298 



THE CHEMICAL COMPOSITION OF MILK. 



The maximum individual differences varied from +046 to 

 0-4:4, or nearly 0-5 per cent. 



It is seen from the above table that there is a very slight 

 tendency for the proteins to be higher when the fat is high, but 

 the tendency is very much less than that indicated by Timpe's 

 formula. 



H. C. Sherman finds that a milk rich in fat is generally rich 

 in proteins, the excess of protein above the normal averaging 

 one-third of the excess of fat. 



Variation of Constituents of Solids not Fat. Yieth 

 gives the average proportion between milk-sugar, protein, and 

 ash in milk as 13 : 9 : 2, 



The author has found that this ratio is marvellously exact, 

 the average being 



Milk-sugar, 52-8 % as against 54-2 calculated from Vieth's ratio. 



Protein, 37-8 37-5 



Ash, 8-3 8-3 



In order to ascertain whether all the constituents of the solids 

 not fat vary directly as the total percentage, or whether an 

 excess or deficiency of solids not fat is due to excess or deficiency 

 of any one constituent, the author has examined a large number 

 of analyses of milk in which milk-sugar, protein, and ash were 

 determined. On plotting out the average figures for solids not 

 fat against each of the constituents, the figures for milk-sugar, 

 protein, and ash lie each in a series of three straight lines. For 

 each constituent the breaks occur between 8-8 per cent, and 

 8-9 per cent., and between 8-4 per cent, and 8-5 per cent., and are 

 quite well defined. It is suggestive that the one figure is very 

 near the average percentage, and the other is almost that adopted 

 as the limit for normal milk, and the figures show that it would be 

 difficult to dilute down a milk high in solids n t fat without arous- 

 ing a strong suspicion that it is watered. Table LV. gives the 

 average figures deduced ; individual samples may show differences 



TABLE LV. 



