278 CLASS VIII. 
single nerve, lying above upon the strings of the ganglionic nervous 
system, connects each plexus with the following one. In perfect 
Insects this system is less distinctly visible, and often is completely 
combined with the rest of the nervous system}. 
There is found in addition still another nervous system in Insects, 
destined especially for the organic life, which was made known in 
part by the investigations of SWAMMERDAM and LYONET in former 
times, and described by the last under the name of nerf recurrent?, 
and to which in our century Jon. MUELLER has by his investiga- 
tions especially directed the attention of anatomists. It has been 
compared by him and by most modern writers to the sympathetic 
nerve of vertebrate animals, by others to the nervus vagus. This 
system of nerves consists of a single middle portion and of two lateral 
portions. The single portion arises from one or more nervous 
ganglia situated in the head, which are connected with the most 
anterior part of the first (the cerebral) ganglion of the ganglionic 
cord. Irom this single portion whilst situated in the head nerves 
arise for the uppermost oral organs, and a thread which runs along 
the cesophagus on the dorsal surface to the stomach, and at its 
extremity terminates in a ganglion. In Phasma ferula BRANDT 
saw numerous branches arising transversely, and running in arches 
over the cesophagus and stomach to form a fine nervous net. Per- 
haps a similar distribution may be suspected in other Insects, where 
the extreme delicacy of the nervous branches does not permit their 
determination. In most Insects the middle single portion is the 
most developed ; in Gryllotalpa and Giryllus, on the contrary, the 
lateral portions are more developed than the single and middlemost. 
The lateral portions consist ordinarily of two pair of ganglia that 
lie close together behind the cerebral ganglion, of which the 
anterior is connected with the cerebral ganglion by one or two fine 
nervous threads. From these ganglia delicate nervous branches 
arise which run to the cesophagus whilst they are also in connexion, 
by fine threads with the single middle nerve that runs over the 
cesophagus’®. 
1 Besides the authors cited comp. also especially an excellent paper on the nervous 
system of Beetles by E. BhancHarp, Ann. des Sc. Natur., 3ieme Série, Tom. Vv. 
Zoologie, 1846, pp. 273—379, Pl. 8—15. . 
2 Traité anat. de la Chen. pp. 413, 578, &e. 
3 Comp. Jou. MuEtuER, Ueber ein eigenthiimliches dem Nervus sympathicus analoges 
