816 THE VARIABILITY OF COWS' MILK, i., 



the first knowledge of the quantitative variation of the composition 

 of cows' milk was obtained. 



Towards the end of the eighteenth century, man's attention 

 began to turn seriously to the quantitative investigation of the 

 composition of substances; and, during that period, Parmentier 

 and Deyeux (1790) published their quantitative analyses of cows' 

 milk, wliich are among the first recorded. By that time, a fairly 

 complete knowledge of the qualitative composition had already 

 been acquired. As early as 1615, Bartoletti had shown that milk 

 contains a sugar, in addition to fat and the cheese-forming sub- 

 stance known even then. 



The first quantitative analyses of milk were, no doubt, of purely 

 scientific interest, but, as the dairying industry has grown, and the 

 output of its products has increased, the demand for precise 

 methods for determining the value of these products has become 

 more insistent. For milk is the most easily adulterated of foods. 

 Its bulk may be increased by the mere addition of water, and the 

 unscrupulous milk-vendor has been only too ready to avail himself 

 of this simple method of adding to his profits. lii all civilised 

 countries, therefore, administrative bodies have been appointed 

 to control the sale of milk and of other foods. On the 

 recommendation of these bodies, standards are fixed by 

 law from time to time. To these standards all milk 

 produced for sale is required to conform. The standards 

 vary in different countries, and in different districts of the 

 same country. They were primarily devised for the detection 

 of the addition of water to milk, and generally consist of state- 

 ments of the percentage values of certain constituents, fat, solids 

 not fat, and total solids, below which the values in the milk sold 

 may not fall. The addition of substances foreign to the milk to 

 preserve it is also forbidden, and, recently, a certain value of the 

 freezing point has been added to the standards required in some 

 districts. 



As a result of these regulations, the chemical examination of 

 milk lias become a daily necessity, and, in the last quarter of a 



