micro-organisms of a lactic yeast (Saccharomyces kefir Beyerinck and Freudenreich) and also the bacillus Bacterium caucasicum, which develop rapidly and split up the milk sugar into carbon dioxide, alcohol, and lactic acid. Small quantities of glycerine, acetic, succinic, and butyric acids are also formed, the casein and albumen being partly peptonised.26 Keffir becomes slightly effervescent in twenty-four hours, and in that time develops a small quantity of alcohol, but after three days the amount of alcohol and lactic acid is much increased.27 It has been determined that the fermentation of the milk is due to Saccharomyces kefir, and that the Lactobacillus Caucasicus does not take any part in the fermentation, a fact which seems to be supported by the capacity of ordinary keffir for starting the fermentation in fresh milk in the same manner as the keffir grains. The use of this beverage seems to be universal throughout the Caucasus, and travellers in these regions have frequently referred to it. Thus Freshfield28 states in one part of his book of travels as follows: