MILK, the fluid secreted by all female mammals for the nourishment of their young. As an alimentary substance, it may be regarded as a perfect food. It consists essentially of a solution of sugar, albuminous and saline matter, and holds in suspension a certain pro portion of fat in the form of very mi nute globules. Mare's milk contains a larger proportion of sugar, while that of the ewe is very much richer in al buminous and fatty constituents, the milk of the cow having its composition more evenly adjusted. Milk sponta neously ferments, the sugar being con verted into lactic acid, alcohol, and car bonic acid gas. When an artificial fer ment has been used, a larger proportion of alcohol is generated, and the milk is converted into a product to which the name of koumiss has been given. The chief adulterant added to milk is water; but sugar, carbonate of soda, salt, salicylic acid, and borax are also occa sionally used. Condensed milk consists
of cow's or goat's milk which has been evaporated by the aid of steam pipes or a vacuum pan.
In human physiology, milk is the se cretion of the mammary glands, whose activity begins at delivery, and continues for a period of nine months as a rule, but, if encouraged, may persist for a longer time. The fluid secreted contains all that is requisite for the nourishment and development of the child. The first milk secreted is colostrum; it acts as a natural purgative to the child.
Municipal and State governments in the U. S. A. for many years have worked for a supply of pure, cheap milk. After the World War the authorities of New York State and City were especially active in regulating the milk industry, and keeping down the price.