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THE CHEMISTRY OF MAN. 69
again converted into it, gives a similar result. In 1,000
parts :
Water 883-6 I Casein (cheese) 34-3
i Butter 25-3 Sugar of milk, etc 482
Salts 2-3
Cow's milk, the most commonly used for food, may
be compared with the above by the following analysis.
In 1,000 parts :
Water 821-8 I Casein 67-0
Butter 55-0 I Sugar, etc 51-0
Salts, etc 13-0
The atomic composition of the proteian compounds,
albumen, fibrin, and casein, is carbon, 40 ; hydrogen,
31 ; nitrogen, 5; oxygen,, 12; or by Liebig's formulary,
C 48, H 36, N 6, O 14.
Crystals of the sugar
of milk contain carbon, 12;
hydrogen, 12 ; oxygen, 12.
The animal fats and acids are composed
of these
three elements, as are the vegetable oils, starch, sugar,
and acids.
By certain changes in the arrangement of the atoms,
and sometimes in their we proportions, have starch
converted into sugar, fat, alcohol, acid. Sugar is con
verted readily into fat by the digestive process, and into
alcohol and acid by fermentation.
Thus we have the three elements, carbon, hydrogen,
in our
and oxygen, composing the heat-giving principles,
food, and nitrogen added to form the animal tissues.
Much of what is stated here will seem more clear
and important, when it is applied to physiology, in what
is to follow.