APPENDAGES OF THE SKIN. fou 
and presents, especially under the anterior part of the body, numerous longitudin- 
ally-arranged papille. The part of the corium under the body i is termed the nail 
Horny part of nail 
—Stratum mucosum 
Nail bed 
— Vallum 
= Terminal 
phalanx 
Fic. 5389.—TRANSVERSE SECTION OF A NAIL. 
bed ; that under the root, the nail matrix. The deep part of the nail consists of 
the stratum germinativum and stratum mucosum, while its superticial horny portion 
is constituted by a greatly thickened stratum lucidum, and consists of nucleated, 
keratinised squames. The stratum corneum is represented by the thin cuticular 
fold overlapping the lunula, and termed the eponychium, while the stratum granu- 
losum can only be traced as far forwards as the nail root. 
_ Root of nail 
Eponychium 
Horny part of 
Stratuin—_22=333355 
mucosum Nail matrix 
1G. 540.—LONGITUDINAL SECTION THROUGH RooT OF NAIL. 
Hairs.—Hairs (pili) are well developed on the scalp, pubes, and margins of the 
eyelids, in the axilla, the vestibule of the nose, and at the entrance to the concha, 
and also on the face of the male. Those on the genitals and face appear about 
puberty. Rudimentary over the greater part of the body, they are entirely absent 
on the flexor surfaces of the hands and feet, over the dorsal aspect of the terminal 
phalanges, the glans penis, the inner surface of the prepuce, and inner aspect of the 
labia. Marked variations, individual and racial, exist as to the colour of the hair, 
and also as to the manner of its growth; hence the terms straight, curly, woolly, 
etc., are used to designate it. Straight hairs are coarser than curly ones, and have, 
moreover, a circular or oval outline on transverse section, curly hairs being flat 
and riband-like. 
The root of the hair (radix pili) is embedded in a depression of the skin, termed 
the hair follicle (Fig. 556); while the free portion is named the stem or shaft, and 
consists from without-inwards of three parts, viz. cuticle, cortex,and medulla. The 
cuticle is formed by a layer of imbricated scales which overlap one another from 
below upwards. The cortex consists of longitudinally-arranged fibres made up of 
elongated, closely-appled, fusiform cells, which contain pigment and sometimes air 
spaces, the latter especially in white hairs. The medulla, absent from the fine 
hairs of the body generally and from the hairs of young children, forms a central 
core, which appears black by transmitted and white by reflected light, and is 
composed of polyhedral nucleated cells containing pigment, fat granules, and air 
spaces. 
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