The data given below, which are derived from Bauer, exhibit the balance of income of food and output of waste of the body under different conditions of rest and activity.

The following data are quoted by Yeo:

"According to Dujardin-Beaumetz, a man loses, in connection with the processes of nutrition, nitrogen, carbon, water, and salts. In twenty-four hours these losses [for an adult man at moderate labour], on an average, amount to 20 grammes (300 grains) of nitrogen, 310 grammes (4,650 grains) of carbon, 30 grammes (450 grains) of salts, and 3 litres (about 6 pints) of water. The chief part of the nitrogen (14.5 grammes) passes away in the urine in the form of urea and uric acid, and the remainder (5.5 grammes) in the faeces, perspiration, and mucous discharges. Of the carbon, 350 grammes are consumed in the lungs, 45 grammes are eliminated by the kidneys, and 15 grammes in the other secretions. The water passes off by the skin, lungs, kidneys, and bowels. A man's food must contain the elements necessary to repair these incessant losses.

"The 20 grammes of nitrogen represent 124 grammes of dry proteid matters, and as these contain 64 grammes of carbon, on subtracting the 64 grammes from the 300 grammes necessary for nutrition there remain 236 of carbon to be derived from starch substances or from fats".

When waste matter has accumulated in the system its elimination may be assisted in various ways, as follows:

1. Through active exercise, which produces more complete oxidation and the formation of a larger proportion of water and carbon dioxide.

2. By diuretics, large draughts of saline waters, and occasional doses of saline cathartics.

3. By Turkish baths, which increase the elimination from the skin.