The skin and the sweat-glands work together to keep the blood at an even temperature, either by giving off heat or in preventing this process in case the outside air is too cool.

The body temperature, as a rule, is higher than that of the outside air, so that heat is generally being given off by the skin.

We are perspiring constantly, but usually to such a slight extent that the fact is hardly noticeable.

The amount of heat which is thrown off at any time is proportional to the amount of the tissue burned up by muscular action..