262 APPLIED PHYSIOLOGY 



the perspiration passes off with greater ease, and the skin 

 is made tender. 



471. Hot baths. The heat of a bath in which the body 

 is kept warm from the time it enters the water until it is 

 dry dilates the blood tubes of the skin, so that the blood 

 accumulates upon the surface. Thus the internal organs 

 contain less than their natural supply of blood, and the 

 body is apt to feel weak and drowsy. After mental labor 

 a hot bath may cause the blood to leave the brain and so 

 bring about sleep. When a cold is coming on, a, hot 

 bath may increase the excretion of poisons from the 

 skin. Then the body may be able to overcome the germs 

 of the sickness, and thus the cold may be prevented. 

 The proper time for a hot bath is at night, just before 

 retiring, so that the circulation may become natural before 

 morning. A hot bath requires the use of a warm room, 

 and of a tub sufficiently large to admit most of the body 

 at once, for evaporation of the warm water causes a cold 

 feeling on coming out of the bath. 



472. Cold baths. When a cold bath is taken, the blood 

 tubes of the skin at first contract and give a cold feeling ; 

 but they soon dilate. With the dilatation there comes an in- 

 creased flow of blood throughout the whole body, so that 

 there is a feeling of warmth and vigor in marked contrast 

 with the drowsiness of the hot bath. The invigorating 

 effects of a bath are called its reaction. If a cold bath 

 is long continued, there comes on a second contraction of 

 the arteries, so that the blood is forced within the body, 

 producing a feeling of coldness and weakness from which 

 the body is a long time in recovering. This second con- 

 traction of the blood vessels is called the secondary reaction. 

 The bath should be stopped at the first appearance of a 

 chill. 



