Constituents of the Ash. 25 
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 
chloride of potash is largely in excess of the 
chloride of soda. This is exactly opposite to the 
proportions of these two salts in the blood. 
Other constituents.—Besides the constituents enu- 
merated above, several other compounds are more or 
less normally present in milk in minute quan- 
tities. 
A small amount of citric acid is said to be a 
normal constituent of milk. 
A peculiar substance called lactochrome is also 
a normal constituent of milk, and gives to it its 
characteristic color. This has been already men- 
tioned in connection with the palmitin. The amount 
of lactochrome present varies under many condi- 
tions, notably the breed of the animal and the 
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