iog6 



REPRODUCTION 



depends on the quantity of fat present, the fat globules, like the blood- 

 corpuscles, being practically non-conductors. 



The inorganic composition of milk is particularly interesting when 

 compared with that of the blood on the one hand and that of the 

 suckling on the other. Thus, 100 grammes of ash from each source 

 gave the following values for the rabbit (Abderhalden) : 



The richness of the milk (and of the suckling) in calcium, phos- 

 phorus, and magnesium, as compared with the serum, is to be especially 

 remarked. This is, of course, essential for the development of the 

 bones. Whereas sodium predominates greatly over potassium in the 

 serum, the opposite is the case in the milk (and the suckling). This is 

 connected with the development of the tissue cells, which are richer in 

 potassium than in sodium. The high chlorine content of the serum is 

 in sharp contrast with the relative poverty of the milk in that element, 

 which preponderates in the tissue liquids and is relatively scanty in the 

 cells. 



In addition to substances susceptible of chemical analysis, milk 

 contains enzymes like those present in blood-serum, including 

 oxydases and various hydrolytic ferments (proteolytic, diastatic, 

 and perhaps lipolytic). It is now universally acknowledged that 

 mother's milk is superior for the feeding of the infant to any 

 artificial substitute, and one factor in this superiority may be the 

 presence of ferments specifically adapted for the digestion of the 

 human suckling. More important is the practical sterility of the 

 human milk and the necessarily finer adaptation of its quantitative 

 and qualitative composition, particularly the closer relationship of 

 its proteins with those of the child. In addition, there is some 

 evidence that the maternal milk contains immune bodies (anti- 

 bodies) which may increase the resistance of the suckling to 

 infections. 



However this may be, there is no question that much of the high 

 infant mortality associated with the industrial conditions of our 

 great cities could be prevented if breast-feeding were carried out by 

 every mother physically capable of it. 



As to the manner in which milk is secreted, there is no doubt 

 that its chief constituents are formed in the gland-cells. Caseinogen 

 and lactose do not exist in the blood or lymph. The former is 



