30 



Scientific Proceedings (6i). 



17 (949) 



The action of pituitrin on the secretion of the mammary gland. 



By Sutherland Simpson and R. L. Hill. 



[From the Department of Physiology and Biochemistry, Medical 

 College, Cornell University, Ithaca, N. Y.) 



The administration of pituitary (posterior lobe) extract to a 

 lactating animal by subcutaneous, intramuscular or intravenous 

 injection causes an increased flow of milk from the mammary 

 gland. In view of the fact that the response is so rapid (the 

 latent period is usually from 20 to 30 seconds) it would not be 

 unreasonable to suppose that the extract acts on the non-striped 

 muscle of the gland, causing an expulsion of the milk already 

 there, rather than on the secretory mechanism, leading to an 

 increased production of milk. 



Pituitary extract is known to contain a substance which 

 excites non-striped muscle generally. The ducts and lactiferous 

 sinuses of the mammary gland contain non-striped muscle and 

 it is claimed by some that this tissue is also represented in the 

 alveoli. 



To determine whether the flow of milk which follows the intra- 

 venous injection of pituitrin is due to stimulation of plain muscle 

 the following experiment was performed. A lactating female dog 

 was anesthetized, cannulas were introduced into the carotid artery 

 and femoral vein, and the milk-flow recorded on a revolving drum 

 by the exudation method of Schafer and Mackenzie, 1 a blood 

 pressure tracing being taken at the same time. One c.c. of a 1 per 

 cent, solution of barium chloride was injected into the femoral 

 vein ; this was sufficient to produce a marked rise in blood pressure 

 and a slowing of the heart, but there was no increase in the rate 

 of milk flow. Shortly afterwards I c.c. of Parke, Davis & Co.'s 

 pituitrin was injected into the vein; this was followed by a rise 

 in blood pressure and at the same time a copious flow of milk. 



This simple experiment would seem to prove that the action 

 of pituitrin on the mammary gland is secretory rather than 

 muscular. 



1 Schafer and Mackenzie, Proc. Roy. Soc, B, Vol. 84, 191 1, p. 16. 



