58 



THE INTEGUMENT, OR SKIN 



smooth, but covered here and there with minute elevations', 

 called papillce. These are arranged in rows, or ridges, such as 

 those which mark the palm and thumb ; their number is about 

 80 to the square line (a line being one-twelfth of an inch). 

 These papillce contain blood-vessels and nerves also, and are 

 largely concerned in the sense of touch; hence they are 

 abundant where the touch is most delicate, as at the ends 

 of the fingers. The skin is fastened to the underlying tissues 

 by a loose elastic (areolar) tissue. This contains fat during 

 youth and middle life. The gradual absorption of this fat as 



old age approaches gives the 

 skin a wrinkled appearance. 

 This layer is called the sub- 

 cutaneous layer. 



5. The Nails and Hair. 



These are modified forms of 

 the cuticle. 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 ascertained 

 by filing a slight groove on its 



THK ROOT OF A HAIR HIGHLY MAGNIFIED gur f ace? an( J noticing how the 



FIG. 18 



rr.7>. 



of the nail increases, in the 

 course of a few weeks. When the nail is removed by an 

 accident, it will be replaced by a new one, if the root be 

 not injured. (Notes 2 and 6.) 



*The practice of biting the nails should be avoided not only because 

 of the ugly shape which is produced, but because it impairs the sense of 

 touch in the ends of the fingers. In paring the nails, let them remain long 

 enough nearly to cover the pulp of the finger. Avoid scraping either sur- 

 face of the nail ; do not injure the " quick." 



2. The Life of the Cells of the Body. " The life of the body is long 



5. What are the nails and hair ? The growth of the nail ? The rapidity of its growth ? 

 Accident to the nail ? 



