412 TEGUMENTAL SYSTEM. 



friction soon destroys it, for I have never been able myself to 

 obtain any distinct demonstration of such a tunic. Bichat, in- 

 deed, denies its existence altogether. Those who have subjected 

 large quantities of hair to chemical analysis have found its com- 

 position to be very similar to that of horn or cuticle ; but it 

 has been a matter of dispute whether the stem is formed of a 

 single case, or whether it consists of filaments including two or 

 more canals in their interstices : from the observations of those 

 who have most extensively and minutely inquired into this part 

 of comparative anatomy, it would appear that bristles, and 

 what is called horse-hair, are filamentous, but that the finer 

 hairs are simply tubular. From the summit of the pulp pro- 

 ceeds an elongation of soft matter into the cavity of the stem, 

 which, from its outward resemblance to it, by many is regarded 

 as a process or continuation of the pulp itself; but Bichat avers, 

 that it is a distinct substance, and, though he acknowledges his 

 ignorance of the true organization of it, maintains that it is a 

 vital part, and that it is the seat of the colouring principle of the 

 hair. For my own part, whatever may be the nature of this 

 particular substance, I am inclined to agree with the learned 

 writer of the article " Hair," in Rees' Cyclopsedia, " that the 

 colouring matter pervades the horny tube of the hair, to which 

 it communicates an uniform stain or dye, in the same manner as 

 the substance of a horn or hoof is coloured." 



Identity. — All hair has a common similarity in its structure 

 and mode of growth ; whether it assume the nature of human 

 hair, that of the coat or mane of the horse, the wool of the 

 sheep, the fur of the rabbit, the bristles of the hog, or the 

 spines of the hedgehog: its particular varieties in every one of 

 these animals being owing simply to the quality and disposition 

 of the fibres of its cuticular case. The coat varies in quality, 

 colour, and length, in horses of various breeds: the Arabian, the 

 racer of this country, is characterized by his smooth, silken, and 

 glossy coat; the cart-horse, the Shetland pony, and the 

 northern horses in general, are contradistinguished by the 

 greater length and consequent roughness, the coarseness, and 

 stubbornness of their hair. 



Colour. — With regard to colour, I have already had occasion 

 to remark, that there is some connexion between that of the 

 skin, the hair, and the eyes : black horses have black skins and 

 dark eyes; milk-white and cream-coloured horses, light skins 

 and wall eyes. The three primitive colours, those of which all 

 the other appear to be either shades or combinations are white, 

 red, and black. According to Richerand, the lighter the shade 

 the finer the hair; as a proof of which, he says, there are fewest 



