Due Proportion of Animal and Vegetable Food.-It has been taken for granted thus far that the mixed fare, which has met the approval of so many generations of men, is that which is most in accordance with reason. But there are physiologists who argue that our teeth resemble those of the vegetable-feeding apes more than those of any other class of animal, and that, therefore, our most appropriate food must be of the fruits of the earth.1 And if we were devoid of the intelligence which enables us to fit food for digestion by cookery, it is probable no diet would suit us better. But our reason must not be left out of account, and it is surely quite as natural for a man to cook and eat everything that contains in a convenient form starch, fat, albumen, fibre, and phosphorus, as it is for a monkey to eat nuts or an ox grass. The human race is naturally omnivorous.

Moreover, man is able not only to develop his highest faculties and perform all his duties on any form of digestive aliment, but he is able also very much to diminish the requisite quantities by a due admixture. The diet which supplies the demand most accurately will be the most economical in the highest sense; and that this diet is a mixed one can be shown by the following method of calculation: We can measure by experiment the ultimate elements of all that is thrown off from the body as the result of vital decomposition-the ashes, the smoke, and the gases, which the fire of life produces; and thus we can lay down a rule for the minimum quantity of those elements which the daily food must contain to keep up the standard weight. If the diet be such as to make it necessary to eat too much of one element in order to secure a sufficient amount of another, there is a waste, and the digestive viscera are burdened with a useless load. But there is no single article procurable for the food of the adult population which presents the exact proportion of elements required by an adult, and therefore no single article alone can supply human wants without waste.

As an example, apply this reckoning to the elements carbon and nitrogen, which constitute the main bulk of solids in our food and in our bodies. Suppose a gang of 100 healthy prisoners to excrete, in the shape of breathed air and evacuations, 71 1/2 pounds of carbon and 4 1/4 pounds of nitrogen (which is pretty nearly the actual amount of those elements in the dried solids of the secreta, as estimated by current physiological works). Both nitrogen and carbon to that extent must of course be supplied in the food. Now, if you fed them on bread only, there would be wanted daily at least 380 pounds of it to sustain them alive long, for it takes that weight to yield the 4 1/4 pounds of nitrogen daily excreted; while in the 380 pounds of bread there are 128 1/2 pounds of carbon, which is 57 pounds above the needful quantity of that substance.1

1 Milne-Edwards, " Cours de Physiologie," volume vi., page 198.

If, on the other hand, the bread were replaced by a purely animal diet, there would have to be found 354 pounds of lean meat in order to give the 71 1/2 pounds of carbon; and thus there would be wasted 105 pounds of nitrogen contained in the meat, over and above the 4 1/2 pounds really required to prevent emaciation.2

In the first case, each man would be eating about 4 pounds of bread, in the second, 3 1/2 pounds of meat, per diem. If he ate less, he would lose his strength. The first would carry about with him a quantity of starch, and the last a quantity of albuminous matter, not wanted for nutrition, and would burden the system with a useless mass very liable to decompose and become noxious.

When work is undertaken, much more is actually wanted. According to Mr. Vizetelly, the laborer in a Spanish vineyard consumes daily between 8 and 9 pounds of vegetable food, consisting of bread, onion-porridge, and grapes.3 And when animal food alone is taken, as in the case of the Esquimaux, 20 pounds of it a day is the usual allowance.

Now, if a mixed dietary be adopted for the gang of 100 prisoners before mentioned, 200 pounds of farinaceous food, with 56 pounds of animal muscle, would fulfill the requirements of the case; 2 pounds of bread and a little more than 1/2 pound of meat a head would be enough, under ordinary circumstances, for each man's daily food.

1 Dr. Letheby's analysis gives 8.1 per cent, of nitrogenous matter to bread (" Lectures on Food," page 6). Of this one-seventh is nitrogen, Boussingault's analysis of gluten giving 14.60 per cent. (" Annales de Chim. et Phys.," lxiii., 229). M. Payen makes the proportion of nitrogen to carbon in bread as 1 to 30.

2 The proportion of nitrogen to carbon in albumen is as 1 to 3 1/2 (15.5 to 53.5 by Mulder's analysis, quoted in Lehmann, " Phys. Chemie," i., 343). In red meat there is 74 per cent of water (ditto, iii., 96).

3 " Facts about Sherry," chapter i (Introductory. On Cleaning Ranges, Stoves, And Kitchen Utensils. Lesson First. How To Clean A Kitchen Range Or Stove)., 1876, and Sir John Ross's "Second Voyage for the Discovery of the Northwest Passage," page 413.