Koumiss (spelt also kumyss) is a fermented liquor made originally by the Tartars from mares' milk; a somewhat similar liquor, called lebau or yaourt, is made from cows' milk by the Arabians and Turks; it is also prepared by the Russians under the name of kef. To prepare it, the milk is diluted with a little water, then placed in bags made of hides, and shaken till the cream is thrown up; it is then placed in earthen vessels and kept in a warm place until fermentation takes place. To hasten this, a little koumiss is added from a previous fermentation. The liquid is frequently well stirred to incorporate the curd and fat, and must be shaken before being drunk. The process is a true fermentation, the milk sugar being destroyed by a peculiar ferment with the production of lactic acid, alcohol, and carbonic acid. The liquid is said to have an agreeable sourish taste, and is sometimes recommended, though it is rarely seen, in England. One of the few means of getting the ferment in this country is to shake the milk in a bladder or to add some rennet. According to the American Druggist, koumiss commonly is made in America by adding yeast to cows' milk and then fermenting.

The best results are, however, obtained from the use of mares' milk, this being the basic ingredient of the original Russian koumiss. Mares' milk is less rich in casein and fatty matter than cows' milk, and is therefore more easy of digestion. In the United States of America cows' milk is used always, and generally it answers the purpose well, but it is better to dilute the milk with water to reduce the percentage of casein, etc. Mares" milk contains 8.75 per cent, of milk sugar, cows' milk only 5'35; therefore it is necessary to add sugar to the preparation when made from cows' milk. The following-recipe has been found to answer well. Dissolve 3oz. of milk sugar in 32 oz. of water, and add the solution to 95 oz. of milk; rub together 1/3 oz. of compressed yeast and 2 1/2 oz. of brown sugar in a mortar with a little of the mixture, and then strain into the other portion. Strong bottles are essential, champagne bottles being frequently used, and the corks should fit very tightly and be wired down; if the cork does not fit properly, the carbonic acid gas as formed will escape and leave a worthless preparation.

The koumiss must be kept at a moderate temperature, and to ensure it being properly finished the bottles containing it should be gently shaken each day for about ten minutes to prevent the clotting of the casein. It is well to take the precaution of rolling a cloth round the bottle during the shaking process, as the amount of gas generated is great, and should the bottle be of thin glass or contain a flaw it may burst. Some few days elapse before the fermentation passes into the acid stage, and when this has taken place the preparation is much thicker. It is then in the proper condition for allaying sickness, being retained by the stomach when almost everything else is rejected. A fairly good quantity of koumiss may be prepared in a small way in the following manner. Fill a quart champagne bottle to the neck with pure cows' milk, add two tablespoonfuls of white sugar dissolved in a little warm water, and a very small quantity of compressed yeast. Then securely fasten the cork in the bottle and shake the mixture well; place it in a room having a temperature of from 70° to 80° F. for six hours, and finally in an ice box for about twelve hours, and it then should be ready for use.