Milk Sugar and Ash 25 
The sugar.— Milk sugar, otherwise called lactose, 
exists in solution in the milk serum. It has the 
same chemical composition as cane sugar: that is, 
CwH»O0n + H20. It crystallizes with considerable 
difficulty, and has very much less sweetening power 
than ordinary sugar. Under the influence of vari- 
ous ferments it readily undergoes decomposition, 
each molecule of sugar breaking up into four mol- 
ecules of lactic acid. This change begins in the 
milk almost immediately after it is drawn, and con- 
tinues until from .8 to 1 per cent of lactic acid 
is formed. The presence of lactic acid in this 
amount acts as a check upon the growth of the 
ferments, and prevents the further formation of 
lactic acid, unless the acid is neutralized with an 
alkali, when the fermentation proceeds as_ before. 
Milk sugar does not readily undergo alcoholic fer- 
mentation, but by the action of yeast and some 
other ferments the lactose is “inverted,” or changed 
to dextrose and a peculiar substance known as ga- 
lactose, and these readily change to alcohol under 
the influence of the proper ferments. 
The ash.—The ash is the smallest and least 
variable constituent of the milk. It is composed 
chiefly of the phosphates of lime and potash, the 
chlorides of potash and soda, with small amounts 
of phosphate of iron and magnesia. Most of the 
salts are in solution. It seems probable that at 
least a part of the phosphate of lime is ordinarily 
in insoluble form, suspended in the milk in very 
fine particles in connection with the casein. The 
