Excretion. 137 



possible. It is dangerous to sit down in wet clothing, even 

 on a warm day. Children seldom take cold from wading, 

 even in cold water, if barefooted ; but with wet shoes and 

 stockings they are likely to take cold. 



Mechanical Protection by the Skin. This is the most 

 evident function of the skin. The skin is tough, strong, 

 and elastic, hence well fitted to cover the body and yield 

 with every motion, yet protect the softer and more delicate 

 tissues beneath it from injury. 



Absorption by the Skin. The skin has slight power of 

 absorption ; hence there is some danger in handling cer- 

 tain poisonous substances. The chief danger, however, is 

 when there are cracks or sores on the hands. If one must 

 handle suspicious material, it is well to rub the hands with 

 vaseline. To use rubber gloves is safer still. 



Review of the Functions of the Skin. (The skin as a 

 sense organ will be considered later.) i. Sensory. 2. 

 Heat-regulating. 3. Absorptive. 4. Protective. 5. Ex- 

 cretory. It will be easy to remember these five functions 

 if it is noted that their initials spell the word s-h-a-p-e. 



Skin-grafting. Sometimes after extensive burns, or 

 other injury of the skin, bits of skin are taken from an- 

 other part of the body, or from another person, and trans- 

 planted to the injured part, where they grow. 



External Features of the Kidneys. The kidneys are a 

 pair of bean-shaped bodies attached to the dorsal wall of 

 the abdomen. (See Fig. 32.) The spot corresponding to 

 the stem-scar of the bean is called the hilum. At this point 

 are three tubes, the artery by which blood enters the kid- 

 ney, the vein by which the blood leaves, and the ureter, by 

 which the urine is conveyed to the bladder, 



