GENERATION OF ANIMALS, V. iii. 



quality. Thus, if there is a great deal of the fluid, 

 and also if it is greasy, it does not easily dry off. 

 And that is why the hair on our heads is the longest : 

 the brain, being fluid and cold, pro\"ides fluid in large 

 abundance. 



Straight hair and curly hair" is due to the exhala- 

 tion in it : if this exhalation is smoky,* being hot 

 and dry it makes the hair curly ; for the hair gets 

 bent because it is subjected to the impulse of two 

 directional motions — the earthy constituent urges 

 its way downwards, the hot constituent upwards ; 

 and as the hair will easily bend on account of its 

 weakness, it gets t\\-isted ; that is what curliness of 

 the hair reallv is. Well, that is one cause that mav 

 be assigned for it : here is another. It may equally 

 well be that, owing to its containing but little fluid 

 as against a great deal of earthy matter, the hair gets 

 dried by its environment and so contracts. Any- 

 thing that is straight bends if its vapour is drawn off, 

 and shrinks up like a hair burning on the fire, which 

 would imply that the curliness of hair is a contraction 

 due to lack of fluid caused by the heat of its environ- 

 ment. In favour of this is the fact that curlv hair is 

 also harder than straight hair, and of course anything 

 dry is hard. Animals that contain a great deal of 

 fluid have straight hair, because in their hair the 

 fluid advances in a continuous stream and not drop 

 by drop. That is why the Scythians by the Black 

 Sea and the Thracians have straight hair : both their 

 constitution and the environing air are fluid (moist). 



halation '" : the " smoky," a compound of Air and Earth, 

 which is hot and dry; and the " aqueous," which is cold 

 and moist. For further details see De sensu 443 a 21 ff., 

 Metei/r. 360 a 22 ff., cf. G.A. 784 b 10. 



^ 517 



