24« 



SCIENCE-GOSSIP. 



Fig. 3. — Hairs of a few familiar animals x 300. — [J.R.L.] a, large hair 

 of a mouse ; b, from the back of a mouse: c, from the hog's back : d, from 

 the back of a badger ; c, f, from the back of a rabbit ; g, from the back 

 of a cat ; /;, wool from sheep. 



the sebaceous glands, and projecting obliquely from 

 the latter are the hairs. 



The hair and its appendages consist merely of 

 these elements somewhat displaced and modified. 

 The epidermis becomes pitted in, and from the 

 bottom of the 

 pits or hair 

 follicles there 

 grow the hairs. 

 The stratum cor- 

 neum is only 

 continued about 

 a quarter of the 

 distance down 

 the follicle. The 

 stratum Malpigh ii 

 is continued 

 down the follicle 

 as the outer root 

 sheath ; at the 

 bottom of the 

 follicle it covers 

 a vacular pa- 

 pilla, and from 

 this and its covering the hair is formed. The 

 stratum granulosum and stratum lucidium form Henle's 

 and Huxley's layers of the inner root sheath and 

 are reflected over the hair, the former as the cuticle 

 of the hair, the latter as the cuticle of the follicle. 

 External to the outer root sheath is a thin hyaline 

 layer, a kind of basement membrane ; and a strong 

 fibrous covering, the inner fibres of which are 

 arranged circularly. The latter have been 

 erroneously thought to be non-striped muscle 

 cells. Dr. Wilson has noticed in the nose ten 

 hairs projecting from one com- 

 mon follicle. 



The hair itself is enclosed in 

 a layer of squames called the 

 cuticle. They are imbricated so 

 that the margins of the cells 

 point upwards. The cuticle of 

 the follicle is also composed of 

 imbricated squames, the free 

 edges of which look down- 

 ward. This is an important 

 arrangement, for it is princi- 

 pally by it that the hair is 

 held in position, the two lay- 

 ers interlocking in a dovetail 

 fashion. When the hair is 

 pulled out of the skin it 

 carries with it the layers 

 forming the follicle, thus the}- have been called the 

 root-sheaths. The hair consists of a cortex and a 

 pith or medulla. In the hairs of some animals 

 the medulla is absent, such as woolly hairs. 

 Occasionally one sees a human hair with more than 

 one medulla. The cortex consists of horny spindle- 



k I m 



Fig. 4. — k, human head hair ; /. human 

 beard hair; m. hair from the back of 

 orang-outang. — "After Cunningham.] 



shaped cells arranged longitudinally. The medulla 

 consists of rectangular cells in one or several rows, 

 arranged differently in different animals, and air 

 spaces. By their arrangement the hair of different 

 animals, as will afterwards be shown, can be dis- 

 tinguished. This 

 recognition is 

 occasionally 

 some impor- 

 tance in medico- 

 legal cases. At 

 about the posi- 

 tion where the 

 stratum corneum 

 stops in its con- 

 tinuation down 

 the follicle the 

 secretion of 

 certain glands 

 is emptied. This 

 secretion, called 

 " sebum/' which 

 protects the 

 hair and follicle, 

 is not a secretion in the ordinary sense of the word ; 

 certain cells, free in the lumina of the gland, bodily 

 degenerate, and thus form sebum. 



This sebum is all that is necessary for the 

 good keeping of the hair, and if people w~ould wash 

 their hair occasionally in tepid water only, no 

 outside preparation such as oil or pomade would 

 be necessary. When nature perceives that outside 

 material is being applied to the hair, she promptly 

 stops her supply of sebum. Attached to the true skin 

 and to the bottom of the follicle, stretching across 

 the obtuse angle formed by the 

 hair and the skin, is a muscle, 

 which, by its contraction, 

 erects the hair. This muscle 

 is known as the arrector pili 

 muscle. It is supplied by 

 the pilo-motor nerve, w-hich 

 is probably in connection with 

 a pilo-motor centre in the 

 brain. By contraction, the 

 arrector pili muscles cause 

 "goose skin." The gland 

 opening into the hair follicle 

 is placed in the triangle 

 formed by the skin, hair and 

 arrector pili; thus contraction 

 of this muscle cannot take 

 place without the gland 

 being compressed and its secretion forced out. The 

 pilo-motor nerves have been traced in the monkey 

 and the cat. The pigment, which gives to the hair 

 its colour, is placed partly in the fibres and partly 

 between the fibres of the cortex. 



The following is a scheme of the layers entering 



