THE INTEGUMENT, OR SKIN. 



43 



skin, and although very unlike the cuticle as it appears on 

 the surface of the body, they are, in reality, modified forms 

 of that layer of the skin. The nail grows from a fold of 

 the cuticle at the root, and from the under surface. As 

 fast as it is formed, it is 

 constantly being pushed 

 outward. The rapidity of 

 its growth can be ascer- 

 tained by filing a slight 

 groove on its surface, and 

 noticing how the space be- 

 tween it and the root of 

 the nail increases, in the 

 course of a few weeks. 

 When the nail is removed 

 by any accident, it will be 

 replaced by a new one, if 

 the root be not injured. 



6. The hairs are pro- 

 duced in a similar manner ; 



5. The hair sac. 

 c. TRANSVERSE SECTION OF A HAIR. 



Fig. 14. 



o, b. THE ROOT op A HAIR. 

 the Skm forming depreS- i, 2 , 3 . The skin forming the hair sac. 4. 



sions, or hair sacs, from 

 the bottom of which they 

 grow and are nourished (Fig. 14). They are found, of 

 greater or less length, on almost all parts of the surface, 

 except the palms of the hands and soles of the feet. On 

 certain parts of the body, they grow to great length ; on 

 other parts they are so short, that they do not rise beyond 

 the hair sac in which they originate. 



7. The bulb, or root, from which the hair arises, is 

 lodged in a small pouch, or depression in the skin. The 

 shaft is the part which grows out beyond the level of the 

 skin. Its growth is altogether in one direction, in length 

 alone. The outer part of the hair is quite firm, while its 



6. How are the hairs produced ? Difference in their length ? 



7. Root of the hair ? Shaft ? Firmness and softness ofthe hair? 



