55 



PART IV. THE PRODUCT MILK. 



Milk is an opaque, whitish liquid secreted by female mammalia 

 for the njuitrition of their young. In the case of the cow, and some 

 other animals used to supply milk for human consumption, the 

 function of milk production has been so developed by breeding and 

 selection that the yield is much greater than is required for the 

 sustenance of their young. The length of their period of lactation 

 has also been increased much beyond the time that the yowng would 

 be dependent upon the mother's milk. 



The processes of the elaboration of milk are not very well under- 

 stood. The seat of secretion is however undoubtedly in the mammary 

 glands, though some believe that the water and some of the soluble* 

 compounds are derived by direct nitration from the blood. 



The udder is not merely a reservoir for the milk between the 

 time it is manufactured and drawn. Indeed it is evident that a 

 great part of the milk is made du/ring the actual operation of milking, 

 as is shown by changes in quality and quantity resulting from any 

 unaccustomed action, such as quick instead of slow milking, or a 

 change of milker. 



Milk is a food, and, of all foods, comes nearest to meeting all 

 demands of the body. It is, in fact, a complete food for the young. 

 Its constituents in their proportions in average milk are as 

 follows : 



Constituents. Quantity., 



Per cenfc. 



Water 87-0 



Ash 0-7 



Albumen 0-7 



Casein ' 2-6 



Fat 4-0 



Sugar 5-0 



In analysis these are spoken of as water and milk solids, the 

 latter comprising the ash, albumen, casein, fat and sugar. Th< 

 solids again are divided into ' Fat ' and ' Solids, not fat.' Milk 

 standards are fixed by Provincial Statute in Canada hence no uniform 

 Canadian standard may be said to exist, but it usually requires that 

 there be no more than 87-5 per cent water, that the total milk 

 solids shall make up at least 12-5 per cent, and that there b at least 

 3 per cent fat. 



