APPENDAGES OF THE SKIN. 133 



their fluids, which, it is said, lubricate the hair throughout 

 its whole course. (See Fig. 19.) 



The formative force is very great in hair. It is quickly 

 replaced when cut or destroyed, provided the bulb and 

 papilla remain uninjured. Hair is entirely destitute of 

 vitality, except at its root or bulb, where it is both 

 vascular and sensitive, as seen in the disease called plica- 

 polonica. 



The motions of the hair are referred to the action of sub- 

 cutaneous muscles. This is very evident in the large hairs 

 or prickles of the porcupine, and the feathers of the tail of 

 the peafowl, where each is supplied with a distinct muscle 

 for its elevation. 



Hair, like the cuticle, resists putrefaction for a long 

 -time. Boiling resolves it into gelatin and coagulated 

 albumen. According to Vauquelin, hair is composed of 

 an animal matter which forms the base a small quantity 

 of a white concrete oil, a blackish oil, iron, oxide of manga- 

 nese, carbonate of lime, silex, and sulphur. 



The Nails are the horny scales which cover the last 

 phalanx of the fingers and toes. Each nail consists of a 

 root, body, and free extremity. The root and borders are 

 confined in a fold of the cutis, named the nail-follicle; the 

 body rests upon the surface of the cutis, called the matrix, 

 which is very vascular, and appears red; while the white 

 portion, just at the root, is styled the lunula. The nail 

 grows in a manner similar to the cuticle. 



The nail follicle and matrix contain papillae, that 

 secrete the fluid or lymph in which are found cell-germs. 

 These, like those of the hair, become compressed, dry, flat- 

 tened and hardened into nail : those at the root elongating 

 and adding to the length; those at the borders forming 

 the breadth; while those in the matrix, or centre, increase 

 the thickness. 



The nails protect and form a firm support to the tactile 

 papillae or organs of touch. They are also instruments of 

 prehension. 



