NAILS HAIRS. 65 



NAILS. 



The nails are modifications of the epidermis. Their appearance 

 is too familiar to every one to demand description. That portion 

 which is concealed is called the root^ that which is free or projecting 

 the edge, that attached to the surface of the cutis is the body. The 

 tnalrix is that portion of the cutis under the root and body, which 

 produces the nail. The lunula is that crescentic, white portion of 

 the matrix near the root, and is 

 owing to a want of vascularity. The 

 nail firmly adheres to the matrix, 

 and is moulded upon it like the epi- 

 dermis in other situations. The epi- 

 dermis or cuticle is continuous with 

 the nail, and neither passes over or 

 under it ; being essentially of the 

 same structure. By maceration the 

 epidermis and nail°° can readily be 

 removed from the cutis veraJ^"^ The 

 border of the root of the nail is jagged, 

 thin, and soft, and consists of newly- 

 formed substance ; the deep surface of 



the body is also soft, and marked by longitudinal grooves corre- 

 sponding to the papillary ridgus on the surface of the matrix ; but 

 the edge and superficial portion of the nail is composed of scales 

 more dense and fibrous. 



HAIRS. 



Hairs are found on all parts of the surface, except the palms of 

 the hands, and soles of the feet ; and vary in length, thickness, 

 shape, and colour, according to situation, age, sex, or race. The 

 shaft is that portion projecting beyond the surface ; the bulb is that 

 extremity contained in a follicle of the skin. The cuticular lining 

 of this follicle is continuous with the bulb itself, there being a gradual 

 change in the scales, as they pass from the follicle into the hair; the 

 hair itself grows from the bottom of the follicle, like the nail from 

 the matrix, or the epidermis from the cutis. If the hair is to be 

 coloured, pigment grains are here also developed. 



The human hair is a rod, and not as commonly supposed, a tube. 

 The scales in the axis of the hair are softer, and not so closely con- 

 densed as those of the surface, and thus they contain a larger 

 amount of pigment in the interstices, which produces that dark ap- 

 pearance which is mistaken for a tube ; this loose, porous structure 

 in the middle, is sometimes called the medulla, and the condensed, 

 fibrous exterior is termed the cortex ; the scales of which are im- 

 bricated, that is, overlap each other like the shingles of a roof, 



6* 



