384 THE POPULAR SCIENCE MONTHLY. 



fortunately for the parasite theory, it is among "the classes" who 

 are certainly above suspicion so far as parasites are concerned 

 that the loss of hair on the head is most conspicuously shown, 

 while in the case of Hodge, who can not be regarded in the same 

 manner, loss of hair from the head is decidedly rare. An explana- 

 tion which pretends to account for what has taken place, and yet 

 fails in apjDlication to analogous circumstances at the present day, 

 is not one to be accepted. A true explanation of the loss of hair 

 will explain the present-day loss as well as that of the past ; 

 the loss of hair from the head as well as that from the body ; 

 the loss of hair by the elephant as compared with the mammoth ; 

 the loss of hair on the chests of old monkeys ; the loss of hair 

 during disease in animals generally ; the loss of hair during preg- 

 nancy in domestic and other animals; the loss of feathers by 

 penned-up fowls. An explanation which is wholly physiological, 

 and accounts for loss of hair as a pathematic symptom of indi- 

 vidual or racial decline, assumes that such loss of hair is an exem- 

 plification of a law of reversion, that as progressive ontogenetic 

 or phylogenetic development is, necessarily, progressive acquire- 

 ment or elaboration, retrogressive development in similar cases is, 

 accordingly, loss or degeneration of character developed during 

 progression. This explanation, together with the assumption 

 warranted by evidence, that the longer any character or particu- 

 lar feature has been transmitted in the race, the longer it will 

 withstand adverse influences, may be applied to all the instances 

 of hair-loss given above. 



In connection with the hair it may be noticed that certain 

 peculiarities in its mode of growth had their origin in the habits 

 of monkeylike ancestors. On a child's head the hair grows from 

 the crown to the forehead ; but in animals which move head-first 

 on all fours a rabbit, for instance it may be noticed that the 

 hair is always directed from front to back, a character acquired 

 by the fact of motion through air in a given direction having 

 imparted a given lie to the hair. Such may be assumed to 

 have been the case with the hair in the ancestors of monkeys ; 

 but when it is found, as in Cehus vellerosus, that the hair 

 grows the contrary way namely, from back to front some 

 cause must have induced the change. The flow of rain may 

 be cited the head being hung down, so that the crown is the 

 highest part, and the rain flows off in all directions, giving 

 the hair a lie in accordance. Now, flow of rain in the case of 

 quadrupeds, as well as the tendency of hair to grow according to 

 gravity, unless other causes are more potent, has made the hair 

 on their limbs grow from the body to the extremities. In the 

 case of man, however, and certain monkeys, the hair on the fore- 

 arm grows in just the contrary direction namely, toward the 



