400 MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRT. 



around it. The ganglion at the union of the roots of this nerve distributes a few fila- 

 ments from its anterior surface, forwards upon the palate, and apparently also to the 

 extremity of the dorsal vessel, which, after passing along the oesophagus beneath the 

 brain, here divides into several trunks. Two of these pass downwards, one on each side 

 the oesophagus, to the proboscis, others outwards, and others upwards, to the eyes, 

 antennse, and front part of the head. Behind the brain, within the region of the head, 

 the vagus is connected by a branch on each side with the anterior lateral ganglia (g), 

 which are also connected with the superadded or transverse series (c) . The constancy 

 of its existence, and the situation and distribution of the vagus, in insects, are points 

 of deep interest for consideration. I have never found it in any other situation 

 than that which it occupies in the Sphinx ligustri. These are positive indications 

 of the analogy it bears to the great pneumogastric nerve in Vertehrata *. It is clear 

 that it ministers to a very important function, the involuntary motions of the stomach 

 and alimentary canal, which are as distinct and as constant as in the Vertehrata. Yet 

 we find an exceedingly large ganglion at its origin (e) ; and the remains of this gan- 

 glion may be traced upwards through fishes, reptiles, and mammalia, to man himself, 

 in whom we have it remaining only as a slight enlargement. What, then, is the office 

 of this ganglion ? Does it communicate sensation to the parts, or is the ganglion 

 merely a great centre of nervous energy, ministering to the involuntary functions of 

 the alimentary canal, the place of which in the higher animals is probably supplied 

 by a more perfect development of the sympathetic system ? The interest of this con- 

 sideration is increased, from the circumstance, that even while the insect is in some 

 of its earlier stages, before there is a complete approximation of the lateral cords and 

 ganglia of the body, and even previous to the development of the organs of loco- 

 motion, as in the Bee, the ganglion of the vagus is nearly as perfect in form as when 

 the insect has passed through all its changes. In the maggot or larva of the Wild Bee, 

 {Anthophora retiisa, Kirby,) where the whole of the nervous system is exceedingly trans- 

 parent, the ganglion is as complete as in the more organized and active caterpillars, 

 and the same is the case in the larva of Chrysomela tenehricosa, Linn., and other species. 

 In the latter insect it distributes several branches posteriorly to the sides of the oesopha- 

 gus and pharynx, [Plate XIII. fig. 4. (c, c),] besides the nervous trunk {d), which passes 

 backwards to the stomach, and which in its course becomes somewhat enlarged {h). 

 In the perfect insect of the same species [fig. 5.], its form and situation are the same. 

 In the same insect we have also remaining the nerves of taste (e, e). The general figure 

 of -the ganglion of the vagus is heart-shaped, or triangular, with the apex directed 

 backwards ; but in the ground beetle, Carahus, Linn., it is elongated oval,' lying trans- 

 versely above the palate. It is interesting to remark that the vagus always originates 

 from the crura, immediately below the cerebral ganglia or brain ; and even in Crustacea 

 we find it still arising from the crura [Plate XVII. fig. 40. (d, d)]. Now from this uni- 

 formity of origin, its possessing a ganglion, and its distribution to an organ endowed 



* Philosophical Transactions, 1832, p. 386. 



