INSECTS. pari 
system of the great sympathetic nerve. It is impossible to recognise 
the position on the dorsal surface as such a character; for the reversed 
position of the heart in the invertebrate animals might lead us rather 
to expect that that of the central nervous system would be reversed 
also. The peculiarity of the sympathetic system, amongst other things, 
consists in this, that it supplies nerves which are distributed to parts 
not subject to the will. But since from the ganglionic cord in Insects 
the nerves of the organs of sense and the nerves of the voluntary 
muscles arise, there is no reason for comparing it to the sympathetic 
nerve. The ganglia therefore of this cord are to be considered as 
an union of the ganglia of the spinal nerves of the two sides!. This 
view would seem to receive more support when we reflect, that the 
spinal ganglia belong to the uppermost (the posterior) or the sensi- 
tive roots of the spinal nerves, and that in Insects two strings have 
been discovered in each connecting band between the ganglia, of 
which the undermost alone is connected with the gangla, whilst 
the uppermost merely passes with its fibres over the ganglion’. 
That here the uppermost and not the undermost string, as in the 
spinal cord of vertebrate animals, is related to motion, is to be 
explained by the reversed position of the nervous system. ‘The 
similarity becomes obvious when we thus consider the matter, that 
in Insects as well as in vertebrate animals the motor strings are 
placed towards the interior, the sensorial nearest to the surface. It 
is, however, perhaps more prudent not to pursue this analogy too 
far. With these uppermost strings we must not confound the 
system of transverse nerves which LyoneT described long ago in the 
caterpillar of the Willow-hawk under the name of brides épiniéres®. 
These are situated a little in front of each ganglion, pass transversely 
over the straight muscles which le lengthwise on the ventral 
surface, and are distributed by their branches to the muscles and 
especially to the air-tubes and the dorsal vessel. A longitudinal, 
1G. R. Treviranvs, Biologie, v. s. 331, 332; E. H. WEBER, Anat. comparata 
nervi sympathici, Lips. 1817, p. 95. 
2 This important discovery of NEwrort, who was incited to it by C. BELL, the 
celebrated discoverer of the distinction of the motor and sentient roots of the spinal 
nerves, may be seen, illustrated by figures, in Phil. Trans. 1834, Pt. 2, pp. 406—410. 
3 Traité anat. de la Chen. pp. 98, 201, Pl. rx. figs. 1, 2. Newport has very 
accurately investigated this nerve in Sphinw Ligustri, Phil. Tras. 1836, Pt. 1. 
pp. 544, 545, Pl. xxxvir. (This figure is transferred to Topp’s Cyelop. 11. p. 987.) 
