424 THE SKIN. 



epidermis. In the tactile hairs of animals, the nerves were described by Schobl 

 as passing upwards over the outer root-sheath, losing their white substance, and 

 forming a close plexus with vertical meshes ; finally ending in an annular expan- 

 sion, which encircles the hair just below the orifices of the sebaceous glands, and is 

 in immediate connection with the hyaline layer of the follicle. This statement has 

 been generally confirmed, except that the annular expansion of Schobl has been 

 shown to be an annular ramification of pale fibres amongst the cells of the outer root- 

 sheath, some of the nerve-fibres becoming more superficial again and terminating in 

 irregular, disk-like enlargements between the root-sheath and the hyaline layer. 

 Ordinary hairs receive fewer nerve-fibres, but, as in the tactile hairs, most of these 

 appear to end in the outer root-sheath at about the level of the orifices of the seba- 

 ceous glands. In the larger tactile hairs the bulb is surrounded by cavernous tissue, 

 which lies between the outer and middle layers of the dermic coat. 



Muscles of the hairs. Slender bundles of plain muscular tissue (arrectores 

 pili) are connected with the hair-follicles (figs. 481, 484). They arise, generally, by 

 a number of fasciculi, from the most superficial part of the coriurn, and joining to 

 form a somewhat flattened and plexiform muscle they pass down obliquely to be 

 inserted into the outside of the follicle below the sebaceous glands, which they in a 



Fig. 484. SECTION OF THE SKIN OF THE HEAD, WITH TWO HAIR-FOLLICLES. DIAGRAMMATIC. 



(Kb)liker.) 



a, epidermis ; 6, corium ; c, muscles of the hair-follicles. 



Fig. 485. HAIR-RUDIMENT FROM AN EMBRYO OF six WEEKS, MAGNIFIED 350 DIAMETERS. (Kblliker.) 



a, horny, and b, mucous or Malpighian layer of cuticle ; !, limitary membrane ; m, cells (some of 

 which are assuming an oblong figure) which chiefly form the future hair. 



measure embrace in their passage. In the dermic coat of the follicle some of the 

 muscular fibres become transverse, and partly encircle the lower part of the follicle. 

 They are placed on the side to which the hair slopes, so that their action in elevating 

 the hair is evident. When the hairs are in groups, as in the scalp, one muscle may 

 divide as it passes to its insertion, and may be attached to several follicles (Hesse). 

 In some parts a muscular slip is sent more deeply into the integument and becomes 

 attached to the connective tissue which encloses a sweat-gland. 



Development of hair in the foetus. The rudiments of the hairs may be dis- 

 cerned at the end of the third or beginning of the fourth month of intra-uterine 

 life, as little black specks beneath the cuticle. They are formed of down-growths of 

 the Malpighian layer, which sink into the corium (fig. 485). A homogeneous limit- 

 ing membrane is seen (z), inclosing the collection of cells, and continuous above 

 with a similar simple film Avhich at this time lies between the cuticle and the 

 corium ; it becomes the innermost or hyaline layer of the dermic coat of the follicle. 

 The hair-rudiment next lengthens and swells out at the bottom, so as to assume a 

 flask-shape, and it is now found fitted over a papilla which has become formed in 

 the subjacent corium. Outside the limitary membrane, the fibres, corpuscles, and 

 other constituents of the dermic coat of the follicle become formed. While this is 



