April 1, 1899.] 



KNOWLEDGE. 



75 



they retain their pigment, and thus cause the hair to be 

 coloured. In this respect these lower cells of the mucos^im 

 di£fer in their behaviour from what we have seen in the 



Fio. 3. — The same as Fig. 2, mui-e hi^lily magnified, a. The 

 deeper cells of the epidermic layers, loaded with pigment ; b, shows 

 where the epidermic layers are everted over the surface of the papilla ; 

 c, the papilla, an upgrowth from the dermic sheath ; d, the dermic 

 sheath . 



integument, for there they remain pigmented only in the 

 deeper layers. As was stated in the previous article, if we 

 adopt the accepted view with regard to the regeneration 

 of the more superficial cells of the epidermis, we have 

 to account for the disappearance of the pigment within 

 these cells of the miu-osum as they advance to the surface, 

 but as was pointed out in the same article, the accepted 

 view appears to us untenable, and necessitates the explana- 

 tion of the disappearance of the pigment in the super- 

 ficial layer of cells, which disappearance curiously does 

 not occur in the hair, although it is probably subjected to 

 similar influences. The view we suggested, viz., that the 

 intermediate layers of the epidermis, i.e., the striUum 

 yranulosum and stratum conicum, were the active layers, 

 and that growth occurred in 

 two directions, i.e., towards 

 the surface and towards the 

 true skin, would at once over- 

 come all difficulties — diffi- 

 culties which are still further 

 emphasized when we come to 

 deal with the coloured races. 

 If the reader has followed 

 the description given above, 

 he will recognize that the 

 evagination of the layers of 

 the sheath over the papilla 

 at the base of the follicle leads 

 to an aversion of these layers, 

 so that the deep layers of the 

 mucomiii, no longer imprison- 

 ed by contact with the super- 

 ficial aspect of thecMfis lerci, 

 are now thrown outwards over the surface of the papilla and 

 pushed onward into the sheath. So long as there is pig- 

 ment to absorb these cells will retain it ; but as the deeper 

 layers of the mucosum, which rest on the surface of ihe cutis 

 vera, cannot be displaced, the pigment remains there per- 



manently ; whereas over the surface of the papilla, the cells, 

 constantly shifting, carry with them the pigment, they have 

 absorbed, into the body of the hair ; when, however, that 

 supply of pigment ceases, there is no longer any for the 

 moving cells to absorb, the consequence being that the 

 cells forming the hair are now colourless, and so the 

 hair appears on the surface as grey at the root. In this 

 way we have a simple explanation why a negro may have 

 grey hair and yet retain the blackness of his skin ; in the 

 former situation the pigment-loaded cells are shed, and 



Fig, 4. — Longitudinal section 

 sebaceous gland and hair muscle, t 

 c. muscle of hair. 



through hair follicle, showing 

 , Hair shaft ; h, sebaceous gland ; 



cease to be coloured when there is no more pigment to be 

 absorbed ; in the latter situation the cells constitute a per- 

 manent layer, which never advances to the surface, and 

 therefore retain for indefinite periods the pigment which 

 has been taken up. 



The question of the manner of production of the 

 straight and curly varieties of the hair has long been 

 a matter of conjecture, and hitherto no satisfactory 

 explanation has been forthcoming. There are a number 



Fia. 



Straight Hair, a. Hair foUicle, 

 with hair shaft inside ; h, 

 hair muscle ; c, sebaceous 

 gland. 



Straight 

 Muscle 

 inside ; 

 gland. 



Hair erected by action of 



a. Hair follicle, with hair 



A, hair muscle ; c, sebaceous 



Curved Hair (Bushman). 

 a, Curved follicle, with 

 hair inside ; i, hair 

 muscle ; c, sebaceous 

 glands. 



of facts which it appears to us are of importance in the 

 consideration of this question. Each hair foUicle is pro- 

 vided with a sebaceous gland opening into it, together with 

 a muscle connected with it ; these are well represented in 

 the photomicrograph (Fig. i). The size of the gland 



