ADDITIONAL TOPICS IN HUMAN BIOLOGY 141 



pores on every square inch of the surface of the palm, and that the 

 total number of these glands in one's skin is about 2,500,000. 



202. Importance of bathing. — The oil glands and perspiratory 

 glands are constantly pouring their secretions in greater or less quan- 

 tity upon the skin. As the water evaporates, the oil and the solid 

 ingredients of the sweat are left behind. Unless these are removed, 

 they tend to clog the openings of the ducts from the glands and so to 

 interfere with the work of the skin. A considerable amount of these 

 substances is doubtless worn away, together with the scales of the 

 outer skin, by friction against the clothing. But if the skin is to 

 carry on its functions to the best advantage, and if decency is to be 

 maintained, frequent baths must be taken. 



203. Kinds of baths. — The oily secretions and much of the 

 accumulated dirt on exposed surfaces of the skin can be removed only 

 by the use of warm water and soap ; hence these should be employed 

 upon the hands two or three times a day and at least once or twice a 

 week upon the whole body. Warm baths should be employed, how- 

 ever, for their cleansing effect only, since they are usually followed 

 by a feeling of lassitude. One is much more likely to catch cold, too, 

 after exposure to warm water, as it opens the pores of the skin, causes 

 the arteries near the surface to dilate, and thus increases the amount 

 of perspiration. Unless the warm bath is taken just before going 

 to bed, it should be followed by a quick appUcation of cold water. 



Cold baths, on the other hand, if taken under proper conditions, 

 have an exhilarating effect. The body should then be rubbed vigor- 

 ously with a coarse towel. If after a cold bath one does not feel a 

 warm glow, the bath is injurious rather than beneficial. 



Baths should never be taken immediately after eating, since the 

 blood is thereby drawn away from the organs of digestion. Nor 

 should one remain in cold water until one feels a chiU. Shower 

 baths, however, are better than a cold plunge, for they stimulate 

 both by the cool temperature of the water and by the force with 

 which it strikes the skin. 



204. Care of the hair. — The oil glands are most numerous in 

 the scalp, and if the skin is in a healthy condition, the hair is supplied 



