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 acid is developed in the process it is quite effervescent and may be regarded both as a food and a stimulant. It is sometimes prescribed by physicians in cases when the patient cannot retain other food.

Kefir is a similar preparation originally made in the Caucasus by a fermentation started by Kefir grains which contain both yeast and various bacteria. The dry Kefir grains are soaked, first in lukewarm water, later in lukewarm milk, for several days, until they develop so much gas as to float on the top. A couple of tablespoonfuls of the grains are then added to a quart of milk which is left to ferment at 70° F. under frequent stirring or shaking. When the fermentation is fully developed the grains are strained off and the milk is bottled and kept for 1 to 2 days at 60°. The grains may be used at once again in fresh milk, and when the manufacture is finished they may be dried and kept, to be used again another time.

Kefir grains of natural size; a, b and c dried; d, e and f soaked (Orla Jensen, Milk Bacteriology)