OF ANIMALS. 29 



similar in any respect to that of the most perfect animals with which 

 we are in general more acquainted. It consists of a pulpy substance, 

 somewhat transparent, which is easily squeezed out when the brain is 

 cut into. It appears in some, and perhaps in all the lower classes 

 that have brains, in the shape of a ring, from the circumference of 

 which arise the nerves, as radii from a centre. Through this ring (in 

 such) passes the oesophagus. I am apt to believe, however, that this 

 ring is not wholly brain, but a union of two large lateral nerves, which 

 unite under the oesophagus. This at least appears to be the case with 

 the next class. It is not enclosed in hard parts, and is not defended 

 from pressure or injuries more than any other internal part. 



This class woidd appear to have but two senses, viz. feeling and 

 taste, having neither seeing nor hearing, and most probably without 

 the sense of smell. There appears to be no organ for such a sensation, 

 and the respiratory organ is so situated as not to be of any service to 

 taste, to which smelling is certainly a director. 



Of the Second Class, or Insects. — The class of animals immediately 

 superior in sensation to the foregoing is (I believe) that class called 

 'Insects,' both aerial and aquatic. "We find in them an increase of 

 senses. The first class we were inclinable to believe had but two senses ; 

 but here we are pretty certain of four, viz. touch, taste, hearing*, and 

 sight : how far they have smell I have not been able to discover, but 

 should doubt itf. 



The brain lies in the head of the animal, and consists of a small 

 rounded body, giving off nerves in all directions to the different parts 

 about the head, such as the optic nerve, &c. The brain is a pulpy 

 substance, somewhat transparent, which gives it a bluish cast. From 

 the posterior or lower part of the brain, close to one another, go out 

 two large nerves ; one passes on each side of the oesophagus, and they 

 then unite into one, forming a knot at this union J. They disunite 

 again, and so unite and disunite alternately through the whole length 

 of the animal, at every union giving off the nerves, as from the brain. 

 This structure I suspect answers both the use of a medulla spinalis and 

 the great intercostal nerve 1 . 



* It is pretty certain that bees hear. 



t Yet it would appear from observation that it is very probable that bees and 

 wasps have smell. 



\ It is the union of these two nerves, and the oesophagus passing through between 

 them, which made me suppose that that in the Snail was a similar structure. 



luscous subkingdom of Cuvier, whence it may be inferred that Hunter had a percep- 

 tion of that great natural subdivision of the animal kingdom]. 



1 [The complicated abdominal cord of Insects has since been accurately figured 

 and described by Lyonet and other anatomists, and has recently been successfully 



