r of ripening.
The ripening is due to the action of organisms developing on the
surface, the by-products of which diffuse into the curd. If the
cheese are too large, the outer layers become overripe, while the
interior remains more or less unchanged, or insufficiently changed.
Soft cheese mature much more rapidly than hard cheese; consequently
they are short lived.

Although made from the same substance, milk, it is noteworthy that
there are over four hundred varieties of cheese produced. Most of
these find only a local market where made. Less than a dozen
varieties are to be regarded as general articles of commerce.

=Quality of milk.= In the making of butter there are a number of
processes that the maker can use when he finds himself obliged to
utilize poor milk. The milk can be pasteurized and the harmful
bacteria thus destroyed; desirable kinds can then be added in the
form of a pure-culture starter. Pasteurization also drives off some
of the volatile by-products of the first acid fermentation. By the
use of these means, the maker can prepare a very good product from
poor material.

In the making of most kinds of cheese, especially those of the
greatest commercial importance, the cheese maker can call to his
help no such aids, but must use the milk as it is brought to him. It
is possible to prepare certain kinds of soft cheese from pasteurized
milk that differ in no essential point from the same cheese made
from raw milk. Hard cheese are also made from pasteurized milk, but
in most cases such cheese differ, especially in the degree of
flavor, from that made from unheated milk. It is quite probable
that, as the factors concerned in the ripening of cheese become
better known, methods will be evolved for the successful production
of many kinds of cheese from pasteurized milk.

It has been shown that the quality of milk is almost wholly
dependent upon the number and kinds of bacteria it contains. These
bacteria pass into the cheese, and there produce the same products
as they would have done in the milk itself. In butter making,
practically all processes are under the control of the maker, until
the product is ready for the market; but cheese, on the other hand,
passes through a complicated series of changes after it has left the
maker's control. During the manipulation of the milk and the curd in
the vat, he can exert some influence on the quality of the product,
but he is much more dependent on the quality of th