Page:Pure milk - a lecture delivered in the lecture room of the exhibition, July 30th, 1884 (IA b28525140).pdf/14

 a large proportion of the milk sugar present being deposited at a certain stage of the boiling, in an imperfect crystalline form, while the other part remains in solution. The polarization differs considerably from the polarization of any other known sugar. All these different points mark it out as a peculiar sugar. There is a good deal yet to be done in investigating the chemistry of sugar of milk, and it appears very probable that at some future time, further investigation may show that in reality what we look upon as a simple sugar, consists of different substances mixed together in proportions which are at present unknown. Sugar of milk is important in another way, as it forms the great point of difference between human milk and cow’s milk.

Human milk contains a larger proportion of sugar than cow’s milk, and less fat, caseine, albumen, and ash. It is from this that the formula generally adopted in the manufacture of artificial human milk is obtained; cow’s milk is diluted with water, and then milk sugar added; by this means we obtain a liquid which assimilates somewhat closely in chemical composition to true human milk.

This term includes a variety of salts which, physiologically considered, are of very great importance in the composition of milk. It is absolutely essential for the formation of bone and muscle that a growing child, or for the matter of that an adult, should be supplied with certain phosphatic substances, lime salts, etc. Milk contains these ingredients in the right proportions to form the bone and muscle of a child.

We now come to the water, the last and largest constituent'.

Water, of course, strictly speaking has no real dietetic value, and yet without water milk itself would be useless as food, because it is essential that the valuable food ingredients of which we have already been speaking should be dissolved or emulsified, so as to be in a suitable form