1298 PHYSIOLOGY 



the source of the inhibitory stimulus is removed and the overgrown gland 

 cells enter into a condition of spontaneous activity. However this may be, 

 there is no doubt that the secretion of the gland, once formed, is continued 

 independently of the foetus or indeed of any of the pelvic organs. The 

 onset of a IIQW pregnancy brings the secretion to a close. Removal of 

 the ovaries in a cow is sometimes employed as a means of prolonging the 

 secretion of milk. The only condition in the human being, which is 

 necessary for secretion to continue during six to nine months after birth, 

 is the repeated emptying of the gland, i. e. the removal of the secreted 

 milk. The process of suckling not only removes the milk already secreted 

 but excites the secretion of more milk. The secretion is certainly subject 

 to nervous influences, but physiologists have not succeeded in either pro- 

 ducing secretion by stimulation of the nerves going to the glands, or in 

 stopping secretion by section of these nerves. Moreover the food of the 

 animal may be varied within very wide limits without altering the composi- 

 tion or amount of the milk secreted, provided that the food is sufficient 

 in amount. The only constituent of the milk for which we have direct 

 evidence of alteration by changes in the food supply of the mother is the fat.. 

 It is well known that the composition of butter may be affected according to 

 the food supplied to the cow. A large supply of oilcake, for instance, may 

 result in the production of a butter which is deficient in the higher fatty acids 

 and is therefore oily at ordinary temperatures. Abnormal fats and fatty 

 acids such as iodised fats or erucic acid, when administered to an animal in 

 lactation, may appear among the fats of the milk. Not only can the secretion 

 and composition of the milk be affected reflexly through the nervous system, 

 as e. g. under the influence of emotions, but the influence may be reciprocal. 

 This is especially marked in the case of the pelvic organs. The act of 

 suckling excites tonic contractions of the uterus. Putting the child to the 

 breast shortly a{ter birth is therefore an important means of causing 

 contraction of the uterus and stopping any tendency to haemorrhage from 

 the venous sinuses opened by the separation of the placenta and fcetal 

 membranes. The nursing of the child is thus an important means of 

 procuring a proper involution of the uterus after labour. Many uterine 

 troubles among women may be ascribed to the previous neglect of this 

 elementary duty. 



