Even at city prices milk might well be substituted to a certain extent for other proteid foods. The habit of many people of using milk simply as a beverage in addition to the food required, is perhaps responsible for the fact that many people find milk indigestible; the difficulty lies not with the milk but with the overabundance of food. An experiment was tried at the Maine Agricultural College on the effect of a limited and an unlimited amount of milk at the University boarding house. These experiments are reported in the Government Bulletin called Milk as Food, and the following conclusions are drawn:
"First, the dietaries in which milk was more abundantly supplied was somewhat less costly than the others, and at the same time was fully as acceptable. Second, the increased consumption of milk had the effect of materially increasing the proportion of protein in the diet. Third, the milk actually supplied the place of other food materials, and did not, as many suppose, simply furnish an additional amount of food without diminishing the quantity of other materials. Fourth, the results indicate that milk should not be regarded as a luxury, but as an economical article of diet which families of moderate income may freely purchase as a probable means of improving the character of the diet and of cheapening the cost of the supply of animal food".
We may conclude that while it would not be economical to obtain our total food supply from milk, it is good economy to use it freely in connection with other foods to furnish part of the proteid of the diet.
The digestibility of milk varies very much with the method in which it is taken. If a small amount of liquid rennet or of the junket tablets so commonly found in the market, be added to a portion of warm milk, a thick clot forms. This is similar to the process that takes place in the stomach after milk has been swallowed. Milk properly, then, so far as its digestion is concerned, is a solid rather than a liquid food. Its digestibility depends largely upon the way in which this clot is formed. If the milk be swallowed rapidly, so that the rennin acts upon a large mass at once, one large clot is formed. If, on the other hand, the milk be sipped slowly, or eaten from a spoon, the action is slower and the curd is broken.
The same result in a more marked degree is obtained by the addition of certain substances, such as lime-water, to the milk; or by the mixing of the milk with bread, as is done in eating bread and milk. Some people who cannot use milk in its ordinary form have found that they could digest it without difficulty if a cracker were rolled into fine crumbs and stirred into the milk. The digestive juices that would act slowly upon a large mass of curd, act readily upon the same amount when it is broken into small clots.