Q Proceedings of the Royal Physical Society. 



follicles. My own opinion is that we must turn to the 

 consideration of the functions or purposes served by hair 

 in order to obtain a sufficiently satisfactory reason for its 

 shape under different conditions. Being a poor conductor 

 of heat, it will serve as a protection both against cold and 

 extreme heat. In most animals, it also serves as a more 

 or less satisfactory coat for shedding off rain ; and further, 

 it takes an important place as an adornment in connection 

 with sexual selection. 



It seems to me that the shape of the hair should be associ- 

 ated with its function of shedding off water from the body. 

 In the general disposition of hair over the body of an animal, 

 we find that it has a trend which, taken in conjunction with 

 the normal attitude of the animal, admirably adapts it for 

 this purpose. Moreover, in such an animal as the seal, the 

 hairs are so flat that they really become miniature slates, 

 which offer no resistance to the progress of the animal 

 through the water, while they are thoroughly adapted for 

 throwing off water. Further, the hair of one of the lowest 

 of the aboriginal races, viz., the Australian, is decidedly a 

 flattened oval, while among civilised races it is cylindrical. 

 Although I am not able to adduce much direct evidence in 

 support of the statement, yet I am of opinion that the shape 

 of the hair should be primarily associated with climatic 

 conditions, and, as regards animals, also with their rate of 

 progress through the air or water. 



The distribution of hair upon the body is also of extreme 

 interest, and may be correlated with such functions as the 

 maintenance of warmth, and its protective influence against 

 great sun-heat. For these reasons we may attribute its 

 presence upon the scalp to its influence in protecting the 

 brain from direct exposure to the light and heat of the 

 sun. 



The general reduction and apparent disappearance of hair 

 from the body of man, may very well be due either to the 

 wearing of clothing, or else to the absence of the need for 

 such clothing ; for although hair seems to have so entirely 

 disappeared from man's body, yet it is only in a few places 

 that it has been entirely lost, e.g., palms and soles, upper 



