xii THE SKIN AND THE KIDNEYS 153 



pits, called hair follicles, in which the roots of the hairs 

 are embedded. They secrete a natural oil for the hair 

 and skin. This keeps the skin in a soft and pliable 

 condition and protects the body against absorbing too 

 much moisture from the air. These glands are espe- 

 cially numerous on the face but occur all over the body 

 except on the soles and palms. 



116. Appendages of the Skin. On the end of each 

 finger and toe the true skin is covered by a piece of 

 very much modified horny epidermis called a nail. The 

 sides and root of the nail are covered by folds of the 

 skin in such a way as to 

 make a little pocket, out 

 of which the nail appears 

 to grow. The nails, like 

 the epidermis, are without 

 nerves and blood vessels. 



The nail itself is COlorleSS FIG. 78. A vertical section of a finger 



and quite transparent. naii (Zuppke). 



The pink color is due to numerous capillaries in the nail 

 bed beneath. Nails grow by the formation of new cells at 

 their roots, which slowly push the nail forward. If the 

 epidermis overhanging the root and the sides of the 

 nail is not carefully pushed back every few days, it may 

 become broken and tear up into the flesh, forming the 

 so-called hangnails. The hangnails should not be pulled 

 out but cut off close to the skin. Besides being very 

 painful, they offer little openings through which poison- 

 ous matter may enter the blood. The nails should be 

 washed with soap and warm water and carefully cleaned 



