736 PHYSIOLOGY. 



stratum mucosum, corresponds to that layer of the epiderm. The 

 nails grow in length by new cells at the root, in thickness by addi- 

 tions beneath the nail. 



The nails serve to protect the skin at the tips of the phalanges, 

 and, at the same time, perfect the touch of the fleshy parts of the 

 fingers. The average growth of the nails is about one-eighth of an 

 inch per month. 





