HORMONES AND THE MAMM^ 87 



parturition does not necessarily affect either. I shall 

 consider this matter more fully later. 



The chief questions that we are called upon to Questions to 

 consider here in regard to the mammary glands are : j n reg ard to 

 first, what the hormones are that affect the develop- the 

 ment, growth and function of the mammae ; second, 

 what effect the function of lactation has on the maternal 

 metabolism ; and, last, what, if there be any, are the 

 physiological effects of an extract of mammary gland. 



THE HORMONES THAT INFLUENCE THE MAMMJ3 



Much speculation has existed as to the causal Causal 

 factors in the development and functional activity of the regard* to 



mammae. These glands have, of course, a very definite 

 function to perform in the adult female subsequently and activity. 

 to parturition ; but given sufficient stimulus generally 

 mechanical the mammae of males or virgin females 

 may also be induced to secrete ' milk '. It is certain 

 that the secretion from the breasts of males and virgin 

 women is not of the same composition as that secreted 

 by the normal woman after parturition ; but the fact 

 that such abnormal secretion can occur, although it 

 consists of colostrum only, is of considerable importance, 

 as we shall see directly. It is necessary, moreover, to 

 call attention to a point too well-known to require dis- 

 cussion that has an important bearing on the ultimate 

 understanding of the mammary function : namely, 

 the secretion obtained from the mammae before par- 

 turition is not milk ; that is to say, although during 

 pregnancy the breasts enlarge and the contained glands 

 become active, true milk is not in normal circumstances 

 secreted until some short time after the birth of the 

 child. In this connexion it is interesting also to re- 

 member that milk is usually secreted after the prema- 

 ture birth of a live child, just as it is after full-term 

 parturition. 



It is, therefore, an obvious deduction that, pro- 

 vided lactation has never existed previously, so 



