anisms and the use of pure cultures of lactic acid bacteria in their
relation to butter and cheese making, a new sphere in micro-biology has
been disclosed by the study of the effects caused by the combined growth
of two or more different classes of organisms in milk and the consequent
production of lactic, alcoholic, and gaseous fermentations. The
simultaneous occurrence of these fermentative changes is responsible for
the formation of such beverages as keffir, koumiss, milk-wine, etc. It
has therefore become essential, in connection with the study of new
developments in the milk industry, that we should make a more intimate
acquaintance with the bacteriology of the ferments involved.

_Keffir_ (_kephir_, _kifyr_, _kiafyr_, _kephor_, _kyppe_) is the name
given to an acid, slightly alcoholic drink, which for many centuries has
been prepared by the nomadic tribes in the Caucasus. The characteristic
fermentation is induced by the addition of so-called keffir grains.
These are yellow or golden-yellow, warty, and furrowed flakes or
nodules, the former varying in size from that of a rice grain to that of
a bean, while the latter are often about an inch across and one eighth
of an inch thick. Bearing in mind the fact that the preparation of
keffir has been carried on for many centuries, it is not surprising that
the origin of these grains should be surrounded by myths.

The belief is prevalent among the Mohammedan tribes of the Caucasus that
keffir grains were, in the first instance, presented by Allah, as a sign
of immortality, to one preferred tribe. Others hold that, in past ages,
they were found by shepherds growing on a shrub in the Caucasian
highlands; while, according to Skolotowski,[47] they were originally
found adhering to the walls of an oaken vessel used for the preparation
of airam. This is a soured milk beverage similar to keffir, but
possessing a weaker alcoholic fermentation, and prepared from goats'
milk by the addition of pieces of calf's stomach. This would undoubtedly
serve to introduce various species of lactic acid bacteria, and will be
referred to in the portion dealing with soured milks. Keffir is prepared
by the Caucasians from cows', sheep's, or goats' milk, and the operation
is carried on in large leathern tubes or bottles. After the addition of
the grains or seeds to the milk the vessel is placed in a cool chamber,
and the fermentation is allowed to proceed for one or two days, by the
end of which