MILK ( AS. meole, meolue, loth. mihrks, onc. Ger. MUNI; connected with AS. nucleon, Ott(;. mrlehan, (7er. me/ken, Lat. mulgerc. (1k. dila-yaw, onuggrin, °Church Slay. mirth, Lith. mifsti, to milk, Ski. mar).
?flora:, to rub oil). The liquid svereted the mammary glands of all mammals. and used primarily to nourish their young. From the earliest time it has been esteemed an portant and necessary article of food, and many hidden virtues were ascribed to it by the ancients. Its exact composition continual long unknown, and until the beginning of the seventeenth century fat, casein, and whey were the only constituents recognized. In the early part of the eighteenth century Leeuwenhoeck discovered the microscopical characteristics of milk, and about the Same time Boerhaave made a qualitative examination. The first quantitative analysis of milk recorded was made in 1737 by Geoffrey, who determined with considerable accu racy the casein, milk sugar, and mineral matter.
Woman's milk contains 87.4 per cent. of water and 12.6 per cent. of solids, the latter including 3.8 per cent. of fat, 1.0 per cent. of casein, 1.3 per cent. of albumin. 6.2 per cent. of milk sugar, and 0.3 per cent. of ash (mineral matter left after burning). The milk from different animals varies considerably in composition, as shown in the following table: minus the water are designated total solids. The
proportion of total solids is a general indication ot the riehness of the milk. Among the solids the chief importance attaches to the fat. First, it is the measure of the value of milk for butter-mak ing, and to a very great extent for cheese-making also; second, it is the constituent which more than any other gives milk its appearance of rich Doss; third, it fluctuates more widely than any other constituent. Milk fat is a familiar sub stance in the form of butter, which contains about 85 per cent. of fat, some water, salt, and casein. The fat in milk is in the form of minute globules held in suspension, and on standing it rises to the surface as cream (q.v.), which con tains some of the other constituents in smaller proportion. The globules may he readily seen by The above are general averages of a greater or less number of analyses, depending upon the kind of milk animal, each kind of which gives milk that varies more o• less with the individual as well as with the species. There is. further more, some difficulty in arriving at a general average for any kind of mammal, since normal milk is obtained with difficulty from animals unaccustomed to being milked.