AND THEIR FUNCTIONS. 175 



The medium-sized ducts may be the optic nerves, except 

 that they are said to pass to the cerebelhim. Aristotle says 

 that they come into contact with, or fall on, each other 

 {sy??ipiptousi) , and that this is well seen in fishes, suggesting 

 that he had seen the meeting or crossing of the optic nerves. 

 Aristotle's description is insufficient for the determination of 

 the other ducts. Dissections of various animals, especially 

 fishes, made for the purpose of determining these ducts, have 

 not enabled me to arrive at a conclusion. 



The next passage to be considered is much less ambigu- 

 ous. Aristotle says : " The brain of the chamseleon is a 

 little above its eyes and continuous (ffwsx^i) with them."* 

 This shows as clearly as any passage can be expected to do 

 that he saw the optic nerves of the chamseleon to their full 

 extent, yet, as has been stated already, he did not admit 

 that the brain was in unbroken connection with the sense 

 organs. He did not understand the nature of the nerves 

 which he saw. On the contrary, it seems that he considered 

 them to be ducts conveying nutriment or other fluid, for he 

 says that the purest of the moisture about the brain is 

 separated through the ducts which are seen to lead from 

 the eyes to the membrane about the brain, f 



Not one of the passages relating to the ducts between 

 the brain and sense organs is as clear as that already given 

 about the chamaeleon. It seems strange that, after having 

 exposed the optic nerve by dissection in the way which that 

 passage suggests, he should have adhered to his belief in the 

 want of an unbroken connection between the substance of 

 the brain and any of the sense organs. 



There are a few other passages which are difficult 

 and are consistent only in showing that he did not 

 believe in such a connection. In H. A. i. c. 9, s. 1, it is 

 stated that no duct (to'/joj) extends from the brain to either 

 ear, but a blood-vessel extends from the brain to each ear ; 

 in P. A. ii. c. 10, 6566, however, it is stated that a duct ex- 

 tends from each ear to the back part of the head. The 

 effect of the various passages previously cited is to show 

 that the ducts, whatever their real nature may be, do not 

 lead to the substance of the brain, but to some part of the 

 blood system, and so communicate with the heart, 

 Aristotle's centre of sensation. 



There is an interesting passage which bears upon the 



* H. A. ii. c. 7, s. 5. f G. A. ii. c. 6, 744fl. 



