied during pregnancy 

 and secreted milk after parturition. 



There is, then, no doubt that the growth of the mammary 

 glands during pregnancy is the result of a chemically active 

 stimulant. The next step is to discover the source of origin of 

 this hormone. Pregnancy is associated with changes in the 

 ovary (formation of the corpus luteum verum) and in the uterus 

 (development of the muscles and mucosa) ; the foetus, moreover, 

 develops ; and from the combined maternal and fcetal tissue the 

 placenta, an organ by which the foetus obtains nourishment, is 

 formed. The active hormone may be the product of any one of 

 these four factors. Consideration of the clinical material which 

 the subject offers led Halban to the conclusion that neither the 

 ovary nor the uterus is the source of the hormone. In the first 

 place, castration early in pregnancy does not prevent the hyper- 

 trophy of the mammae, and castrated women are able to suckle 

 their children ; in the second place, the development of the mam- 

 mary glands is constant in extra-uterine pregnancy, in which the 

 uterine hypertrophy is slight; and in the third place, after 

 extirpation of the uterus, secretion of milk takes place in the same 

 way as under normal conditions. 



It would appear from this that the cause of the hyperplasia 

 must lie with the ovum, that is to say, with either the foetus or 

 the placenta. From the fact that pregnancy changes take place 

 in the mammas where the embryonic body is absent, as, for 

 instance, in molar pregnancy, Halban concludes that the stimulus 

 cannot be supplied by the foetus; by a process of exclusion he 

 thus arrives at the result that the source of origin of the hormone 

 is the placenta, especially the trophoblast and the chorion 

 epithelium. Similarly, he regards the growth of the mammas in 

 the foetus at the eighth lunar month, as due to reaction on the 

 part of the foetal tissue to the stimulatory action of the placental 

 substance. 



According to Halban, then, the substances supplied by the 

 ovary and, the placenta produce similar results, those produced by 

 the placental substance being, however, much more intense. 

 During pregnancy, when the ovary ceases to be active, its internal 

 secretory function is undertaken by the placenta, by which it is 

 very much intensified. 



Starling and Lane Claypon endeavoured to discover the origin 

 of the hormone by experimental measures. They injected extract 

 of foetus, ovary, and uterine mucous membrane under the skin 



