MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRI. 399 



not appear to give filaments to the muscles ; while the main branch (d) of the nerve 

 passes exterior to the tracheal vessels, and seems to be given chiefly to the flexor 

 muscles, which lie along the exterior of the organ. The course of the fourth nerve (c) 

 I have not distinctly traced ; it appears to run along the smaller flexor. Now there 

 are two pairs of nerves which exist in the larva, and come from the crura, near the 

 base of the cerebral ganglia, just below the origin of the pneumogastric, which I 

 have been unable to discover in the perfect insect. I suspect, therefore, that these 

 nerves, during the development of the insect, have united with the mandibular and 

 maxillary to form the large trunk to the proboscis. This appears probable, as I shall 

 presently show that coalescence of nerves actually does take place, and that the nerves 

 belonging to the suboesophageal ganglion are forced upwards during the development, 

 so as to appear as if coming from the lower part of the crura [Plate XIII. fig. 7.(1)] on 

 each side the pharynx. If this be correct, a question arises, What are their functions? 

 The larger branch given to the muscles, chiefly the flexors, is clearly analogous to the 

 great mandibular nerve of Fertehrata ; and it is not unreasonable to suppose that the 

 small branch which passes along the groove of the proboscis, where an exquisite 

 sensibility of taste is required, may be analogous to the gustatory, and in the larva 

 be one of those nerves which are distributed around the mouth and palate. This 

 opinion is further supported by the nerves originating in the larva just below the 

 pneumogastric, and above the suboesophageal, ganglion, which ganglion, in the 

 perfect insect, gives the nerve to the proboscis. Now this is in perfect accordance 

 with, and beautifully illustrates, the philosophic views of Sir Charles Bell, who has 

 shown that every portion of an organized being is supplied with an additional set of 

 nerves for every additional function it is required to perform. In the larva, the man- 

 dibles are hard and powerful, requiring, probably, little more than simple sensation 

 and motion. But in the perfect insect, the proboscis is delicate and flexible, and, 

 so far as we are enabled to judge, highly susceptible of impressions, one of which, 

 doubtless, is taste. 



II. 2. Nerves of Involuntary Function, 

 a. The Vagus, or Pneumogastric. — This nerve, the recurrent of Lyonet, originates 

 immediately above those nerves which seem to have united with the manducatory. It 

 has been shown to arise by two roots, [Plate XIII, fig. 3. (e),] one from each crus. These, 

 after passing forwards and uniting in a ganglion in the middle line above the palate, 

 run backwards, as a single trunk, [e, /,'] beneath the cerebral ganglia, the brain, be- 

 tween the dorsal vessel and oesophagus. Just at entering, and for a short distance 

 within the thorax, it gives off" filaments to the dorsal vessel [fig. 3. {h, ^)], while the main 

 trunk passes along the middle of the oesophagus, unto which it distributes filaments, 

 until it arrives at the cardiac portion of the stomach, [fig. 3. (/),] where it gives a 

 few filaments to the air-bag, or crop, and then divides into three branches, which run 

 along the middle and sides of the stomach, and are again subdivided and distributed 



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