CH. XL.] 



THE SKIN 



605 



and in the palms and soles, where 

 disposed in rows, their presence 

 is indicated by the well-known 

 ridges on the surface. 



The papillse contain loops of 

 capillaries, and in some cases, 

 especially in the palm of the 

 hand and fingers, they contain 

 tactile corpuscles (which will be 

 more fully described in connec- 

 tion with the sense of touch). 

 Special capillary networks are 

 distributed to the sweat-glands, 

 sebaceous glands, and hair fol- 

 licles. 



The deeper portions of the 

 dermis in the scrotum, penis, 

 and nipple, contain involuntary 

 muscular tissue; there is also a 

 bundle of muscular tissue at- 

 tached to each hair follicle. 



The Nails are thickenings of 

 the stratum lucidum. Each lies 

 in a depression called the led of 

 the nail, the posterior part of 

 which is overlapped by epidermis, 

 and called the nail-groove. The 

 dermis beneath is beset with 

 longitudinal ridges instead of 

 papillse ; these are very vascular ; 

 but in the lunula, the crescent at 

 the base of the nail, there are 

 papillse, and this part is not so 

 vascular. 



The Hairs are epidermal 

 growths, contained in pits called 

 hair follicles. The part within 

 the follicle is called the root of 

 the hair. 



The main substance of the 

 hair is composed of pigmented 

 horny fibrous material, in reality 

 long fibrillated cells. It is covered 

 by a layer of scales imbricated 

 upwards (hair cuticle). In many 



the papillae are largest and are 



< 



^ v 



FIG. 388. Vertical section through the skin of tho 

 sole of the foot, a, Horny layer ; b, stratum 

 granulosum; c, stratum lucidum; d, Mal- 

 pighian layer ; e, cutis vera ; /, papilla of 

 cutis vera ; g, fat lobule of subcutaneous 

 tissue; h, sweat-gland; i, orifice of sweat- 

 duct. (Szymonowicz.) 



