MR. NEWPORT ON THE RESPIRATION OF INSECTS. 
545 
as will presently be shown, with a branch from the great moto-sensitive nerve. This 
union is exceedingly interesting, and proves that some of the nerves, at least, termi- 
nate in loops, which unite with portions of other nerves, according to the views of 
some of the German physiologists. The fourth branch also is an exceedingly inter- 
esting one, from its uniting in a similar manner with a branch from another moto- 
sensitive nerve. It is composed of fibres which are approximated to those of the 
transverse trunk, some of which passing from without inwards, and others from within 
outwards, form a little triangular plexus (i), similar to the one before described, and 
then unite to form the fourth branch of the transverse nerve. This branch passes 
directly forwards along the inner margin of the great rectus, and having arrived at 
the insertion of the muscle, it gives off a filament, which, dividing again into two por- 
tions (j), passes directly outwards, and is given to the greater recti at their insertion. 
The nerve then passes forwards to the external margin of the greater oblique, unto 
the lower portion of which it gives many filaments, and also to the second and third 
oblique, and to the triangularis, and then unites with the second, or inner division of 
the second pair of moto-sensitive nerves of the cord ( k ) in the preceding segment. 
The fifth branch of the transverse nerve passes off from the trunk a little more ex- 
ternally (/), and is given to the visceral surface of the greater rectus, and to some 
large tracheae which are distributed over it. The transverse nerve then gives off a 
few small branches to the rectus, while its main trunk passes outwards until it arrives 
at a tuft of tracheal vessels which arise from the longitudinal trachea opposite to a 
spiracle (m). It then divides into two principal branches, one of which passes on 
each side of these tracheae, giving off many branches. Some of these from the ante- 
rior branch pass inwards along the course of the tracheae towards the alimentary 
canal, others forwards to the transverse lateral muscles, unto which they give fila- 
ments, and others upwards to the dorsal recti, unto which they are also distributed, 
while some of their ultimate branches appear to be given to the dorsal vessel. The 
posterior division of the nerve in like manner gives filaments to the tracheae which 
arise opposite to the spiracle. A small branch joins with the trunk of the great 
moto-sensitive nerve ( n ), which crosses the trachea posterior to the spiracle. Another 
branch passes backwards, and dividing into several branches is given to the lateral 
oblique and lateral rectus muscles (o), and a fourth set passes onwards along the 
visceral surface of the dorsal rectus and to the dorsal vessel. 
All the muscles unto which these nerves are distributed, besides being concerned 
in respiration, are necessarily concerned in the voluntary motions of the insect, and 
consequently it is necessary that they should be supplied with voluntary nerves, as 
well as with those just described, which are presumed to be of mixed function. This, 
it will be seen, is actually the case. 
The first or chief pair of nerves from the moto-sensitive columns in each seg- 
ment ( f ), is composed of one portion from the ganglion of the sensitive tract, and 
one from the motor which passes over it, and, after receiving a small filament from 
4 A 
mdcccxxxvi. 
