ir digestion. It is
therefore not surprising that seven eighths of milk is composed of
water. Blood contains a similar proportion, and this agreement
emphasises the fact that milk is a perfectly balanced food.

The fat of milk, which yields cream and butter, differs in some
important respects from other fats. Like these, it is made up chiefly
of stearin, palmitin, and olein, but, in addition, it contains an
abnormally large proportion of compounds of certain of the volatile
fatty acids. It is these which give to butter its agreeable flavour. By
the methods of Duclaux, the following is the approximate composition of
butter fat:

Per cent.
Stearin, palmitin, olein, and traces of
myristin and butin 91.50
Butyrin 4.20
Capronin 2.50
Caprylin, caprinin, and traces of laurin 1.80
-----
100.00
------

Myristin occurs in nutmegs; butyrin in another combination flavours
pineapples and rum; caprinin is found in cocoanut fat, mutton fat, and
in the offensive odour given off by the goat (from which the name is
derived); caprylin is a by-product of alcoholic fermentation, and also
occurs in cocoa fat; laurin is found in sweet bay; from which it is
evident that there are some curious relationships in flavouring
materials.

Fats are very concentrated foods, furnishing a large amount of energy to
the body. At one time they were classed together with starch, sugar,
and other carbohydrates as heat-producers, but the distinction which
was drawn between the kinds of food which were thought solely to keep up
the temperature of the organism, and those which produced force in work
and other forms of bodily energy, has broken down, and by direct
experiment has been found not to exist. It is usually calculated that
one part of fat is equal in food value to about two and a quarter parts
of any of the other carbohydrates. Milk fat or butter is more digestible
than almost any other fat, and its importance therefore can readily be
realised. All the above constituents of milk fat are composed of
different proportions of carbon, hydrogen, and oxygen, but milk also
contains minute quantities of lecithin, a fat containing phosphorus in
addition