150 The Endocrine Organs 



Internal Secretion of Mammary Gland 



A similar galactagogue effect was obtained by Mackenzie as the result 

 of intravenous injection of extract of lactating mammary gland (fig. 104) : 

 no result was obtained from the gland of non-lactating animals. 



Adler found subcutaneous injection of extract of mammary gland to produce 

 enlargement of the suprarenals and increase of adrenalin in the blood, some- 

 times sufficient to cause glycosuria. He also found it to arrest the development of 

 the embryo, and even to produce abortion in pregnant animals. These observations 

 require confirmation. 



Internal Secretion of Placenta 



Halban has suggested that the placenta furnishes the stimulus for the 

 development and growth of the mammary glands, whilst inhibiting the 

 pouring out of their secretion. That the former is improbable is indicated 

 by the fact that the mammae may become developed in exceptional cases 

 in the virgin, and even in the male sex. 1 The second suggestion has 

 received some support from, the experiments of Mackenzie, who found that 

 injection of placental extract tends to inhibit the effect of such galactagogue 

 extracts as pituitary or corpus luteum. A similar result was obtained by 

 Mackenzie with extrac't of foetus, which also has been described as promot- 

 ing mammary development. 2 It would seem, therefore, that both placenta 

 and foetus produce chalonic autacoids which have an inhibitory effect on 

 milk secretion. As a commentary on this, it may be noted that secretion 

 by the mammary gland does not begin until the removal of any influence 

 which might be derived from placenta or foetus. 



1 As W. Heape has pointed out, this objection is also applicable to the foetal hormone 

 theory of Starling and Lane-Claypon (see below). 



2 By Starling and Lane-Claypon, and by Foa. There seems to be some doubt whether 

 the changes described were a specific effect of the foetal extract. 



