INTERNAL ANATOMY OF INSECTS. 17 
are sometimes interwoven with the muscles, as the woof 
with the warp in a piece of cloth a ; those from the three 
or four first commonly rendering to the muscles of the 
legs, wings, and other parts of the trunk, and those from 
the remainder to the abdomen. After their origin they 
often divide and subdivide, and terminate in numerous 
ramifications that connect every part of the body with 
the sensorium commune. A -pair of nerves is the most 
usual number that proceeds from each side of a gan- 
glion b ; but this is by no means constant, since in the 
louse, the hive-bee, and several other insects, only a single 
nerve thus proceeds e ; and in the larva of Ephemerce, 
while two pairs issue from the six'Jirst ganglions, only a 
single one is emitted by the Jive last d . In the spinal mar- 
row of the rhinoceros-beetle, both larva and imago, the 
nerves consist of simple filaments which diverge like rays 
in all directions e : the same circumstance distinguishes the 
cheese-maggot, only some of the nerves appear to branch 
at the end f : in the louse, the last ganglion sends forth 
posteriorly three pairs of nerves which render to the 
abdomen g . Sometimes, though rarely, nerves originate 
in the internodes of the spinal marrow. Cuvier indeed 
has asserted that in invertebrate animals all the nerves 
spring from the ganglions, and never immediately from 
the spinal marrow ; but Swammerdam, in describing 
those of the silk-worm, mentions and figures four pairs 
as proceeding from the four anterior internodes, exclud- 
a Cuv. itbi supr. 349. b Lyonet Anat. t. ix. x. 
8 Plate XXI. Fig. 8. Swamm. Bibl. Nat. t. xxii./. 6. 
d Ibid. t. xv. /. 6. ' Plate XXI. Fig. 7. 
f Swamm. ubi supr. t. xliii./. 7- h, h. 
* Plate XXI. Fig. 8. 
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