most of the fat. Because of the fat it contains, the cream is yellower
in color than the milk underneath. If the cream is beaten, or churned,
these fat particles will adhere in a mass, advantage of this fact being
taken in the making of butter.

10. CARBOHYDRATE IN MILK.--The carbohydrate contained in milk is in the
form of sugar called _lactose_. It is unlike other sugars in that it is
not very sweet and does not disagree with most persons nor upset their
digestion. For this reason, it is often given to children, invalids, and
persons who have digestive disturbances. However, it is like other
carbohydrates in that in solution it ferments. The result of the
fermentation in this case is the production of _lactic acid_, which
makes the milk sour. With the fat, lactose makes up the bulk of the
energy-producing material of milk, and while this is important it is
only secondary when compared to the tissue-building power of the protein
and minerals. Besides being an important part of milk itself, lactose is
a valuable by-product in the manufacture of cheese. After being taken
from _whey_, which is the clear, straw-colored liquid that remains when
the curd, or coagulated portion, is completely removed from the milk,
the lactose is refined and sold in the form of a powder that is used for
various kinds of infant and invalid feeding.

11. MINERAL MATTER IN MILK.--Considerable quantities of mineral salts,
which are chiefly _lime_, _potash_, and _phosphates_, are found in milk.
As has already been pointed out, these are important in the building of
bone and hard tissue in the body, but in addition they help to keep the
fluids of the body in the right condition. Because of the work they do,
these mineral salts are necessary in the building of the bodies of
growing children, and are useful for repair and the regulation of the
body processes in adults. In cheese, butter, and cream, which are the