organism, such as _Bacillus keffir_, is indispensable. [Illustration: FIG. 12—_Streptococcus lacticus_ (Grotenfeldt) growing on lactose-agar, stained by Gram's method. ( ✕ 900 diams.)] _Diseases of Keffir Grains._—According to the age and the previous treatment to which keffir grains have been subjected, the vitality of one or more of the organisms constituting the grain may have been impaired. The results of Freudenreich have shown that _Saccharomyces keffir_ and _Streptococcus a_ are unable to withstand desiccation for more than a few days, and this is sufficient to account for the frequent failures to obtain normal keffir from the grain. Further, grains succumb to a mucilaginous disease; the cavities become filled with a slimy fluid, and the grains are covered with mucilaginous matter. They lose their elasticity and become brittle or mealy, but large grains appear to be more subject to this fault than do the small ones. Such grains should be disinfected by immersion for a short time in two per cent. salicylic acid solution, followed by drying in the sun, whereby they are completely regenerated. Another disease consists in the predominance of certain butyric acid bacteria which impart an unpleasant rancid taste to the keffir (Podowyssozki). This is generally attributed to the use of rich milk, or too high a temperature during preparation. _Koumiss._—Another product of the combined action of lactic acid and alcohol-producing organisms is called koumiss, kumys, milk-wine, lac fermentation, or vinum lactis. In the steppes of Southern Russia and Asia, as we have seen,[59] it is prepared chiefly from mares' milk, but occasionally from that of camels and jennets. The name is said to be derived from that of a tribe mentioned by Xenophon and Pliny, viz., the Kumanen, by whom its preparation was practised. After the war with the Tartars in 1215 its use was adopted by the latter people, and eventually spread to the Turkomanen, Kalmucks, Khirgiz, Mongolians, etc. Rubruck, in 1253, records the use of a fermented drink—kosmos—prepared from mares' milk, and about the same time Marco Polo mentions the occurrence of a milk-wine, chumis or chemius, among the Tartars. The fact that the Tartars were seldom ill, and were almost invariably free from lung troubles, led to an influx of visitors from surrounding countries, until finally its use spread to Russia, Austria, and Germany. At the present time the best koumiss is that produced in the province of Orenburg; but specially equipped koumiss establishments, under the control of physicians, exist in Odessa, Samara, Ufa in the Urals, and other districts. The curative properties of koumiss have long been recognised and its use is indicated in cases of indigestion, chlorosis, scurvy, tuberculosis, etc.