OF INSECTS. 
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nerves in pairs, which visit all the principal organs, 
and ramify in all directions. 
The nervous system may be considered under two 
divisions, the ganglionic central cord, with its branches, 
and the nervous system of the esophagus and stomach. 
The former is the analogue of the spinal marrow, 
and the latter of the great sympathetic nerve. 
The ganglionic cord extends from the head to the 
hinder extremity, is situate beneath the intestinal 
canal, and runs along the ventral face of the body ; 
(PI. II. fig. 1, g, h , i, l y /.) This presents knotty 
expansions or ganglia at intervals throughout its whole 
course. Two of these are placed in the head, one 
above the esophagus near the pharynx, the other 
beneath it, and, considered collectively, they form 
what many authors have denominated the brain, 
(cerebrum and cerebellum of Burmeister.) The an- 
terior of these cephalic ganglia, (the cerebrum,) lies 
transversely, and is usually more or less distinctly 
divided into two hemispheres. It emits a nerve to 
each of the antennae, also the optic nerves, and lateral 
branches which unite it to the posterior cephalic 
ganglion. The optic nerves spring from the outer 
margin of each cerebral lobe, and are generally broad 
at the base and narrower at the extremity terminating 
in the eye. Their base is sometimes as wide as the 
lobes themselves, and in certain cases they are broader 
at the extremity than any part of the cranial ganglion. 
The optic nerves of the stemmata likewise originate 
from the same source, sometimes in single filaments, 
at other times divided near the extremity. After the 
