almost invisible to the naked eye. When we are at rest the flow of perspiration, though constant, is seldom so free that it does not evaporate almost as rapidly as it exudes, so that the skin is only kept pleasantly moist; but during exercise, especially in warm weather, the cutaneous surface becomes covered with drops of fluid.
When the pores of the skin are partly choked up, so that they cannot perform their work properly, some of this duty of purifying and regulating the volume of the blood is thrown upon certain internal organs, such as the kidneys or intestines; and should these happen to be weak, diseased, or already overtasked, serious disturbance may be quickly brought on throughout the whole system. Hence the importance of keeping the skin of the whole body clean by the free use of the bath.
Warm Baths.—For purposes of cleanliness, the baths par excellence are those of warm water, this term being applied to those in which water of a temperature from 70° to 80° Fahrenheit is employed.
Liquids of this degree of heat usually give a sensation of warmth when placed in contact with the human skin, and therefore avoid the disadvantages of the shock to our systems produced by a cold bath (that is, below 60°), and the excessive stimulation resulting from a hot bath, i.e., one of 85° and upwards. Soap or alkali in some form is necessary to remove the fatty matter poured out by the oil glands already described, and for most people there is nothing better than the old-fashioned white Castile. Many persons are apt to remain too long in a warm bath, and care should be taken to avoid this error which, if often indulged in, has a very debilitating effect on the system.
The frequency with which a warm bath should be repeated varies with different individuals. A safe rule, to which of course there are exceptions, is to bathe the body twice a week in winter and every other day in summer, gradually increasing the frequency to a tri-weekly washing in winter and a daily one in summer, if experience proves that better health is secured by such a habit.
It is very important to avoid being exposed to cool air after immersion in a warm bath, because the blood vessels of the skin being dilated from the stimulation of the warm water, the amount of prespiration poured out upon the skin, and consequently also the cooling effect of evaporation from the cutaneous surface are greater, and the danger of contracting a chill is much increased.
The condition is accurately expressed by the popular saying that a warm bath "opens the pores," although the exact mechanism by which this opening is accomplished is not so generally understood. The best time for a warm bath for those who are in robust health, but are liable to take cold, is in the evening, when they can go to bed at once, and so avoid all exposure for some hours afterwards. Invalids, however, and those of a delicate constitution, will often find that they endure the exertion of taking a bath best about 11 o'clock in the morn-