Of all the elements of the income and outcome, the nitrogen, the carbon, and the free oxygen of respiration, are by far the most important. Since water is of use to the body for merely mechanical purposes, and not as food in the strict sense of the word, the hydrogen element becomes a dubious one; the sulphur of the proteids, and phosphorus of the fats, are insignificant in amount; while the saline matters stand on a wholly different footing from the other parts of the food, inasmuch as they are not sources of energy, and pass through the body with comparatively little change. The correct income will consist of so much nitrogen, carbon, hydrogen, oxygen, sulphur, phosphorus, saline matters, and water, contained in the proteids, fats, carbohydrates, salts, and water of the food, together with the oxygen absorbed by the lungs, skin, and alimentary canal. The outcome will consist of: 1. The respiratory products of the lungs, skin, and alimentary canal, consisting chiefly of carbonic acid and water, with small quantities of hydrogen and carburetted hydrogen, these two latter coming exclusively from the alimentary canal; 2. Perspiration, consisting chiefly of water and salts, with urea by the skin, and other organic constituents of sweat amounting to very little; 3. The urine, which contains practically all the nitrogen really excreted by the body, as well as a large quantity of saline matter and water. HEAT AND TEMPERATURE. The average temperature of the human body in those internal parts which are more accessible, as the mouth and rectum, is from 98.5° to 99.5° F. The chief circumstances by which the temperature of the healthy body is influenced are the following: Age. The average temperature of the new-born babe is only about 1° F. above that proper to the adult. In old age the temperature rises again, and approaches that of infancy. Sex. In the female slightly higher than in the male. Exercise. Active exercise raises the temperature of the body, through muscular contraction, etc. Climate and season. In passing from a temperate to a hot climate, the temperature of the human body rises slightly, rarely more than 2° to 3° F. In summer the temperature of the body is a little higher than in winter, 1/5° to 1/3° F. Cold alcoholic drinks depress the temperature 1/2° to 1°F. Warm alcoholic drinks, as well as warm tea and coffee, raise the temperature about 1/2° F. In disease, as in pneumonia and typhus, it occasionally rises as high as 106° or 107° F. In Asiatic cholera a thermometer placed in the mouth sometimes rises only to 77° or 79° F. The temperature maintained by mammalia of an active state of life averages 101° F. In birds, the average is as high as 107° F., the highest temperature, 111.25°, being in the species of the linnets, etc.