16 



The Action of Animal Extracts on Milk Secretion. 

 By E. A. Schafer, F.R.S., and K. Mackenzie, M.B., Ch.B. 



(Received March 7— Bead March 9, 1911.) 

 (From the Department of Physiology, University of Edinburgh.) 



Since the secretion' of milk is known to proceed with the same regularity 

 whether the nerves to the mammary glands are cut or intact*, it seems 

 probahle that it is provoked by other than nervous stimuli. It cannot, 

 indeed, be contested that the secretion is influenced through the nervous 

 system, but this may be indirect, if the formation and outpouring of the 

 secretion can be shown to be produced by chemical agents (hormones) 

 circulating in the blood, such as have been found to excite secretion in the 

 pancreas,t which is stimulated to active secretion by a material obtained 

 from the mucous membrane of the duodenum, and in the kidney ,% which is 

 stimulated by a material yielded by the posterior or infundibular portion of 

 the pituitary body. 



We have investigated the action of a large number of animal extracts 

 upon the flow of milk from the mammary glands of lactating animals, 

 chiefly cats, but including some dogs. The extracts, which were made with 

 Pdnger's solution, and were in most cases previously boiled, were injected 

 slowly and in small amount (not more than 5 c.c. at a time) into a super- 

 ficial vein,- and the flow of milk, if any, was recorded by one of two 

 methods, or by both methods simultaneously. The simpler method 

 consists in recording the rate of exudation of milk from a small and 

 superficial cut into one of the mammary glands (exudation method). The 

 other method consists in recording the flow of milk led from a canula tied 

 into a cut nipple (nipple method) ; in either case the milk is allowed to 

 drop upon an electric recorder, and the drops are marked by an 

 electromagnetic signal upon the paper of a kymograph. On this paper 

 are also recorded at the same time in some of our experiments the 

 blood-pressure, the volume of the kidney, and the rate of excretion of 

 urine. The animals were anaesthetised either with chloroform alone or 

 with chloroform followed by chloral, the latter being administered either 

 intravenously or subcutaneously ; after the complete effect of the chloral is 

 established, the chloroform administration is stopped. 



* Eckhard, ' Beitrage zur Anat. u. Physiol.,' 1855 and 1897. 



t Bayliss and Starling, ' Journ. Physiol.,' 1902, vol. 28, and 1903, vol. 29. 



| Schafer and Herring, ' Phil. Trans./ 1906, B, vol. 199. 



