TISSUES OF THE BODY. 395 



C . . 50-65 per cent 



H . . . 6-36 



N . . . 17-14 



. 20-85 

 S 5-00 



The amount of sulphur, 4-5 per cent., seems considerable. 



But little is known at present of the nature of that diffused colouring 

 matter which saturates the cortical tissue of the hair, or of the granular 

 pigment of the structure. Those fatty matters which may be extracted 

 in varying amount from hairs appear to contain the ordinary neutral 

 combinations found in other parts of the system. They probably have 

 their origin, for the most part, in the sebaceous glands. 



The ashes of hair amount to from 0*54 to 1*85 per cent. They consist 

 of salts soluble in water, together with phosphate and sulphate of calcium, 

 silicates and oxide of iron (0'058-0'390 per cent.) Manganese, although 

 formerly stated by Vauquelin to exist in the hairs, has not been found 

 by chemists of a later period. That the presence of iron has anything to 

 say to the tint of the latter is very improbable. 



217. 



Hairs are to be found on almost every part of the human body. They 

 are missed, however, on the upper eyelid, the lips, the palm of the hand 

 and sole of the foot, the last joints of the fingers and toes, the inner 

 surface of the prepuce, and on the glans penis. Their size, further, is 

 liable to considerable variation, as we may see from the range in their 

 diameter from 0'15 mm. and upwards down to even 0'0153 mm. A distinc- 

 tion is always made between the very pliant downy hairs (lanugo) and 

 those which are stronger, sometimes pliant and sometimes stiff. No 

 sharp distinction, however, can be drawn between them. The thickest 

 are those of the beard and pubis. The length of the free portion also 

 varies extremely, ranging from 1-2'" among the smaller downy hairs, to 

 45', as on the heads of women. Many hairs, notwithstanding their 

 thickness, remain exceedingly short ; this is the case in the eyebrows 

 (supercilia), eyelashes (cilia), and bristles at the entrance to the anterior 

 nares (vibrissce). The straightness or curliness of hairs depends upon 

 the form of their shaft. In the first instance, the transverse section of 

 the latter is round ; in the second, oval, or even reniform. 



Hairs are found either singly, in pairs, or small groups. The oblique 

 direction of the follicles also brings with it great variety of position in 

 the various localities (Eschricht). In the several parts ol the body the 

 number of hairs likewise is found to vary considerably, so that, while 

 on the scalp 293 have been counted to the square inch, the same super- 

 ficial extent of the chin has only shown 39, and on the anterior aspect of 

 the leg, 13 (Withof). It is hardly necessary to remark that, together 

 with this variation, many individual differences present themselves. 



The structures we are engaged in considering are remarkable for their 

 great strength and elasticity. They will support a considerable weight 

 without breaking, and return almost to their original length again on 

 removal of the extending force, if the latter have not been altogether too 

 great. Owing to their dry and horny composition, they belong to the 

 most durable of all the tissues of the body ; witness the hairs of mummies. 

 They absorb moisture greedily from without in the first place, aqueous 



