HORMONES AND THE MAM1VLE 95 



" the action of a specific chemical stimulus produced in The question 

 the fertilized ovum "*. hormone 



Further, they stated that " lactation is due to the affecting the 



J mammae. 



removal of this substance, which must therefore be 

 regarded as exerting an inhibitory influence on the gland 

 cells, hindering their secretory activity and furthering 

 their growth ". 



These authors, however, do not believe that the 

 foetus is the only factor concerned in activating or 

 inhibiting the mammary development — a reservation 

 that has often been overlooked by subsequent writers 

 who have alluded to this work. 



Lane-Claypon and Starling found, then, that the Foetal hor- 



, , n • • • i -i i mone is not 



mammary glands of virgin animals were stimulated to specific. 



growth by foetal extract, and those of muciparous 

 animals to secretory activity. These observations have 

 been supported by other evidence ; but Foa's 2 investi- 

 gations seem to show that the hormone is not specific 

 to the species. 



Before Lane-Claypon and Starling's researches 

 Halban 3 had put forward the view that the stimulus 

 to mammary development during pregnancy originates 

 in the placenta. 



On the other hand, the views put forward by Lane- 

 Claypon and Starling have been criticized. 4 Never- 

 theless, it is evident that the claim of these observers 

 concerning the foetal hormone is accurate so far as it 

 goes ; but, as they themselves admit, this explana- 

 tion does not contain the whole truth of the matter, for 

 it seems that many organic extracts have the same 

 effect as foetal extract. 



Hill, quoted by Marshall 5 , and O'Donoghue 4 state 



1 Lane-Claypon, Janet E., and E. H. Starling, Proc. Roy. Soc., 

 Ser. B, 1906, vol. lxxvii, p. 505. 



2 Foa, C, Archiv. di Wis., 1908, vol. v, p. 520. 



3 Halban, J., Archiv. f. Gynak., 1905, vol. lxxv, p. 353. 



* O'Donoghue, C. H., Quart. Journ. Micr. Sci., 1911, vol. lvii, 

 p, 187. 



8 Marshall, F. H. A., The Physiology of Reproduction, 1910, 

 p. 57(3. 



