356 THE ANIMALS AND MAN 



effect as it evaporates. The feeling of cold is due to the 

 heat used up by its rapid evaporation. Or, moisten the 

 back of the hand and then blow upon the moistened surface. 

 Then blow upon the dry surface of the other hand. In 

 the latter case, the hand feels the warm breath. In the 

 former case the hand feels cool because the heat is used up 

 in evaporating the water. Thus, when perspiration forms, 

 it evaporates through the use of a large amount of heat. 

 This heat is furnished by the blood and thus the blood is 

 cooled. This is the natural means of cooling the body in 

 a warm atmosphere. 



Importance of cleanliness. — Since the skin is an ex- 

 creting organ of some importance and a heat regulator of 

 much importance the tiny pores of the sweat glands must 

 be kept open and the skin must be kept clean. When 

 perspiration collects upon the surface of the skin, the liquid 

 part quickly evaporates or is absorbed by the underwear. 



The solid substances remain upon the surface of the 

 skin. The cast-off epidermal cells collect there, as well as 

 the many foreign substances with which the skin may come 

 in contact. Even the dust in the air adheres to the oily 

 secretion of the sebaceous glands. Any of these substances 

 would soon clog the tiny pores of the sweat glands and of 

 the sebaceous glands were they not removed by frequent 

 bathing. Vigorous exercise before bathing adds to the 

 benefits of the bath by opening up the pores and covering 

 the skin with its natural secretions. 



Treatment of burn. — In the case of burns or scalds the 

 outer epidermal skin, the natural protector of the dermis, 

 is separated from it and broken, so that the dermis becomes 

 exposed to the air. This is exceeding painful. A burn 

 should therefore be covered at once with a paste of baking 

 soda or thick oil. This will keep out the air and reduce 

 the inflammation. A mixture of lime water and linseed 

 oil is also a good remedy for scalds. 



