that the green
cheese, fresh from the press, would contain practically the same kind of
bacteria that are in the milk, but a study of cheese shows a peculiar
change in the character of the flora. In the first place, fresh cottage
cheese, made by the coagulation of the casein through the action of
acid, has a more diversified flora than cheese made with rennet, for the
reason, as given by Lafar,[186] that the fermentative process is farther
advanced.

When different varieties of cheese are made from milk in the same
locality, the germ content of even the ripened product has a marked
similarity, as is illustrated by Adametz's work[187] on Emmenthaler or
Swiss hard cheese, and Schweitzer Hauskaese, a soft variety. Of the nine
species of bacilli and cocci found in mature Emmenthaler, eight of them
were also present in ripened Hauskaese.

Different investigators have studied the bacterial flora of various
kinds of cheese, but as yet little comparative systematic work has been
done. Freudenreich[188] has determined the character and number of
bacteria in Emmenthaler cheese, and Russell[189] the same for cheddar
cheese. The same general law has also been noted in Canadian[190] and
English[191] cheese. At first a marked decrease in numbers is usually
noted, lasting for a day or two. This is followed by an enormous
increase, caused by the rapid growth of the lactic-acid type. The
development may reach scores of millions and often over a hundred
million organisms per gram. Synchronous with this increase, the
peptonizing and gas-producing bacteria gradually disappear. This rapid
development, which lasts only for a few weeks, is followed by a general
decline.

In the ripening of cheese a question arises as to whether the process
goes on throughout the entire mass of cheese, or whether it is more
active at or near the surface. In the case of many of the soft cheese,
such as Brie and limburger, bacterial and mold development is
exceedingly active on the exterior, and the enzyms secreted by these
organisms diffuse toward the interior. That such a condition occurs in
the hard type of cheese made with rennet is extremely improbable. Most
observers agree that in this type of cheese the ripening progresses
throughout the entire mass, although Adametz opposes this view and
considers that in Emmenthaler cheese the development of the specific
aroma-producing organism occurs in the superficial layers. Jensen has
shown, however, that the g