INTERNAL ANATOMY OF INSECTS. 19 



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 

 evenj^/, 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 Geophilus 

 electricus be cut in two, the halves will live and appeal- 

 vigorous even for a fortnight afterwards ; and what is 

 more remarkable, that the tail part always survives the 



a In Lesser Insccto-theol. ii. 84. note *. 

 c 2 



