107 



they are 'used almost wholly for purposes of warmth ; but it is evident, 

 that the idea of beauty and distinction is also adraissable from the 

 difference in the fur of various creatures, and in the male and female of 

 the same species. 



In man they are chiefly developed on those parts most exposed to at- 

 mospheric influences, and when the parts beneath are not covered by 

 muscle. The hairs of the perineum and axilla, have the effect of pre- 

 venting the frequent soreness which would be produced by constant 

 motion, between parts softened by constant perspiration. If the surfaces 

 were not mechanically separated by a substance as soft and moveable as 

 the hair, few would escape excoriation or soft warts after a days' long 

 walk. As it is, the perineal hairs are frequently too short to prevent this 

 effect in the rates. 



In the lower animals of the insect and crustacean character, the uses 

 of hair are numerous. It promotes warmth ; it acts as a guard to 

 prevent the ingress of dust &c. into the tracheoe, and is stationed with 

 that especial object at the external orifice, as the hairs are in our own 

 nostrils ; it acts as an additional cuticular expansion for the aeration of 

 the blood ; it is used as an instrument of progression on the tarsi of flies, 

 (fee, on the swimming legs of the entomostraca, and on the tail of the 

 shrimp and lobster. 



Respecting the commercial uses of hair or fur, it is quite unnecessary 

 to enlarge. 



The hair is in fested by its peculiar parasites. We have spoken of one 

 in the bulb — another lives on the hair outside the skin. The pedi- 

 culus pubis, as it is called, is an ordinary louse in all respects except 

 its feet. These are developed so as to enable the creature to embrace 

 the hair, to which it attaches itself with a tremendous grip. The 

 first pair of feet are not so large as the second or third, and are seldom 

 used — two feet only are used at a time. The head is sometimes fur- 

 nished with recurved hooks, by which the animal can fasten itself to 

 the sides of the hair follicle. The egg is fastened to the hair by a 

 transparent cement, and is large enough to be visible to the naked eye. 

 This animal does not confine itself to the pelvis, but has been found on 

 the thighs and legs, the abdomen, chest, axilla, whiskers, eye-brows — as 

 yet I believe it has not been found on the scalp. It is readily destroyed 

 by mercurial ointment, which seems to act as a poison upon it. 



The hair is also attacked by a vegetable parasite, producing the 

 diseases called scalled-head and ring- worm. In the latter case, there is 

 some doubt whether the vegetable is the cause of the disease. I will 

 only remark that I have known the patient apparently to get perfectly 



