11. 14. 49 



hairless, have none. The Libyan ostrich, indeed, forms an excep- 

 tion ; for, though a bird, it is furnished with eyelashes.^ This 

 exception, however, will be explained hereafter. Of hairy animals, 

 man alone has lashes on both lids. For in quadrupeds there is 

 a greater abundance of hair on the back than on the under side of 

 the body ; whereas in man the contrary is the case, and the hair 

 is more abundant on the front surface than on the back. The 

 reason for this is that hair is intended to serve as a protection 

 to its possessor. Now, in quadrupeds, owing to their inclined 

 attitude, the under or anterior surface does not require so much 

 protection as the back, and is therefore left bald, in spite of its 

 being the nobler of the two sides. But in man, owing to his 

 upright attitude, the anterior and posterior surfaces of the body 

 are on an equality as regards need of protection. Nature there- 

 fore has assigned the protective covering to the nobler of the two 

 surfaces ;2 for invariably she brings about the best arrangement 

 of such as are possible. This then is the reason that there is no 

 lower eyelash in any quadruped ; though in some a few scattered 

 hairs sprout out under the lower lid,^ This also is the reason 

 that they never have hair in the axillae, nor on the pubes, as man 

 has. Their hair, then, instead of being collected in these parts, 

 is either thickly set over the whole dorsal surface, as is the case 

 for instance in dogs, or, sometimes, forms a mane, as in horses 

 and the like, or as in the male lion, where the mane is still more 

 flowing and ample. So, again, whenever there is a tail of any 

 length, nature decks it with hair, with long hair if the stem of the 

 tail be short, as in horses, with short hair if the stem be long, 

 regard also being had to the condition of the rest of the body.* 

 For nature invariably distributes her material, by subtracting 

 from one part and giving to another. Thus when she has covered 

 the general surface of an animal's body with an excess of hair, 

 she leaves a deficiency in the region of the back. This for instance 

 is the case with bears.'^ 



No animal has so much hair on the head as man. This in 

 the first place is the necessary result of the fluid character of 

 his brain, and of the presence of so many sutures in his skull. 

 For wherever there is the most fluid and the most heat, 

 there also must necessarily occur the greatest outgrowth.^ 

 But, secondly, the thickness of the hair in this part has a final 

 cause, being intended to protect the head, by preserving it from 

 658b. 4 



