542 
MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
Perhaps it may at first appear doubtful whether this be really the case, since the large 
cerebral ganglia which give origin to the principal nerves of sense in Invertebrata 
are situated above the oesophagus towards the dorsal surface of the animal, while the 
cords themselves, and the ganglia which give origin to the nerves of motion and 
sensation simply, as well as those which supply the organs of manducation, are 
situated below it, along the ventral surface of the animal. Upon close examination 
it will be found that when the motor column in passing from the thorax to the head 
has arrived at the crura which descend from the brain on both sides of the oesophagus, 
it appears to wind round to the outer surface and unite with the base of the antennal 
nerves, where the column appears to terminate. It is in the median line above and 
between the two double cords that the transverse nerves originate ( b ), as described 
in my former paper ; and these also unite with the nerves to the antennse by very 
small filaments. This inclines me to consider them as forming part of one great 
system of nerves, which are more of an involuntary than of a voluntary character. 
Of this great system the sympathetic nerves doubtless form a part, of which the 
transverse nerves perhaps may be only a peculiar modification. It is a remarkable 
fact, that while the muscles of the wings are supplied with nerves which in every stage 
of the insect’s existence originate by double roots, one of which is derived from the 
motor tract of the cords before it arrives at a ganglion, and the other both from a 
ganglion of the sensitive tract and from the motor tract which passes over it, they 
are also supplied with large nerves from the transverse series, as may be best seen in 
the larva, long before the organs unto which they are given are called into activity. 
But this is not the case with the muscles of the legs, which are supplied only with 
very minute filaments from the transverse series, in addition to their compound or 
moto-sensitive nerves. The reason for this difference in the distribution of the nerves 
to the wings and legs is clearly on account only of their difference of function, the 
wings being more directly concerned than the legs in the acts of respiration. Pro- 
fessor Muller* has recently thrown out some valuable hints with regard to the nature 
of these transverse nerves ; he seems to consider them as peculiar nerves which com- 
bine the animal with the organic functions, not distinctly sympathetic nerves nor 
nerves of entirely voluntary motion. I am greatly inclined to lean to this opinion. 
It is evident that they are not simply the sympathetic system, because they are given 
so much to the muscles and tracheal vessels, while but very few filaments go to the 
viscera. I am less inclined to regard these nerves as the analogues of the true sym- 
pathetic, on account of their great size in certain insects, and because also it has 
been stated by De SerresT and Dr. Grant* that a series of ganglia exists on each 
side of the alimentary canal, which appears to be independent of the transverse nerves. 
I must acknowledge, however, that I have been unable to trace this series beyond the 
* Muller’s Archiv fur Anatomie, &c., No. 1. 1835, pp. 81, 84. 
f Paper on the Sympathetic Nerves of Insects. 
I Lecture on Comparative Anatomy. Lancet, 1834, vol. ii. p. 515. 
