506 Dr. J. E. Lane-Claypon and Prof. E. H. Starling. [Feb. 12, 



temporary enlargement of the gland, and during the whole of adult life the 

 glands remain in the female at the same state of development unless 

 pregnancy occurs. The commencement of pregnancy acts as an impetus to a 

 further great development of the gland substance, a development which, as 

 we shall see shortly, differs in some respects from that which gave rise to the 

 growth of the gland at puberty. This hypertrophy continues throughout the 

 whole of pregnancy, being more rapid as pregnancy advances. 



With cessation of pregnancy, whether abnormally or at the normal term, 

 the growth of the glands at once comes to a stop, and two or three days after 

 this cessation the activity which previously was spent on growth is now 

 applied to the secretion of milk, a secretion which, if the gland is emptied 

 periodically, lasts for many months. 



This whole cycle of changes can be prevented by the removal of the 

 sexual glands, namely, the ovaries, and these organs must therefore be 

 regarded as primarily responsible for the growth of the mammary glands. 

 We shall have to consider later on whether they are the immediate source of 

 the impulses which induce the growth of the gland during pregnancy and its 

 secretory activity after parturition. We must conclude, however, that there 

 is some impulse or impulses arising in the ovaries, uterus, or product 

 of conception, which exerts a direct influence on the mammary glands, and is 

 responsible for their hypertrophy. 



What is the nature of this connection ? The well-known nervous 

 connections between the mammary glands and the uterus, instanced by the 

 occurrence of uterine contractions on stimulation of the nipples, has been 

 taken to indicate that the impulses which cause growth of the glands are 

 also nervous in character. Although this view is still sustained by certain 

 physiologists, e.g., K. Basch,* there are many facts, experimental as well as 

 chemical, which place such an explanation out of court. Thus in a goat 

 Eckhardf cut all the nerves to the mammary glands without appreciably 

 affecting the yield of milk from the denervated gland. KibbertJ transplanted 

 in the guinea-pig one of the two mammary glands to the neighbourhood of the 

 ear, thus dividing all its nervous connections. In a subsequent pregnancy 

 this gland enlarged as usual, and milk could be obtained from it at the end of 

 pregnancy. 



Still more definite evidence is afforded by the well-known case in which 

 Goltz and Ewald§ removed the whole of the lumbo-sacral cord in a pregnant 



* 'v. Ergebnisse der Pliysiologie,' vol. 2, 1, p. 325, etseq., 1903 ; also Bibliography. 



t ' Eukhard's Beitrage,' vol. 1, p. 18. 



I ' Archiv f. Entwickeluugsmechanik,' 1898. 



§ ' Pflliger's Archiv,' vol. 63, p. 385. 



