Ranke1 describes experiments on himself (weight = 73 kilograms) during the hottest months of summer weather in Munich, at which time he partook of an ample diet, rich in protein (135 grams), containing 3300 calories - a diet which he had enjoyed during the preceding winter. He had to force himself to eat. He was first attacked by catarrh of the stomach, from which he recovered by dieting, and subsequently became infected by diphtheria. He had formerly suffered from catarrh of the stomach while residing in the tropics. The excess of food, and especially of protein, threw an unnecessary burden upon the heat-regulating apparatus which would not have taken place had the dictates of the appetite been allowed full sway and had the ration voluntarily been reduced.

From the knowledge at hand there appears to be no strongly substantiated argument why that portion of mankind living in a cool climate should not follow the general custom of taking 100 grams of protein, more or less, in moderate accordance with the dictates of their appetites. Everyone knows that excessive ingestion of highly flavored meats results in jaded appetite, an automatic signal of excess.

A similar excess of food when given to dogs results in vomiting. Rubner1 says that many years of experience with dogs leads him to believe that appetite and capacity for digestion and absorption depend on the dog's requirement for energy in his given state of nutrition. A diet which a dog will greedily devour when in a room at a temperature of o° he will in part refuse when at a temperature of 330.

1 Ranke: "Zeitschrift fur Biologie," 1900, xl, 299. 2 Rubner: "Energiegesetze," 1902, p. 83.

Evvard1 writes: "When the appetite is given full control of what shall be eaten it is surprising to note how pigs naturally select the specific feeds which swine herdsmen have long since approved of as the best, and, what is equally surprising, the pigs show a marked avoidance of those feeds usually considered as ill adapted to swine".

While the protein quantity in the diet may vary within wide limits with the taste, the purse, or the fad of the individual, the quantity of energy required by the organism is a remarkably constant factor, being 3 5 calories per kilogram of body weight in the average man doing light work on a mixed diet. Comparatively little of this energy is furnished by protein.

In a fasting individual protein furnishes 13 and fat 87 per cent, of the total heat given off from the body.

In Voit's medium mixed diet, designed for a laboring man, the 118 grams of protein furnish about 15 per cent, of the total of 3055 calories.

In such an experiment as Siven's, mentioned on page 336, which represents a very low level of nitrogen equilibrium, the 25 grams of protein ingested furnished 100 calories out of 2717 ingested in the food, or 3.6 per cent. However, since the total metabolism was measured as 2082 calories, the protein furnished approximately 5 per cent, of this energy.

Chittenden2 gives a dietary containing 50 grams of protein and 2500 calories as sufficient for a soldier at work. This allows 8 per cent, of the total energy in protein. These data may be thus summarized:

1 Evvard: "Proceedings of the Iowa Academy of Science," 1915, xxii, 400.

2 Chittenden: Loc. cit., p. 254.

The energy other than that contained in protein may be given as carbohydrates or as fat. Voit allows a laborer 500 grams of starch (2050 calories, or 67 per cent, of the total) as the quantity which the intestinal canal may readily digest, and adds 56 grams of fat (521 calories, or 17 per cent, of the total) to the diet.

It has already been observed that half the energy may be given in fat and half in carbohydrates without affecting the carbohydrate power of economy over the protein metabolism (see p. 270).

This part of the subject really becomes a mere matter of calculation of the requirement of the resting organism, and the addition thereto of sufficient energy to accomplish the mechanical work.

How this is done has already been set forth in another chapter. A bicyclist riding for sixteen hours may have a metabolism amounting to 9000 calories daily, and the average ration of a Maine lumberman may rise to a value of 8000 calories. Champion wrestlers in a world's contest1 may ingest daily during their periods of effort diets containing protein 217.9 grams(35.1 grams of N); fat, 259.5 grams; carbohydrates, 431 grams; together, 5070 calories; or protein, 182.2 grams (29.2 grams N); fat, 204.6 grams; carbohydrates, 392.3 grams; together, 4254 calories. Much cream was taken by these last-named individuals.

Chittenden2 has fallen into error in the commendation of 2500 to 2600 calories as an ample diet for a soldier at drill. For himself, pursuing a sedentary life, Chittenden prescribes 2000 calories, or 35 per kilogram, while Mendel requires 2448 calories, or 35.3 calories per kilogram. These are entirely normal values for people at light work. In the earliest calculations of Voit, in 1866, it was shown that a man of 70 kilograms on a medium mixed diet produced 2400 calories, or 34.3 calories per kilogram; and Rubner allows 2445 calories to men of 70 kilograms weight engaged in occupations involving light muscular work - such men as writers, draughtsmen, tailors, physicians, etc. But the soldiers under Chittenden were put for two hours in the gymnasium, then apparently drilled for one hour, and walked another hour. This physical work requires increased energy from metabolism. It has been shown that to walk 2.7 miles in an hour on a level road requires an increased metabolism of 159.2 calories in a man weighing 70 kilograms. If a soldier during four hours actually expended this equivalent mechanical energy in excess of the amount of Professor Mendel in his laboratory, then his metabolism would be larger than Professor Mendel's by 637 calories, or he would have a total metabolism of 3085.

1 Lavonius: "Skan. Archiv fur Physiologie," 1905, xvii, 196. 2 Chittenden: Loc. cit., p. 254.