$38 PHILOSOPHY OF ZOOLOGY. 
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passes through the corium, mucous web and cuticle. It 
usually raises up small scales of this last layer, which soon 
become dry and fall off, but do not form the external co- 
vering of the hair, as some have supposed. 
The hair itself consists of an external horny covering, 
and a central vascular part, termed medulla or pith. ‘This 
horny covering consists of numerous filaments placed la- 
terally, to which different kinds of hair owe their striated 
appearance. These filaments appear to be of unequal 
lengths ; those nearest the centre being longest ; and, con- 
sequently, the hair assumes the form of an elongated cone, 
with its base seated in the skin. This form gives to the 
hair that peculiar property, on which the operation of felt- 
ing depends. 
When we take hold ofa hair by the base with the fingers 
of one hand, and draw it between two of the fingers of the 
other, from the root towards the point, it feels smooth to 
the touch; but if we reverse its position, and draw it be- 
tween the fingers from the poimt to the root, we feel its 
surface rough, and it offers a considerable resistance. 
The surface of the hair must, therefore, consist of emi- 
nences pointing to the distal extremity. In consequence of 
this structure of the surface, if a hair is seized at the middle 
between two fingers, and rubbed by them, the root will gra- 
dually recede, while the poimt of the hair will approach 
the fingers ; in other words, the hair will exhibit a progres- 
sive motion in the direction of the root, the imbricated sur- 
face preventing all motion in the opposite direction. 
It is owing to this state of the surface of hairs, that 
woollen cloth, however soft and pliable, excites a disagree- 
able sensation of the skin, in those not accustomed to wear 
it. It likewise irritates sores, by these asperities, and excites 
inflammation. The surface of lmen cloth, on the other hand, 
feels smooth, because the fibres of which it consists, possess 
