THE GENERAL COMPOSITION OF MILK 



Great variations occur, however, and Meigs and Marsh and 

 Kirchner give the averages below : 



The variations are thus considerable, but, generally speaking, 

 cows' milk contains more protein and more salts or ash than human 

 milk. Human milk contains much more sugar, while the amount 

 of fat is fairly equal. It is probable that in reality the average 

 fat content of human milk is higher than that of cows', although 

 it is more difficult to obtain a sample of the milk in such a manner 

 as to ensure a correct result. It is well known that the milk of 

 certain breeds of cows is ' richer ' than others. This term relates 

 mainly to the fat content, although some variation also occurs in 

 the amount of protein. 



Changes in the Composition of Milk occurring at different 

 Stages of Lactation. The milk given by all species of mammalia 

 in the early days after parturition is very different in composition 

 from that given later. The milk of this period is known as colos- 

 trum, and the colostral characteristics persist for different periods 

 in different species, and to some extent also in different members of 

 the species. 



By the end of the first month, however, the colostral charac- 

 teristics have disappeared, and the milk will have the average 

 composition, so far as such an average composition of milk exists. 

 The most pronounced colostral characters have usually ceased by 

 about the fourth or fifth day after parturition. 



