46 ii. 10 — ii. 13. 



IS placed in the tongue, the fact is more apparent than in 

 the case of touch, but still not so manifest as in the case of 

 the other senses. However even in taste the fact is evident 

 enough ; for in some animals the tongue is plainly forked.^' 

 The double character of the sensations is however much more 

 conspicuous in the other organs of sense. For there are two 

 ears and two eyes, and the nostrils, though combined together, 

 are also two. Were these latter otherwise disposed and separated 

 from each other as are the ears, neither they nor the nose in 

 which they are placed would be able to perform their office. 

 For in such animals as have nostrils olfaction is effected by 

 means of inspiration,^* and the organ of inspiration is placed in 

 front and in the middle line. This is the reason why nature has 

 brought the two nostrils together and placed them as the central 

 of the three sense-organs, setting them symmetrically on either 

 side of a perpendicular line, where they benefit by the inspiratory 

 motion.^^ In other animals than man the arrangement of these 

 sense-organs is also such as is adapted in each case to the 

 special requirements. (Ch. \\.) For instance in quadrupeds the 

 ears project from the head and are set to all appearance above 

 the eyes. Not that they are in reality above the eyes ; but they 

 seem to be so, because the animal does not stand upright, but 

 has its head hung downwards. This being the usual attitude 

 of the animal when in motion, it is of advantage that its ears 

 shall be high up and very moveable.^ For they can then be 

 turned in all directions, and readily take in sounds from all 

 quarters. (Ch. 12.) In birds, on the other hand, there are no 

 ears, but only the auditory passages.^ This is because their skin 

 is hard and because they have feathers instead of hairs, so that 

 they have not got the proper material for the formation of ears.^ 

 Exactly the same is the case with such oviparous quadrupeds as 

 are clad with scaly plates, and the same explanation applies to 

 them. There is also one of the viviparous quadrupeds, namely 

 the seal, that has no ears but only the auditory passages.^ The 

 explanation of this is that the seal though a quadruped is a 

 quadruped of stunted formation.* 



(C/t. 13.^ Men, and Birds, and Quadrupeds, viviparous and 



oviparous alike, have their eyes protected by lids. In the vivipara 



there are two of these ; and both are used by these animals not 



only in closing the eye, but also in the act of blinking ; whereas 



667 a. 



