It must be remembered that anything which creates a greater activity of the tissues, such as muscular exercise, liberates a greater amount of heat. The reverse is also true;—a decrease in the amount of muscular movement means a decrease of heat liberated. During exercise, a large amount of fat, protein, and dextrose (sugar) are released by the movements and oxidized; the liberated heat is carried to all parts of the system and the temperature is raised. Mental work, for the same reason, tends to raise the body temperature, though to a much less degree. Food in the alimentary canal causes an activity in the glands of the digestive organs and also increases the temperature. Of course, while digestion and mental and muscular activity are at their height, the body temperature is highest. These activities usually reach a maximum in the afternoon and the temperature is then highest, while, as a rule, it decreases from about six at night until four or five in the morning, when it is usually at its lowest ebb. This is a point of importance to physicians. Even five degrees above the average human temperature, if recorded about six at night, is not considered abnormal. Anything which causes an increase in heat radiation, as perspiration, lowers the temperature, and the open pores of the skin are valuable aids in equalizing the body heat. A person who perspires freely does not suffer with heat, during excessive exercise, as does one whose pores are closed. One ready means of regulating the body heat is the _bath_. If one takes a hot bath, the temperature is materially raised by the artificial heat, but there is a recompense in the increase of heat radiation from the skin. If one takes a cold bath, the immediate effect is cooling, but the activity set up within, to create a reaction, soon heats the body to a greater degree than before the bath. The best way to increase the evaporation and thus decrease the temperature of the body is with a tepid shower or a tepid sponge. The tepid water is not so extreme as to create a strong reaction and it will cause a marked decrease in temperature. Thus, for fever patients or for a warm day, the tepid shower or sponge is commended; for a cold day, or for the individual whose circulation is sluggish, the cold bath is desirable. Where the vitality is low, so that there is not sufficient reaction, the bath must be tempered. Heat generation is also increased by solid foods that require more than normal activity on the part of the glands for digestion. For this reason the food for fever patients should be that most easily digested and should be reduced to the minimum to keep up the strength. Diuretic foods and beverages, which increase the activity of the skin and the kidneys, also tend to lower the body temperature.