APPEND* 



1067 



the finger it is connected with the under surface of the nail a little behind its free 

 edge. The cuticle and the horny substance of the nail (both epidermic structures) 

 are thus directly continuous with each other. The superficial, horny part of the 

 nail consists of a greatly thickened stratum lucidum, the stratum corneum forming 

 merely the thin cuticular fold (eponychium) which overlaps the lunula; the deeper 

 part consists of the stratum mucosum. The cells in contact with the papilla? of the 

 matrix are columnar in form and arranged perpendicularly to the surface; those 

 which succeed them are of a rounded or polygonal form, the more superficial ones 

 becoming broad, thin, and flattened, and so closely packed as to make the limits 

 of the cells very indistinct. The nails grow in length by the proliferation of the 

 cells of the stratum mucosum at the root of the nail, and in thickness from that 

 part of the stratum mucosum which underlies the lunula. 



Eponychium _ 



Nail _ 

 Stratum 

 mucosum : 



Stratum cor- 

 neum of the r 

 nail groove ~. 



&- Blood-vessel 



FIG. 943. Longitudinal section through nail and its nail groove (sulcus). 



pan 



Hairs (pill) are found on nearly every part of the surface of the body, but are 

 absent from the palms of the hands, the soles of the feet, the dorsal surfaces of the 

 terminal phalanges, the glans penis, the inner surface of the prepuce, and the 

 inner surfaces of the labia. They vary much in length, thickness, and color in 

 different parts of the body and in different races of mankind. In some parts, as 

 in the skin of the eyelids, they are so short as not to project beyond the follicles 

 containing them; in others, as upon the scalp, they are of considerable length; 

 again, in other parts, as the eyelashes, the hairs of the pubic region, and the whiskers 

 and beard, they are remarkable for their thickness. Straight hairs are stronger 

 than curly hairs, and present on transverse section a cylindrical or oval outline; 

 curly hairs, on the other hand, are flattened. A hair consists of a root, the part im- 

 planted in the skin ; and a shaft or scapus, the portion projecting from the surface. 



The root of the hair (radix pili) ends in an enlargement, the hair bulb, which is 

 whiter in color and softer in texture than the shaft, and is lodged in a follicular 

 involution of the epidermis called the hair follicle (Fig. 944). When the hair is of 

 considerable length the follicle extends into the subcutaneous cellular tissue. The 

 hair follicle commences on the surface of the skin with a funnel-shaped opening, 

 and passes inward in an oblique or curved direction the latter in curly hairs to 

 become dilated at its deep extremity, where it corresponds with the hair bulb. 

 Opening into the follicle, near its free extremity, are the ducts of one or more 

 sebaceous glands. At the bottom of each hair follicle is a small conical, vascular 

 eminence or papilla, similar in every respect to those found upon the surface of the 

 skin; it is continuous with the dermic layer of the follicle, and is supplied with 

 nerve fibrils. The hair follicle consists of two coats an outer or dermic, and an 

 inner or epidermic. 



The outer or dermic coat is formed mainly of fibrous tissue; it is continuous 

 with the corium, is highly vascular, and supplied by numerous minute nervous 

 filaments. It consists of three layers (Fig. 945). The most internal is a hyaline 

 basement membrane, which is well-marked in the larger hair follicles, but is not 



