242 STUDIES IN PHYSIOLOGY 



should frequently be moistened and pushed back ; otherwise 

 this outer skin is likely to become torn and to form the so- 

 called " hangnails." These are often a source of great dis- 

 comfort and sometimes of danger, for they furnish a possible 

 opening for infection by bacteria. 



Treatment of Burns. We have already suggested the 

 treatment for cuts .and bruises of the skin in connection with 

 the blood system (see p. 153). Another form of accident that 

 may injure the skin is a burn. The affected part should be 

 covered with a paste of baking soda, which tends to lessen 

 the pain by keeping out the air and by reducing the inflamma- 

 tion. A mixture of linseed oil and limewater (known as 

 carron oil) is also a good remedy to keep on hand for burns. 

 If the clothing of a person catches fire, the flames should be 

 extinguished by wrapping him quickly in thick clothing or 

 pieces of carpet. 



Clothing. The warmth of certain kinds of cloth depends 

 upon the fact that they keep the heat of the body from 

 escaping ; in other words, they are poor conductors of heat. 

 Good conductors, on the other hand, allow the heat to pass 

 off rapidly. This difference in fabrics is largely due to the 

 way they are woven. Wool, for instance, is usually made 

 into cloth that is loose in texture, and thus it can hold a 

 considerable amount of air in its meshes. Now, dry air is 

 a poor conductor of heat. Woolen clothing is therefore 

 generally used for winter wear. Cotton and linen are 

 tightly woven, and heat radiation through these materials 

 is rapid. 



The color of clothing, too, is of considerable importance. 

 This can be shown by experimenting with two pieces of ice, 

 both exposed to summer heat. If we cover one piece of 

 ice with a dark shade of cloth, and the other piece with a 

 yellow or white shade of the same material, we shall find 

 that the ice melts more rapidly under the former. This 

 means that dark colors absorb the heat rays of the sun, 

 while the light shades tend to reflect the heat. For this 



