154 ANSWERS TO PRACTICAL QUESTIONS 



10. Why does the heat seem oppressive when 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. 



1 1. Why is friction of the skin invigorating after a cold 

 bath? 



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

 the surface, and, calling the blood in that direction, pro- 

 duces a vigorous circulation. In other words, it causes a 

 reaction.* 



(See Physiology, page 75.) 



12. Why does the hair of domestic animals become rough- 

 ened in winter ? 



(See Question 2.) 



The effect is beneficial, since more air a non-conduc- 

 tor of heat is retained by the hair, and thus the rough 



* " 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 portions of the ner- 

 vous 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 im- 

 pedes 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 advan- 

 tages of cleanliness are partly referable to the direct influence of a skin 

 healthily active, open to all the natural stimuli, and free from morbid irrita- 

 tion, upon the nerve-centres of which it is the appointed excitant. This influ- 

 ence 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 overlooked." HINTON. 



