INTERNAL ANATOMY OF INSECTS. ll) 
After duly considering this general outline of the ner- 
vous system of insects, the question will continually oc- 
cur to you, — is then what you have called the brain the 
sensorium commune of these animals, in the same manner 
as it is in those with warm blood ? To this query a ne- 
gative must be returned. In the latter, the brain is the 
common centre to which, by means of the nerves and 
spinal marrow, all the sensations of the animal are con- 
veyed, and in which all its perceptions terminate. The 
nerves and spinal marrow are merely the roads by which 
the sensations travel ; and if their communication with 
the brain, by any means be cut off at the neck, the whole 
trunk of the animal becomes paralytic, evidently proving 
that the organ by which it feels is the brain. This, how- 
ever, is so far from being the case in insects, that in them, 
if the head be cut off, the remainder of the body will 
continue to give proofs of life and sensation longer than 
the head : both portions will live after the separation, 
sometimes for a considerable period ; but the largest will 
survive the longest, and will move, walk, and occasionally 
evenjh/, at first almost as actively without the head, as 
when united to it. Lyonet informs us, that he has seen 
motion in the body of a wasp three days after it had been 
separated from the head; and that a caterpillar even 
walked some days after that operation; and when touched, 
the headless animal made the same movements as when 
intire a . Dr. Shaw has observed — an observation con- 
firmed in Unzer's Kleine Schriften, — that if Geophilns 
electricus be cut in two, the halves will live and appear 
vigorous even for a fortnight afterwards ; and what is 
more remarkable, that the tail part always survives the 
* In Lesser Insecto-theol. ii. 84. note *. 
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