APPENDAGES OF THE SKIN. 



859 



from view and embedded in a fold of skin ; the body, or uncovered part, rests 

 on the corium and ends in, a free margin. The greater part of the lateral margin 

 is overlapped by a duplicature of skin, termed the vallum unguis or nail-wall. 

 The nails are pink in colour, with the exception of a small semilunar area 

 near the root, which is more opaque than the rest, and is named the lunula. The 

 lunulse diminish in size from the thumb towards the little finger, while the 

 thickness of the nail diminishes towards its root and lateral margins. The corium 

 under the nail is highly vascular and sensitive, and presents, especially under 



- Horny part of nail 



Stratum mucosum 

 Nail bed 



Vallum 





FIG. 736. TRANSVERSE SECTION OF A NAIL. 



anterior part of the body, numerous longitudinally arranged ridges. The part 

 of the corium under the body is termed the 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 superficial 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 granulosum can be traced only as 

 far forwards as the nail root. 



Root of nail 



Nail matrix 



FIG. 737. LONGITUDINAL SECTION THROUGH ROOT OF NAIL. 



Pili. Hairs are well developed on the external genitals, scalp, 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. Eudimentary over the greater part of the body, they are entirely absent 

 from the flexor surfaces of the hands and feet, the dorsal surfaces of the terminal 

 phalanges, the glans penis, the inner surface of the prepuce, and medial surfaces 

 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 is embedded in a depression of the skin, termed the hair 

 follicle (Fig. 738); the free portion is named the scapus or shaft, and consists 



