204 BIOLOGY AND HUMAN LIFE 



ing this dark pigment. Upon exposure to extreme sunshine we 

 are apt to be burned by the rays, which cause serious injury 

 to the exposed protoplasm. Yet the sunshine is of value in 

 keeping up the health of the skin by promoting brisker circula- 

 tion and active perspiration. It probably also produces in the 

 skin chemical changes of a helpful kind. Moreover, the sun- 

 shine destroys many kinds of bacteria, or germs, and sun baths 

 have been found of great value in the treatment of tuberculosis 

 and rickets. One of the advantages of the ordinary summer 

 vacation, with its swimming and other sports, is the increased 

 exposure of the skin to sunshine. It is wise to expose the skin 

 gradually and get as much tan as possible without getting 

 sunburned. 



170. The hands. The skin of the hands is always exposed to 

 contact with dirt of various kinds, and with bacteria. We should 

 therefore try to keep the hands as clean as possible, especially 

 when we handle food ; and we should keep them away from the 

 mouth or eyes, which are particularly liable to suffer from an 

 introduction of dirt or bacteria. 



The chief value of our hands lies in what we can do with them 

 as wonderful tools ; but as we cannot keep them out of sight, 

 their appearance is a matter of some concern to us. It is worth 

 while to keep the nails well trimmed, to press the cuticle back, 

 to cut off hangnails ; it is worth while to disinfect cuts and 

 scratches, and to keep the fingers out of the mouth, as well as 

 other objects that do not belong there ; it is important to avoid 

 biting the nails ; but it is hardly worth while to treat the hands 

 as though they were ornaments to be exhibited. 



171. The feet. While our feet are generally well concealed 

 from the eyes of other folks, they need in some ways even more 

 care than the hands. A very large proportion of us suffer from 

 cramped toes and misshapen feet resulting from tight or poorly 

 shaped shoes. Most of us suffer because our shoes do not per- 

 mit the water of the perspiration to evaporate from the skin. 

 Many people suffer from corns, which are thickenings of the 

 epidermis resulting from constant pressure, and from bunions, 



