CHAPTER XVI. 

 MILK. 



The qualitative composition of milk as produced by the 

 mammary glands of different animals is nearly the same what- 

 ever the species of animal. But in quantitative composition 

 very great differences obtain. Cow's milk has always been 

 taken as the type with which comparisons are made, as it is 

 the kind everywhere in general use. The essential differences 

 between it and mother's milk will be pointed out in what 

 follows. 



COW'S MILK. 



In an earlier chapter an analysis of cow's milk is given 

 which represents a general average of composition of good 

 market milk. But the normal milk of individual cows may 

 be very different from that there described. The qualitative 

 composition is always the same, 'but in the amounts of fat, 

 sugar and protein present the greatest divergences are noticed. 

 These variations depend on the race of the animal, the period 

 of lactation and especially on the feed. It is also a well- 

 known fact that the richness of milk varies during the time 

 of milking, the first portions of milk withdrawn from the 

 udder being poorer in fat than the last part or " strippings." 

 In speaking of normal milk, then, these facts must be kept in 

 mind ; a milk may be normal but not necessarily rich or good, 

 from the standpoint of food value. The following table illus- 

 trates the variations found in the analyses of milk from a large 

 number of cows. The mean specific gravity is from 1.029 to 

 1-033- 



Mean. Maximum. Minimum. 



Water 87.4 91.5 84.0 



Fat 3.5 6.2 2.0 



Sugar 4.5 6.1 2.0 



Proteins 3.9 6.6 2.0 



Salts 0.7 i.o 0.3 



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