The milk of the cow differs a good deal from human milk, and where the former is used for the feeding of children it is usual to add milk sugar to it, and otherwise alter it to bring its composition more in harmony with the human article. The high concentration of the milk of the reindeer and the whale is noteworthy. Perhaps this may be due to the low temperature conditions in which these animals live, necessitating strong nutriment to enable their young to make proper progress in growth and development. On the other hand, the milk of the ass is poor in quality, and probably on this account it is more readily assimilated by those of weak digestion, to whom it is sometimes recommended. Goats' milk is richer than either cow or human milk, and its nourishing properties are well known. The goat is usually free from tuberculosis and other diseases which affect the cow, and its milk is therefore a very safe article to use.
_The Analysis of Milk._—While the analysis of milk can only be made by a competent chemist, there are a number of simple tests and observations by which any intelligent person can obtain a fair idea of its quality. The taste and smell afford some guide, as also the general appearance. To judge of the latter, place some of the milk in a tumbler or other clear glass vessel. If the milk is of good quality it will be quite homogeneous and opaque. Any flocculent matter indicates either disease in the cow or that the milk is old and bacteria have multiplied in it and altered its composition. When the milk has stood long enough for the cream to rise freely, the latter should form a perfectly homogeneous and strongly defined layer on the top. The quantity of cream may be measured in a creamometer, which consists of a small glass cylinder graduated at the top (Fig. 5). It is filled with milk to the top graduation line, and when the cream has risen, the percentage quantity of the latter which has separated can be taken off.
The colour should be like that of porcelain, but, as already stated, it is a common thing for the dairyman to add a small quantity of anatto or an aniline dye of a similar shade, to give the milk a rich creamy tint. If the milk is of a reddish colour this may be caused by blood from the udder, although certain foods, such as beets, mangels, and carrots sometimes give a similar tint. The milk given by cows immediately after calving is called "colostrum" or "biestings," and is of a yellow or yellow-brown colour. It is much thicker than ordinary milk, and coagulates in boiling.