44 ii- 10. 



furnished with flesh ; and they account for the absence of this 

 substance by saying that it is intended to add to the perfection 

 of sensation. For the brain they assert to be the organ of 

 sensation ; and sensation, they say, cannot penetrate to parts 

 that are too thickly covered with flesh. But neither part of this 

 statement is true. On the contrary, were the region of the 

 brain thickly covered with flesh, the very purpose for which 

 animals are provided with a brain would be directly contravened. 

 For the brain would itself be heated to excess and so quite 

 unable to cool any other part ; and, as to the latter half of 

 their statement, the brain cannot be the cause of any of the 

 sensations, seeing that it is itself as utterly without feeling as 

 any one of the excretions. These writers see that certain of the 

 senses are located in the head, and are unable to discern any 

 reason for this ; they see also that the brain is the most peculiar 

 of all the animal organs ; and out of these facts they form an 

 argument, by which they link sensation and brain together.^ It 

 has however already been clearly set forth in the treatise on 

 Sensation, that it is the region of the heart that constitutes the 

 sensory centre. There also it was stated that two of the 

 senses, namely touch and taste, are manifestly directly dependent 

 on the heart ; ^" and that as regards the other three, namely 

 hearing, sight, and the centrally placed sense of smell, it is the 

 character of their sense-organs '^ which causes them to be 

 lodged as a rule in the head. Vision is so placed in all animals.^^ 

 But such is not invariably the case with hearing or with smell. 

 For fishes and the like hear and smell, and yet have no visible 

 organs for these senses in the head ; ^^ a fact which demonstrates 

 the accuracy of the opinion here maintained. Now that vision, 

 whenever it exists, should be in the neighbourhood of the brain is 

 but what one would rationally expect. For the brain is fluid ^* 

 and cold, and vision is of the character of water,'^ water being of 

 all transparent substances the one most easily confined.'^ More- 

 over it cannot but necessarily be that the more precise senses 

 will have their precision rendered still greater if ministered to 

 by parts that have the purest ^^ blood. For the motion of the 

 heat of blood destroys sensory activity. For these reasons 

 the organs of the precise senses are lodged in the head. 



It is not only the fore part of the head that is destitute of 

 flesh, but the hind part also. For, in all animals that have a 

 fi66b. 



