GENERATION OF ANIMALS, V. i.-ii. 



distinct in a pure, clean sight" and they give rise to 

 sense-perception. As for (6) the ability to see things 

 at a distance, and the fact that the movement coming 

 from objects at a distance succeeds in reaching into 

 the eyes, the cause of this is the position of the eyes. 

 Animals with prominent eyes do not see well from 

 a distance, but those with sunken eyes placed in a 

 hollowed recess are able to see things at a distance, 

 because the movement does not get scattered into 

 space but follows a straight course. It makes no 

 difference to this which of the two theories of sight 

 we adopt. Thus, if we say, as some people do, 

 that seeing is effected " by the sight issuing forth,"* 

 then on this theory, unless there is something pro- 

 jecting in front of the eyes, the " sight " of necessity 

 gets scattered and so less of it strikes the object, 

 with the result that distant objects are less well seen. 

 If we say that seeing is effected " by a movement 

 derived from the visible object," then on this theory, 

 the clarity with which the sight sees will of necessity 

 vary directly as the clarity of the movement : dis- 

 tant objects would be 'seen best of all if there were a 

 sort of continuous tube extending straight from the 

 sight to that which is seen, for then the movement 

 which proceeds from the visible objects would not 

 get dissipated ; failing that, the further the tube 

 extends, the greater is bound to be the accuracv 

 with which distant objects are seen. 



These, then, shall be the causes which we assign to 

 explain the different sorts of eyes. 



The same situation is found in connexion with II 

 two other senses — hearing and smell — as with siffht. Keenness of 



rr- 1 1 11 << 1 >> / P Smell and 



lo hear and to smell accurately means (a) to Hearing, 

 perceive as well as possible all the differences in the 



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