The distance between opposite points of the curved line represents the total metabolism at a particular temperature.

The principles laid down here regarding the lower animals apply equally to man. He too may come under the influence of chemical regulation, although he constantly endeavors to maintain the surface of his skin at a tropical temperature through the use of clothes. His heat loss may, like the dog's, be more difficult if he be covered with a thick layer of fat, and his metabolism is also influenced by atmospheric conditions of moisture, wind, and temperature.

One of the earliest demonstrations of the action of chemical regulation was afforded by Voit, who placed a fasting man weighing 70 kilograms in the Pettenkofer-Voit respiration apparatus and determined the carbon dioxid and nitrogen output for six hours. The person accustomed himself to the given temperature by staying under its influence for some time previous to the commencement of the experiment. In the cold experiments the ventilating air was derived from the winter atmosphere. For the warm periods the air was artificially heated. The subject of the experiment wore clothing which was comfortable in the usual warm atmosphere of the laboratory. Voit1 gives the following results:

Effect Of Temperature On The Metabolism Of A Fasting Man. Six-Hour Periods

The nitrogen elimination remains unaffected by temper-ature. At the ordinary room temperature there scarcely seems to be any increase in carbon dioxid output, but at the lower temperatures the quantity of the fat metabolism is markedly increased, as shown by the rise of carbon dioxid elimination. The individual sat quietly in a chair, but at a temperature of 4.40 C. could not prevent himself from shivering.

1 Voit: "Zeitschrift fur Biologie," 1878, xiv, 80.

The whole effect of the chemical regulation in man has been attributed by Johansson1 and also by Sjostrom2 to the additional metabolism due to shivering. Voit did not believe that this could be the cause, nor that the increased respiratory activity could account for the rise in metabolism. Voit belived the increase to be a reflex stimulus of cold on the skin which raised the power of the muscle cells to metabolize.

Voit's views have been confirmed in Rubner's laboratrny3 in the following series of expriments on a man:

In this experiment there was no shivering at a temperature of 150, and yet the metabolism increased from what it was at 23°.

It has also been shown that cool baths and winds increase the metabolism, which must be effected through the chemical regulation. Lefevre4 states that a man who has been inured to it may sit naked for several hours in a cold wind without a reduction of body temperature.

Rubner5 has measured the effect of baths and douches lasting three and a half to five minutes. When the water has a temperature of 16° he finds that the carbon dioxid elimina-tion may be very largely increased, specially in the case of the douche. The effect of the douche was more marked if taken before breakfast when the intestinal tract was free from food. The results before breakfast were as follows:

1 Johansson: "Skan. Archiv fur Physiologie," 1897, vii, 123. 2 Sjostrom: "Skan. Archiv fur Physiologie," 1913, xxx, 1. 3 Rubner: "Energiegesetze," 1902, p. 203.

4 Lefevre: "Comptes rendus," 1894, p. 604.

5 Rubner: "Archiv fur Hygiene," 1903, xlvi, 390.

Influence Of Cold Baths On Metabolism In Man

A cold bath, especially a douche, will therefore stimulate to a greatly increased metabolism. The mechanical stimulus of the falling cold water apparently acts reflexly to increase the metabolism greatly, as it certainly does the magnitude of the respiration. The respiratory quotient indicates that the increased metabolism is at the expense of the glycogen supply. There is an after-effect which lasts about one and a half hours, indicating an increased metabolism during that time. This may be the expression of the body's attempt to maintain a normal temperature after being somewhat cooled (see also p. 322).

It is obvious that a cold bath will be likely to induce shivering unless by mechanical effort, such as swimming, the metabo-lism is increased so as to supply calorific energy in another way than through chemical regulation (see p. 312).

A bath of 350 has no effect on metabolism.

Rubner finds that a bath at 44° again increases the metabolism, the increase being, for the volume of respiration, 18.8 per cent., for carbon dioxid 32.1 per cent., and for oxygen 17.3 per cent. This is probably due to the overwarming of the cells. Baths at this temperature find favor among the Japanese.

Lusk1 found that immersion before breakfast of men in baths at a temperature of 8° which contained cracked ice increased the heat production during a subsequent period of violent shivering to 180 per cent, above the normal. The metabolism was the equivalent of 4500 calories per day for a man weighing 64.7 kilograms. From the respiratory quotient of 0.85 which was found, it may be computed that approximately half of this energy was derived from carbohydrates and half from fat. It is known that cold tends to remove glycogen from the animal body (see p. 458), and it has been shown by Freund and Marchand1 that a low environmental temperature increases the amount of sugar in the blood.

1 Lusk: "American Journal of Physiology," 1910-11, xxvii, 427.

Schapals2 brings confirmatory evidence as to the outcome of immersion of men in hot and cold baths:

The higher respiratory quotients obtained may in part be due to a quickened respiration and consequent elimination from the blood of carbon dioxid not belonging to the metabolism of the period. The German term "Auspumpung" properly defines this procedure. In metabolism work this possibility should be always sharply borne in mind.