GENERATION OF ANIMALS, V. n.-iii. 



cised at a distance is possessed by man to a lesser 

 degree, in proportion to his size, than almost any 

 other animal ; on the other hand, he is better than 

 any of them at accurately perceiving the differences 

 in the objects perceived. The reason is that in man 

 the sense-organ is pure and least earthy and cor- 

 poreal, and besides that, nature has given him, for 

 his size, the thinnest skin that any animal has. 



Nature has brought off a clever piece of work in the 

 seal, too, which, although it is a viviparous quad- 

 ruped, possesses no ears but passages merely. The 

 reason is that it spends its life in a fluid medium. 

 The ear is a part of the body which is an addition 

 made to the passages in order to safeguard the move- 

 ment of the air" which comes from a distance, and 

 therefore it is no use to the seal ; indeed it would 

 actually be a hindrance rather than a help, because 

 it would act as a receptacle for a large volume of 

 water. 



This concludes our remarks about sight, hearing 

 and smell. 



The various kinds of growths of hair. — In human III 

 beings these differ in the same individuals at different ^'an«t'«s 

 periods of life, and they differ also in comparison 

 with the other animals that have hair. Practically 

 all the animals which are internally \iviparous have 

 hair ; I say " all," because the spines which some 

 of them have on the body must be considered as 

 being a kind of hair, e.g., the spines of the hedge- 

 hog ** and any other such viviparous creature. Hair 

 exhibits the following differences : it may be hard or 

 soft, long or short, straight or curly, plentiful or 



* Gk. " land-echinus," to distinguish it from the 

 ecfiinus " or sea-urchin. 



511 



