LACTATION 6ii 



It has been shown that milk can be secreted if the ovaries are 

 removed in the latter part of pregnancy, but it is not clear whether 

 the secretion begins immediately after ovariotomy or whether it is 

 postponed till after parturition.^ 



It is known that the mammary glands undergo normal development 

 in cases of extra-uterine fostation in which the growth of the uterus 

 is relatively small. This observation clearly indicates that the 

 source of the stimulus in question is not to be sought in the hyper- 

 trophied uterus. A consideration of these and other facts led Miss 

 Lane-Claypon and Starling to the conclusion that one or other of the 

 products of conception (i.e. either the foetus or placenta), or possibly 

 both, were the seat of origin of the specific chemical stimulus 

 which brought about mammary growth. 



Halban^ had recently formed the opinion, chiefly on clinical 

 grounds, that the specific stimulus arose mainly in the chorionic villi 

 and placenta. 



Ancel and Bouin have suggested that the stimulus for mammary 

 growth in the later part of pregnancy is produced by the so-called 

 myometrial gland which is said to be located in the muscular layers 

 of the uterus, but according to other observers there is no evidence 

 for this suggestion (see below, p. 618). 



The Fcetal Hormone Theory. — Miss Lane-Claypon and Starling 

 appear to have been the first to deal With the problem experimentally. 

 In an initial series of experiments they injected extracts or emulsions 

 ofTivaries obtained from pregnant rabbits into other rabbits either 

 subcutaneously or intraperitoneally. In two further series of experi- 

 ments rabbits were injected with uterine and placental emulsions or 

 extracts. In no case, however, did the injections produce any effect 

 on the mammary glands, although in certain of the experiments in 

 which ovarian or uterine substance was employed, marked swelling 

 and congestion of the uterus were afterwards observed. 



The effect of injecting foetal extract was next tried, and this led 

 apparently to positive results. When repeatedly injected into female 

 rabbits the extract seemed to produce a genuine development of 

 the mammary glands which simulated the normal growth which 

 occurs during pregnancy. In one case a virgin rabbit received fifteen 

 injections of extract made from many embryos of the same species. 

 The injections were spread over a fortnight, at the end of which the 

 rabbit was killed. It was found that a secretory fluid could be 

 expressed from the nipples, and that on reflecting the abdominal skin 

 all the mammary glands had grown to the size which is ordinarily 



1 Marshall and Jolly, "Contributions, etc.," Phil. Trans., B., vol. cxcviii., 

 1905. 



2 Halban, "Die innere Sekretion von Ovarium* und Placenta und ihre 

 Bedeutung f iir die Function der Milchdriise," Arch. f. Gynak., vol. Ixxv., 1905. 



/ 



