610 
each other by sensitive columns. A tract has 
also been recently described by Mr. Newport,* 
pare along the dorsal surface of these co- 
mns, and giving off lateral nervous branches ; 
this has been regarded as a molar tract. Mi- 
nute anatomy has also unfolded to us what 
may be considered as the analogue of the re- 
Spiratory system of nerves, and a par vagum. 
ints we will now notice in detail, 
commencing with the Hemipterous Insecta, in 
which the nervous system is least precy or- 
po. In the perfect state of the Ranatra 
inearis the nervous system consists (besides 
the su phageal nervous socnmenieners 
of a small round ganglion (fig. 345, a), situa’ 
below the wsophagus at its very commence- 
Fig. 345. 
Ye 
Ventral nervous cord of Ranatra linearis (perfect 
state ), magnified to about twice the natural size. 
a, small round sub-csophageal ganglion. 6, 
large quadrilobate thoracic ganglion. ec, ¢, fila- 
ments passing down the lengthened abdomen. 
ment; from this two longitudinal commissures 
pass to join with a large quadrilobate ganglion 
()s situated at the further extremity of the 
orax. From each side of this ganglion there 
are given off three nervous threads, passing 
superiorly, transversely, and inferiorly; and 
from the lower of the ganglion, which is 
slightly fusiform in shape, there are given off two 
bundlesof most minute and delicate nervous fila- 
ments (cc), each containing five branches, which 
pass downwards into the lengthened abdomen to 
supply the parts situated in that region; there is 
also a supra-cesophageal nervous accumulation. 
In the Orthoptera the nervous system presents 
a certain d of concentration worthy of no- 
tice. In the perfect state of a species of 
* Philosophical Transactions for 1832 and 1834, 
NERVOUS SYSTEM. (Comparative Anatomy.) q 
_ the larva of the Oryctes nasicornis, 
Acrydium there are two comparatively large 
thoracic ganglia, very near each other, and 
connected, as usual, by commissures; in 
abdomen there are five ganglia of much smaller 
size, connected in a similar manner, and givin 
off lateral filaments: the first and secon 1 o 
these abdominal ganglia are some distance from 
each other; the three last are much mor 
closely approximated, and are rather larg 
and more distinct ; the cerebral ganglion is 
small size. we 
Proceeding with the Coleoptera, we find th 
many of the Lamellicornes, in their perfe 
state, have a singular and rather unusual m 
of developement of their nervous system; | 
ganglia are but few in number, closely approx 
mated, and the two posterior ones give off nume. 
rous radiating filaments: this is the case wi 
?- e 
to a dissection by Swammerdam.* In th 
Geotrupes stercorarius (fig. 346), 
Fig. 346. 
pe weieisy feta: He corar 
fect state), magnified to three tin 
natural size. ae 
a, bilobate thoracic ganglia. 6b, abdomi1 
glia. c, c, filaments to the intestine. d, 
state, another of the Lamellicorn 
found in the pss distinctly 
ganglia (a), connec ongituc 
aed and one ier nglion at t 
tion of the thorax with the abdom 
ately contiguous with which are + 
and three smaller ganglia, closely 
mated to each other B: the last. 
longest, of rather a fusiform shape, a 
off radiating nervous filaments, particule 
long branches to the abdominal visce 
adjacent parts (c,c). The more usua 
however, of the nervous system, is § 
will be described in the subsequent 
hT 
(i 
* Biblia Nature. 
