240 APPLIED PHYSIOLOGY 



does not feel chilled on entering the cold air. When by 

 exercise the body feels warm, the overcoat may be unbut- 

 toned or removed, but while one is resting it should be put 

 on at once before the body feels chilly. Cold air blowing 

 on our body while it is heated may cause us to have pains 



in our muscles and joints. 



> 



423. Airing clothes at night. At night it is usually best to 

 remove all clothing worn during the day. Woolens have the power of 

 absorbing a great deal of moisture without feeling damp. But the 

 moisture and the waste matters from the skin should be removed each 

 night by thoroughly airing the underclothes. If it is not done, the 

 woolen may become so saturated with moisture that it affords no more 

 protection than cotton, and so may render a person liable to take cold. 



424. Beds. Feather beds and thick quilts enable a 

 person to get warm when he goes to bed on a cold night, 

 but after he falls asleep he becomes too warm and per- 

 spires too freely. Then he throws off the coverings, and 

 soon the evaporation of the perspiration makes him cold. 

 We should use as thin bed covers as possible so as to avoid 

 overheating. If we sleep in a very cold room, we can keep 

 ourselves comfortably warm with light covers if we use 

 woolen blankets for sheets instead of sheets made of linen 

 or cotton. As a rule a plain mattress is more comfortable 

 and gives a more even heat than a feather bed; but in 

 beds, as in clothing, a person's sensation forms the best 

 guide as to the kind to be used. 



425. Effect of lowering the temperature of the body. 

 In extremely cold weather heat may be lost from the body 

 faster than it can be produced, and thus the temperature 

 falls. Then the body and mind cannot act, but become 

 numb and sluggish, just as the hands become numb and 

 powerless when cold. If the temperature continues to fall, 

 the respiration becomes less, and as the cells cease to act 



