152 ANSWERS TO PRACTICAL QUESTIONS 



They fill the pores of the skin, and thus prevent the pas- 

 sage of the perspiration. Moreover, they often contain sub- 

 stances which are poisonous, and being carried in by the absorb- 

 ents cause disease. 



8. Is water-proof clothing healthful for constant wear ? 



No. It retains the insensible perspiration by which waste 

 matter is being constantly thrown off from the system. 



9. Why are rubbers cold to the feet ? 



They retain the insensible perspiration. The moisture which 

 gathers absorbs the heat of the feet, and readily conducts it 

 from the body. 



10. Why does the heat seem oppressive ivhen the air is 

 moist ? 



In the moisture-laden atmosphere, the evaporation of the 

 insensible perspiration from the surface of the body goes on 

 slowly. The heat, which would otherwise pass off through the 

 pores, is retained in the system. 



11. Why is friction of the skin invigorating after a 

 cold bath ? 



(See Physiology, p. 64, 65.) 



The friction produces heat, expands the veins, etc., on the 

 surface, and, calling the blood in that direction, produces a 

 vigorous circulation. In other words, it causes a reaction.* 



* Strength in the living body is maintained by the full but natural 

 exercise of each organ ; and, as we have seen, the actions of these por- 

 tions of the nervous system is made dependent upon influences conveyed 

 to them by the sensitive nerves distributed over the various parts of the 

 body. And among these the nerves passing to the skin are the chief. The 

 full access of all healthful stimuli to the surface, and its freedom from all 

 that irritates or impedes its functions, are the first external conditions of 

 the normal vigor of this nervous circle. Among these stimuli, fresh air 

 and pure water hold the first place. Sufficient warmth is second. The 

 great and even wonderful advantages of cleanliness are partly referable to 

 the direct influence of a skin healthily active, open to all the natural 

 stimuli, and free from morbid irritation, upon the nerve-centers of which 

 it is the appointed excitant. This influence is altogether distinct from 

 those cleansing functions which the healthy skin performs for the blood ; 

 and in any just estimate of its value is far too important to be over- 

 looked. HINTOJT. 



