INSECTS. 277 



ystem of the great sympathetic nerve. It is impossible to recognise 

 le position on the dorsal surface as such a character ; for the reversed 

 osition of the heart in the invertebrate animals might lead us rather 

 expect that that of the central nervous system would be reversed 

 o. The peculiarity of the sympathetic system, amongst other things, 

 onsists in this, that it supplies nerves which are distributed to parts 

 ot subject to the will. But since from the ganglionic cord in Insects 

 le nerves of the organs of sense and the nerves of the voluntary 

 mscles arise, there is no reason for comparing it to the sympathetic 

 erve. The ganglia therefore of this cord are to be considered as 

 n union of the ganglia of the spinal nerves of the two sides 1 . This 

 iew would seem to receive more support when we reflect, that the 

 )inal ganglia belong to the uppermost (the posterior) or the sensi- 

 ve roots of the spinal nerves, and that in Insects two strings have 

 een discovered in each connecting band between the ganglia, of 

 r hich the undermost alone is connected with the ganglia, whilst 

 le uppermost merely passes with its fibres over the ganglion 2 , 

 t here the uppermost and not the undermost string, as in the 

 )inal cord of vertebrate animals, is related to motion, is to be 

 xplained by the reversed position of the nervous system. The 

 milarity becomes obvious when we thus consider the matter, that 

 Insects as well as in vertebrate animals the motor strings are 

 Laced towards the interior, the sensorial nearest to the surface. It 

 , however, perhaps more prudent not to pursue this analogy too 

 ar. With these uppermost strings we must not confound the 

 ystem of transverse nerves which LYONET described long ago in the 

 aterpillar of the Willow-hawk under the name of brides Spinieres 3 . 

 ^hese are situated a little in front of each ganglion, pass transversely 

 ver the straight muscles which lie lengthwise on the ventral 

 urface, and are distributed by their branches to the muscles and 

 specially to the air-tubes and the dorsal vessel. A longitudinal, 



1 G. R. TREVIRANUS, Biologic, v. s. 331, 332; E. H. WEBER, Anat. comparata 

 vrvi sympathici, Lips. 1817, p. 95. 



2 This important discovery of NEWPORT, who was incited to it by C. BELL, the 

 elebrated discoverer of the distinction of the motor and sentient roots of the spinal 

 erves, may be seen, illustrated by figures, in Phil. Trans. 1834, Pt. i, pp. 406 410. 



3 Traite anat. de la Chen. pp. 98, 201, PI. IX. figs, i, 2. NEWPORT has very 

 ccurately investigated this nerve in Sphinx Ligustri, Phil. Trans. 1836, Pt. II. 

 P- 544; 545, PL xxxvii. (This figure is transferred to TODD'S Cyclop. II. p. 987.) 



