ent. The casein
is dissolved to some extent and the remainder so changed, that it
will remain in suspension for a long time in a finely divided form,
after the curd has been broken up. Such milk is sold under various
names at home and abroad. One of the authors (H) has found such
organisms in practically all milks examined. If raw milk is kept
warm (98 deg. to 100 deg. F.) in a stoppered bottle which is filled
full, the acidity will be found to increase slowly from day to day,
reaching a maximum in ten to fourteen days. If the milk is then
examined, it will be found to contain large numbers of an
acid-forming organism very different in appearance from the bacteria
causing the rapid souring of milk at ordinary temperatures. This
organism is very similar if not identical with the one found in the
Bulgarian milk to which the name _B. Bulgaricus_ has been given. The
use of the milk fermented by this organism has spread rapidly
because it is claimed by certain European bacteriologists that it
has a favorable effect on the health of people, especially those
suffering from intestinal troubles. It is not at all certain
that ordinary sour milk or butter milk will not have the same
effect; in fact in many of the fermented milks sold in Europe, _B.
Bulgaricus_ has not been found, but only the ordinary lactic acid
bacteria.

Several alcoholic drinks made from milk, such as kefir and koumiss,
have been originated among the nomadic tribes of Western Asia. Kefir
is prepared from cow's milk by adding the kefir ferment in the form
of grains which contain a number of kinds of bacteria and a yeast.
The acid-forming bacteria impart a sour taste to the fermented milk,
while the yeast forms carbon dioxide and about two per cent of
alcohol. If the milk is allowed to ferment in stoppered bottles, the
resulting product will be an acid effervescing drink, which is
claimed to be more easily digested than sweet milk. This drink is
used frequently in the treatment of invalids but it is improbable
that it is more easily digested than ordinary soured milk or butter
milk. The grains are removed from the fermented milk, and are then
added to a quantity of fresh milk, or they may be dried and kept for
future use. When needed again, they are soaked in water, then added
to the milk.

Koumiss is made in Russia from mare's milk and has much the same
composition as kefir. In America and Europe it is made from cow's
milk, by adding cane sugar and compress