The heat of the body is produced by the action of the lungs, which uses up the heat-producing food, as action of muscle or brain consumes the muscle-making material. The former is non-nitrogenous; the latter nitrogenous. Foods may be divided into three groups: the nitrogenous, in which nitrogen is the chief element, and which feed muscle only; the non-nitro-genous, chiefly carbon, which produce heat only; and those in which both are united.

It has been proved by chemical analysis that the body requires four to five ounces for heat to one for muscle, and this gives us the key to the proper proportion of the elements in food, varying slightly, of course, with seasons, climates, occupation, and conditions.

The substance richest in nitrogen, the muscle-making element, is albumen, found in its most perfect form in the white of an egg. The lean or red parts of beef, mutton, venison, and chicken contain nearly as great a percentage - about fifteen per cent. The curd of milk, also, contains a large percentage, as well as grain, pease, and beans. If muscles only were to he ted, these would be nearly perfect foods, hut for one ounce that goes to muscle, five ounces must go to heat, and this culls for carbon.

The carbon needed to keep up the bodily heat comes chiefly from starch, which is abundant in the vegetable kingdom. Grate a potato and wash in a succession of waters, allowing the sediment to deposit each time, and a floury substance will appear, perfectly white, and dry and crispy to the touch. This is starch, and consists of round grains, too small to be seen by the eye. One-half of the bulk of dry starch is carbon; the remainder is oxygen and hydrogen in exactly the proportion as in water; and in that wonderful laboratory, the stomach, the carbon is eliminated from the starch, and the oxygen and hydrogen combine to form water.

The starch made from wheat is seldom used as food. Sago, Tapioca, and arrowroot, so much used for puddings, are almost pure starch, with slight coloring matter taken from the material. Corn starch is less agreeable in flavor, and makes a less firm jelly when cooked. These dessert dishes are easily digested, and contribute carbon, but do not feed muscle, except as they are combined with milk, eggs, etc., in cooking, which contain a little nitrogen and a good deal of carbon. This food, then, is not adapted to a working man or to growing children, who need to have their muscles fed. For persons of sedentary habits, especially for the aged, whose feebler respiration needs a large supply of carbon to keep up heat, they are valuable because easily digested. For others they are of value only to supplement muscle-making food as a dessert.

The following table (Prof. Yeomans) gives the proportion of starch in common grains:

Per Cent Starch.

Bice Flour,

84 to 85

Indian Meal,

77 to 80

Oat Meal, .

70 to 80

Wheat Flour,

39 to 77

Per Cent Starch.

Barley Flour,, .

67 to 70

Rye Flour, .

50 to 61

Buckwheat,

52

Pease and Beans.

42 to 43

Potatoes (75 per cent water) 13 to 15. . The large variation in wheat flour is due to processes of grinding. Varieties of wheat only vary about five per cent, but the old process of making fine white flour, used only the middle or starchy parts of the kernel, rejecting the gluten (nitrogenous and muscle-feeding). The whitest and highest-priced flour was, therefore, least nourishing, containing the largest per cent of starch. Modern invention has, however, reversed this, and the best "new process" flour contains the largest proportion of gluten. The old argument in favor of Graham, that it contained a larger proportion of nitrogen, and better supplied the body with muscle-making material, no longer holds good. Analysis shows that the best "new process" flour and Graham are almost identical in these elements. The only advantage left for Graham is the action of the coarser particles of bran (the outer shell and indigestible) on the coatings of the stomach, which is often salutary, but sometimes injurious to the delicate membranes. When flour and bread made from it contains one part nitrogen to four of carbon, it is nearly perfect food, and will sustain life.

The substance which is of next importance in supplying carbon to the body is oil (which is chiefly carbon). The oils used for food are butter, lard, and fat of beef. Other oils, used sometimes in cooking, are nearly identical with these. They contain about eighty per cent of carbon, butter having the least. In grains, oil varies, being nine per cent in corn meal, six in oatmeal, three and a half in rye, and one to two in wheat. Oils and starch serve the same purpose in the digestive process; both are useful to supply carbon; neither nourish muscle. Starch is easy of digestion, requiring one hour, while butter is converted into chyme in three and one-half, mutton-fat in four and a half, and beef-fat in five and a half hours. This furnishes the best of reasons why fats should be sparingly used, especially in warm and moderate weather, when a sufficient supply of carbon is easily secured from vegetable foods. Besides, it is a well established fact that excessive use of fats in cooking cause an excessive secretion of bile, and this, in turn, causes a sensation like hunger and an increase of saliva. This is mistaken for real hunger. More food is taken, and indigestion and, later, dyspepsia result. An eminent authority says: "I believe it will be found the offending ingredient in nine-tenths of the dishes that disturb weak stomachs." Dyspeptics need to reject not only foods in which fats are mixed, but those in which they are a natural element, such as the yolk of eggs, liver, milk, rich cheese, etc. Yolks contain twenty-eight per cent of oil, and milk over three per cent. One condition only calls for the use of fats in daily diet: Long-continued exposure to excessive cold. One pound of fat furnishes as much carbon as two and four-tenths pounds of starch, or seven and seven-tenths pounds lean meat. When the moisture of the breath is converted to ice and freezes on the beard, the air has no watery vapor and is nearly pure, containing a large per cent of oxygen. To meet this in the lungs requires abundant carbon, and oils furnish this most readily.