INTERNAL ANATOMY OF INSECTS. 3 
the will and of the intellect, is confined to the internal orga- 
nic life, its agency continues uninterrupted during sleep, 
and is subject to no paralysis. While the former is the 
seat of the intellectual powers, the latter has no relation 
to them, but is the focus from whence instincts exclu- 
sively emanate: from it proceed spontaneous impulses 
and sympathies, and those passions and affections that 
excite the agent to acts in which the will and the judge- 
ment have no concern?. 
It is probable, though the above appear to exhibit 
the primary types of nervous systems, that others ex- 
ist of an intermediate nature, with which future investi- 
gators may render us better acquainted: but as our bu- 
siness is solely with that upon which sects in this re- 
spect have been modelled, without expatiating further in 
this interesting field, I shall therefore now confine myself 
to them. 
We have before seen® that the nervous system of in- 
sects belongs to the ganglionic type: but it requires a 
more full description, and this is the place for it. It ori- 
_ginates in a small brain placed in the head, and consist- 
ing almost universally of two lobes, sometimes extremely 
distinct. It is placed over or upon the @sophagus or gul- 
let, and from its posterior part proceeds a double ner- 
vous chord, which embracing that organ as a collar dips 
below the intestines, and proceeds towards the anus, form- 
ing knots or ganglions at intervals, in many cases cor- 
2 N. Dict. d’ Hist. Nat. xvi. 307. 
> Thus in the Mollusce there must be a great difference in this 
respect, since in some of these the brain or cerebral ganglion has 
been cut off with the head, and another reproduced. did, xvi. 306. 
Comp. v. 391. ¢ Vor. III. p. 29. 
