HAIR. 



[ 310 ] 



HAIR. 



The hairs sometimes found developed upon 

 mucous membranes, and within encysted 

 tumours and ovarian cysts, possess the nor- 

 mal structure in every respect. 



Of the morbid states of the human hair, 

 we need mention only the loss and change 

 of colour, and the presence of fungi. When 

 the colour entirely vanishes, and the hair 

 becomes white or grey, the cells of the me- 

 dulla contain abundance of air. This arises 

 from a kind of degeneration or impaired nu- 

 trition ; the liquid contents of the cells are 

 not supplied in sufficient quantity; they 

 therefore evaporate, and the cells being pre- 

 vented from collapsing by their adhesion to 

 each other and to the firm cortex, become 

 filled with air, which replaces what would 

 otherwise constitute a vacuum. Fungi are 

 found in FAVUS upon the cortex of the hair, 

 within the follicles, and even within the hair 

 itself, as is stated. In Porrigo decalvans also, 

 fungi are stated to occur in the hairs ; we 

 can affirm positively that this is not correct, 

 even when the disease has lasted for years. 



The principal differences between the hair 

 of man and of animals, and that of animals 

 from each other, relate to 1, the size; 2, 

 the relative proportions of the cortical and 

 medullary structures ; 3, the locality of the 

 pigment ; 4, the arrangement of the medul- 

 lary cells; 5, the comparative amount of 

 true hair, and woolly hair, down, or wool; 

 and 6, the size and projection of the super- 

 ficial cortical cells or scales, upon which the 

 valuable property of felting depends. Of 

 these we shall give a brief sketch (PL 1. 

 figs. 1-3, and PL 22). 



The hair of the Mammalia generally is 

 formed upon the same plan as that of man ; 

 great variety, however, exists in its com- 

 plexity of structure and the arrangement of 

 the component parts. 



Quadrumana (PI. 22. figs. 4 & 5). In the 

 monkey (Indian) (fig. 4), the hair presents 

 much of the same structure as in man ; the 

 pigment is confined to the cortex, but the air- 

 cells of the medulla are larger and less 

 crowded ; this is seen to a greater extent in 

 the hair of the lemur (fig. 5). 



Cheiroptera. In the bats (PL 1. fig. 2; 

 PL 22. figs. 6 & 7), a striking character is 

 the peculiar development of the cortical 

 scales of the surface. In the hair of the 

 common bat (PL 1. fig. 2), which is one of 

 the TEST-OBJECTS, and Australian bat (PL 

 22. fig. 7), this character is not so striking 

 as in that of the Indian bat (PL 22. fig. 6), 

 in which the scales are grouped in whorls at 



pretty regular intervals along the shaft, and 

 project considerably beyond the surface. 

 The pigment is principally confined to these 

 whorled scales. In some of the white hairs 

 of the bat, the individual scales are very 

 beautifully seen (PL 1. fig. 2 c). 



Insectivora. The hair of the mole (fig. 8) 

 bears some resemblance to that of the bats ; 

 but the cells of the medulla are very distinct. 

 (See SPINES). 



Carnivora (figs. 9-13). In this Class the 

 structure of the hair varies considerably. In 

 the lion (fig. 9) the cortical cells are distinct, 

 but not projecting ; the medullary cells 

 are very numerous, and the air-spaces mi- 

 nute, but closely aggregated, as we often 

 find them in the human hair. In the bear 

 (fig. 10), the large hairs present much the 

 same structure as in the lion ; the wool-hairs 

 differ strikingly from these, however, in the 

 distinctness of the cortical and medullary 

 cells. 



Pachydermata (figs. 14-17). In this Class 

 the hairs present a development correspond- 

 ing with that of the skin ; being very thick 

 and complex in structure. In the elephant 

 (fig. 15, transverse section), each hair resem- 

 bles a number of hairs fused together. 

 Scattered through its substance are pale spots 

 formed by cells containing little or no pig- 

 ment, with an irregular perforation in each, 

 probably arising from rupture of the cells. 

 Surrounding these medullary centres are 

 innumerable cortical cells loaded with pig- 

 ment. In the pig (fig. 16), the distinction 

 between the cortex and medulla is not well 

 marked, and the cells assume a radial direc- 

 tion, as indicated by those which contain 

 most pigment. In the Cheiropotamus (fig. 

 17) the distinction is more evident. 



Ruminantia (figs. 18-22). In this Class 

 the hair presents great variety. In the camel 

 (fig. 18) and dromedary (fig. 19), the true 

 hair exhibits much the same structure as 

 that of the higher classes ; whilst in the 

 deer (fig. 20, moose-deer; fig. 21, musk- 

 deer) the medullary portion is enormously 

 developed at the expense of the cortical 

 portion ; in no hairs is the cellular structure 

 more distinct than in the two latter, the 

 medulla closely resembling a piece of vege- 

 table cellular tissue. The wool-hair in this 

 class presents the characteristic structure. 

 That of the camel (fig. 18 b) agrees in struc- 

 ture with the type of wool from the sheep 

 (fig. 22) in its softness, flexibility and wavi- 

 ness, and in the distinctness of the cortical 

 cells. 



