588 Analysis of Books, 8fc. 



the brain and spinal marrow. The characters derived from form 

 and position are so little determinate, that the visceral (sympathetic) 

 nerve of insects is usually single, whilst in vertebral animals it is 

 double ; that the spinal marrow of insects, on the contrary, for the 

 most part, is formed of separate cords, whilst it is solid in vertebral 

 animals ; that the sympathetic nerve of insects is situated on the 

 back, and the nervous system of voluntary motion (spinal marrow) 

 is placed on the abdominal aspect ; that in articulata, this same 

 system is knotted, and in fishes a solid cord ; the sympathetic, in 

 the one case, swelling into ganglia, which, in the other, (fishes,) as 

 already mentioned, are deficient. 



If due attention had been paid to the statements of Swammerdam 

 and Lyonnet, the abdominal chain of ganglia in insects could never 

 have been assimilated to the sympathetic nerve of vertebral animals. 

 Under the name of Nervus Recurrens, the former has described in 

 the larva of the rhinoceros-beetle and of the silk-worm, a nerve 

 arising by two roots from the anterior part of the cerebral ganglion : 

 these roots, after proceeding a little way forwards, turn backwards 

 and approximate to each other, uniting into a ganglion placed above 

 the commencement of the esophagus ; from this proceeds the 

 recurrent nerve ; which, after having passed through a second 

 ganglion, runs along the posterior surface of the resophagus, to be 

 distributed upon the stomach and intestine. The recurrent nerve of 

 the larva of the rhinoceros-beetle is represented in Tab. xxviii. fig. 2, 

 and that of the silk-worm in Tab. xxviii. fig. 3. g. of the Biblia 

 Nature. 



Lyonnet's description of this nerve in the larva of the Phalcena 

 cossus is still more accurate. It here begins with a series of ganglia 

 in the anterior part of the head, above and in front of the brain. The 

 third of these ganglia, reckoning from before backwards, is the largest, 

 and is connected by two sets of lateral cords with cerebral nerves, 

 and by a branch on each side with the ganglion in front of it, which 

 again gives origin to a single filament, by means of which it com- 

 municates with the first and anterior of these three frontal ganglia. 

 The nerves derived from these ganglia are distributed upon the 

 oesophagus. The third ganglion, after a short space, is continued 

 into a fourth, to which again succeed several smaller ones. The 

 nerve thus formed, about the middle of the head, perforates the 

 dorsal vessel from above downwards, running between it and the 

 oesophagus, distributing its branches to the surrounding parts, and 

 terminating by dividing into two portions, which are lost in the sub- 

 stance of the stomach. (Lyonnet, Traite Anatomique de la Chenille, 

 &c. Tab. xii. fig. 1., xiii. fig. 1., xviii. fig. 1.) 



This nerve has been incidentally noticed by Cuvier in the rhino- 

 ceros-beetle's larva, \n Hydrophilus piceus, and Locusta viridissima; 

 by Meckel in the common Cicada; by G. Treviranus in Dytiscus 

 marginalis, Sphynx ligustri, and the common bee ; and by Marcel 

 de Serres, though very incorrectly, in some species of acheta. 



The character and functions of this remarkable nerve are points 



