14. 



KNOWLEDGE. 



[April 1. 1899. 



view of man's descent, what more immediately concerns 

 us are the variations met with in the texture and appear 

 anoe of his head hair, for advantage is taken of these 

 differences to help to classify the various races of man. 

 We have already referred to the importance of hair as an 

 index of colour, and we took occasion in a previous article 

 to point out that, under ordinary conditions, there was a 

 limit to its use in this respect, for what appeared to us as 

 black hair might contain a much less amount of pigment 

 than another sample, which appeared no blacker, if one 

 may use such an expression. We then stated that the 

 only satisfactory way of estimating the "blackness " of the 

 hair was to extract the pigment from samples of equal 

 weight. 



But apart altogether from the question of pigment, we 

 have the texture of the hair to consider. We are all 

 familiar with what we term coarse and fine hair. Coarseness 

 here implies that the individual hair is thick as compared 

 with the fine variety. This thickness imparts to the hair 

 a wiriness, which causes it in bulk to be less amenable to 

 the use of the brush and comb than the thin or sleek 

 variety. Furthermore, a thick hair may contain pro- 

 portionately less pigment than a fine hair, weight for 

 weight ; the pigment is, as it were, present in more dilute 

 form, so that the colour is not so pronounced, an explanation 

 why the hair of the beard and moustache usually appears 

 lighter in tint than the finer head hair. Again, some 

 hair is straight, some wavy, and some curly. We find, 

 as a rule, that thick hair is the straightest, whilst 

 the finest hair is that which constitutes the "woolly" 

 hair of the negro and negrito. Wavy hair is usually a 

 hair of intermediate thickness. But hitherto we have 

 assumed that all hair is of the same shape, that is, cylin- 

 drical on section. This we shall find presently is not the case. 

 It is now many years since Pruner Bey drew attention to this 

 difiference in the hair of man. By making sections of 

 different head hairs, he demonstrated that every variety 

 between that displaying a circular form on section and that 

 showing an oval or flattened section was met with. The 



-H a 



Fig. 1 — Section through scalp of a Bushman, showing curved 

 hair follicles cut transTersely (a), and longitudinally (b). In the 

 centre of the hair follicle a, the flattened form of the section of the 

 hair is eeen. 



circular section is characteristic of straight hair, either 

 fine or coarse ; the flattened form of curly or " woolly " 

 hair ; whilst the wavy variety displays intermediate 



forms. At that time this difference in the form of the 

 hair was considered a sufficient explanation of its straight- 

 ness, curliness or waviness, and it was not till some years 

 later that Prof. Charles Stewart, of the Koyal College of 

 Surgeons Museum, pointed out that not only was the hair 

 of the negro curly, but the follicle within which it grew 

 was also curved (Fig. 1). This naturally leads us to a 

 consideration of the structure of a hair follicle. 



In a previous article, some account was given of 

 the structure of the skin, which consists of the dermis, 

 or true skin, and the epidermis, scarf skin, or cuticle, 

 which overlies it ; the latter is further sub-divided 

 into two strata, a superficial horny layer, and a deeper 

 juicy layer, the rete mucosum : between these there is an 

 intermediate folium, comprising the stratum ijranulosum 

 and stratum lucidum. If the reader can conceive these 

 superficial layers as pushed downwards around some solid 

 cylinder into the substance of the true skin, or even 

 onward, into the subjacent tissue, he will be able to form 

 some idea of the manner in which the sheath of the hair 

 is formed. The bottom of the recess so produced has 

 projected into it from the vascular dermis or true skin a 

 papilla like growth. Around this the layers of the in- 



FiG. 2. — Photomicrograpli of section through hair follicle. The 

 root of the hair is displaced so as to show more distinctly the dermic 

 covering and papilla, and the epidermic sheathes, a, Hair shaft; 

 h, epidermic lining of sheath ; c, dermic sheath of follicle ; d marks the 

 point where the eversion of the epidermic layers takes place over the 

 surface of the papilla ; e, papilla of the dermic sheath ;_/", subcutaneous 

 tissue. 



vaginated sheath are reflected, and as at this point, o.wing 

 to its greater vascularity, the cell growth is most active, it 

 follows that the cells of the mucosum which are proliferating 

 most freely are thrown on to the surface of the papilla, and 

 having no room to accumulate within the sheath, are 

 gradually pushed along it so as to appear ultimately at its 

 orifice on the surface of the body. Now, the evagination 

 of the layers at the bottom of the sheath, dependent on the 

 presence of the papilla, naturally leads to the eversion 

 of the horny layer as well, so that we have a hair 

 formed, the outer cells of which are homy, whilst the 

 inner are soft, and form the core or meduUa. The softer 

 cells of the mucosum, as they advance over the surface of 

 the papilla, naturally absorb the pigment which is brought 

 to them by the blood and lymph streams, but as they advance 



* KNOWLEoaE, February, p. 25. 



