CONTENT OF COW'S MILK 5 



65° C. and 80° C. They become of practical importance in 

 relation to the pasteurisation of milk and its detection (see 

 Chapter XX.). 



Vieth has shown, and this has been abundantly confirmed, 

 that there is a definite ratio existing among the components of 

 the non-fatty solids of normal milk. This ratio is expressed 

 as follows : 



Sugar . . 13 



Proteids . 9 



Ash , 2 



With milk containing nou- fatty solids = 8'9 per cent, this 

 gives 



Sugar 4-82 



Proteids 3 -.3 4 



Asli . . 0-74 



3-90 



These percentages agree closely with the figures given above. 



Eevis^ has pointed out that results of numerous analyses 

 show that (ff.) When genuine milk is deficient in non-fatty 

 solids, the deficiency is due entirely to an abnormally low per- 

 centage of milk sugar, the proteids and ash being present in 

 their normal amounts, (b) When a genuine milk shows an 

 unusually high percentage of non -fatty solids, the increase is 

 due almost entirely to an abnormally high percentage of the 

 proteids, the sugar and ash either remaining normal or perhaps 

 slightly increasing also. 



The importance of this fact lies in its relationship to the 

 detection of added water in milk. If water is added to milk 

 Vieth's ratio is not, of course, affected, and the sugar should 

 stand at ^^ of the solids not fat. If the diminution met with 

 in the non-fatty solids is a natural one, the percentage pro- 

 portion of milk sugar should be considerably less than -|^- of 

 the estimated non-fatty solids. The amount of sugar can be 

 estimated polarimetrically. 



While the nature and physical conditions of the proteids, 

 fats, carbohydrates, and salts of milk are of great importance in 

 relation to infant-feeding, these considerations are of no special 

 significance from the point of view of the present work. From 



> Journ. Boy. Ids/, of Public ffealth, 1908, vol. xv. p. 39. 



