HORMONES AND THE MAMMAE 93 



powerful augmentative influence on mammary secretion Effect of 

 in the lactating animal. This has been confirmed by ^ m^mary 

 Schafer and Mackenzie 1 and others. There has, however, excretion 

 been much discussion whether the extract produces this lactation. 

 effect by its well-known action on all involuntary muscle 

 —an expressor effect, in fact — or whether there is a 

 selective action on the mammary epithelium ; possibly 

 both factors are brought into play. 



I have recently carried out experiments, in which Effect of 

 injections of anterior lobe extract and infundibulin have ^tradiTon 

 been made into adult virgin and into non-pregnant the inactive 

 parous guinea-pigs, in order to test the effect of these 

 extracts on the mammary glands in circumstances which 

 would avoid the possibility and consequent confusion 

 of an expressor action. In these experiments portions 

 of the mammae were first removed as controls, and 

 subsequently the animals received many injections of 

 the extracts mentioned. In no case was any histological 

 difference found in the mammary gland before and after 

 the injections. 2 



The thyroid and the mammae. — Very little Thyroid- 

 experimental work has been recorded in this connexion, n ot°hiLrfere 

 In ray own experiments it was noted that in one cat from with ™ ilk - 



. . secretion 



which the thyroid had been removed during pregnancy during 

 suckling occurred after the birth of the kittens. This lactatlon 

 showed that, like the removal of ovaries, thyroidectomy 

 does not interfere with the milk-secretion provided the 

 breasts be active — that is, under the influence of preg- 

 nancy — at the time. In animals from which the thyroid 

 is removed at other times inactivity persists, as we 

 would expect. 



According to Ott and Scott 3 , iodothyrin inhibits Effects of 

 mammary secretion. On the other hand Hertoghe 4 ^ e o c t ^° n ^ f 



1 Schafer, E. A., and K. Mackenzie, Proc. Roy. Soc. t Ser, B, 

 1911, vol. lxxxiv, p. 16. 



2 Bell, W. Blair, The Pituitary, 1919. 



3 Ott, I., and J. C. Scott, Therap. Gaz., 1912, vol. xxxvi, p. 761. 



4 Hertoghe, E., quoted by H. R. Harrower, Practical Hormone 

 Therapy, 1914, p. 186. 



