544 
MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
corresponding - ganglia and vagus in Vertebrata. The vagus nerve then passes along 
the median line of the oesophagus in close relation with the anterior or aortal portion 
of the dorsal vessel, which may be looked upon as the two carotids of Vertebrata 
united. The nerve lies between this portion of the vessel and the oesophagus, as 
between the carotids and lateral parts of the oesophagus in Vertebrata. A little be- 
fore the vagus arrives at the cardiac portion of the stomach in insects it divides again 
into two parts, and very often at its point of division again forms a ganglion. This 
is the case in the Meloe, Linn., and some other genera. These two parts are divided 
into many others, which are distributed over the sides of the stomach, so that even 
in its ultimate distribution in insects the nerve still bears analogy to its distribution, 
and its division into many branches around the oesophagus and cardiac extremity of 
the stomach in Man and the higher Vertebrata. In Crustacea the nerve closely re- 
sembles that of insects, but approaches even nearer in its resemblance to that of Man. 
It is given almost entirely to the stomach, at the cardiac portion of which it forms a 
ganglion, and then divides into two branches, each division being subdivided into 
four portions, which are distributed around the stomach. Only a few filaments from 
these portions unite with some very fine nerves, which probably are the sympathetic, 
and which are given to the highly developed liver in these animals. 
The minute distribution of the transverse and moto-sensitive nerves deserves par- 
ticular attention. It is known that a ganglion exists in the sensitive tract of the 
cords in each segment, and that immediately anterior to this ganglion, on the dorsal 
surface of the cords, there is also a set of the transverse nerves (c). Each set of 
transverse nerves at the point of divergence from its longitudinal portion, which lies 
above and between the cords, forms a triangular plexus ( b ), in which the transverse 
fibres are observed to be continuous from one side of the body to the other, joined by 
the longitudinal ones, and thus form the plexus. The first branch from each set or 
plexus of transverse nerves is very small, and passes, as formerly described*, over the 
outer margin of the next ganglion (a), and then converging to the median line unites 
with its fellow of the opposite side to form the longitudinal tract ( d ), after each fibre 
has received a few filaments from the upper or motor surface of the cords. Hence 
these nerves are of mixed character, and contain some voluntary motor fibrils. The 
second branch of the transverse nerves (e) is given off on the inner side of the smaller 
rectus, and unites with the moto-sensitive nerve from the ganglion and motor tract 
of the cords (/'). The transverse nerve then passes diagonally outwards and forwards 
over the smaller rectus, near the external margin of which it gives off its third 
branch (g) ; this passes at first forwards and outwards until it arrives at the inser- 
tion of the preceding small rectus. It then passes along the upper surface of the 
middle of the rectus, unto which it distributes minute branches, until it arrives at 
about the middle of the muscle. It then sends forward a small branch to the ante- 
rior extremity of the muscle (A), while its main trunk bends directly inwards to unite 
* Philosophical Transactions, Part II., 1834, p. 410. 
