GENERATION OF ANIMALS, V. m. 



tributory cause is the difference of the fluid present 

 in it : in some this is greasy, in others watery. In 

 general, of course, the fundamental nature of the 

 skin is earthy in substance : being on the surface of 

 the body it becomes solid and earthy as the fluid 

 evaporates off. Now the hair and its counterparts 

 are formed not out of the flesh but out of the skin [as 

 the fluid in them evaporates and exhales ; thus thick 

 hair is formed out of thick skin and thin hair out of 

 thin skin].*' If, then, the skin tends to be looseknit 

 and thick, the hair is thick both on account of the 

 large amount of earthy matter and on account of the 

 size of the passages ; but if the skin tends to be 

 compact, the hair is thin on account of the narrowness 

 of the passages. Further, if the moisture is watery, 

 it quickly dries off and the hair does not attain to any 

 size, though it does if the moisture is greasy, because 

 greasy matter does not readily dry off. Thus, gener- 

 ally speaking, thick-skinned animals have thick hair*; 

 but it is not true that the thickest-skinned have 

 thicker hair than (the others in the same categorj^), 

 for the causes mentioned, an example being afforded 

 by the pig tribe when compared A\-ith that of oxen, 

 or \\ith the elephant and many other animals. For 

 the same cause, too, our hair is thickest on the head : 

 the skin there is thickest and situated over the largest 

 amount of fluid,*^ and besides that it is verv loosely 

 knit. And the reason why the hair is long [or short] 

 is that the fluid which evaporates is not easily dried 

 off. There are two causes which prevent it being 

 easily dried off : one is its quantity, the other its 



" These words are deleted by Piatt as partly unintelligible 

 and as not fitting in with what follows. 



" But see 783 a. 2. ' Viz., the brain. 



515 



