INTERNAL ANATOMY OF INSECTS. 21 
the above resemblance to the brain of vertebrates into 
consideration, there appears ground for thinking that 
the nervous system of insects, like some of their arti- 
culations’, is of a mixed kind, combining in it both the ce- 
rebro-spinal and the ganglionic systems; and this will 
appear further if we consider its functions. 
That learned and acute physiologist Dr. Virey, assum- 
ing as an hypothesis, that the structure of the system in 
question is simply ganglionic, and merely analogous to 
the sympathetic system of vertebrate animals, has built 
a theory upon the assumption, which appears evidently 
contradicted by facts. Because, as he conceives after 
Cuvier, insects are not gifted with a real brain and spinal 
marrow, he would make it a necessary consequence that 
they have no degree of intellect, no memory, judgement 
or free will; but are guided in every respect by instinct 
and spontaneous impulses,—that they are incapable of 
instruction, and can superadd no acquired habits to those 
which are instinctive and inbred®. This consequence 
would certainly necessarily follow, was their nervous 
system perfectly analogous to the sympathetic of warm- 
blooded animals. But when we come to take into conside- 
ration the functzuns that in insects this system confessedly 
discharges, we are led to doubt very strongly the correct- 
ness of the assumption. Now in these animals the system 
in question not only renders to the nutritive and repro- 
ductive organs, which is the principal function of the great 
sympathetic nerves in the vertebrates; but by the com- 
mon organs maintains a connexion with the external 
* Vou. ILI. p. 664. 671. 
b N. Dict. d'Hist. Nat. ii. 47—. v. 592. xvi. 308—. 
