1,600 grains, or 3·66 ounces of fatty matter which are present in the contents of 20 eggs may take the place of its ·944 ounce of fatty matter which are met with in the 2 pounds of bread and in the 4 pound of lean meat, and of the 16·320 ounces of starch and the other carbo-hydrates which are present in the 2 pounds of bread. For it may be fairly assumed that the properties of the nitrogenous and nonnitrogenous compounds are as properly balanced in the egg and milk, which are the two great typical forms of natural food, as they are in the artificial combination of bread and meat of which we are speaking. You may draw your own conclusions from the tables on the walls in which these facts are set forth.
C. I also find in these tables a curious correspondence as to the amount of mineral matter in the three cases under consideration. The proportion of mineral matter in the other constituents is as 1 to 18 in the egg, as 1 to 17 in milk, and as 1 to 17 in the case of meat and bread.
M. This correspondence may not be quite so close as it seems to be. In the case of the egg an uncertain amount of lime, probably a large amount, ought to be added, for the shell becomes thinner and thinner as the process of incubation goes on, in consequence of the solvent action of the phosphoric acid which is generated by the oxidization of the phosphorus in the contents of the egg. In the case of white bread (white bread was used in this experiment) the greater part of the mineral matter, which is lodged chiefly in the husks of the grain, is sifted out in the preparation of the flour from which white bread is made. The earthy matter of the shell is certainly necessary to the proper development of the bones of the chick, and in all probability the bones are not the only tissues which are in this case. A dog lives long and thrives when it is fed upon brown bread, but not when it is fed upon white bread. Scurvy also is a speedy consequence of living upon salt meat, which differs from fresh meat chiefly in the fact that the salts belonging to it have been transferred to the brine. If the body is to be properly nourished, the mineral matters which are contained in the different articles of food can not be excluded, that is evident. And if these different articles of food are to be properly digested, the common salt, in the food or taken along with the food, may have a very important work to do in addition, for without it it is not easy to see how the gastric juice could acquire that part of its acidity which depends upon the presence of hydrochloric acid.
C. I have always avoided fat and butter, on the supposition that they would make me bilious and stout. I also thought that they were specially indigestible. I knew that they were of great value as heat producers, as "elements of respiration," as fuel, and that the inhabitants of cold countries could not get on well without an abundant supply of them, but it never entered into my head to suppose that they might take the place of meat and bread.