INSECTA. 



957 



vessel which we regard as connected with the 

 circulatory system, as we shall hereafter show. 



As nerves of organic function, we have now 

 to consider those which are especially given to 

 the different internal organs, and not to the 

 voluntary muscles. Having already considered 

 the transverse nerves, which are distributed so 



especially to the respiratory organs, as nerves of 

 mixed character, those which we regard more 

 especially under the above designation are the 

 sympathetic and the vagus or visceral nerves. 

 The sympathetic, or anterior lateral ganglia 

 (fig. 415, C), are situated two on each side of 

 the oesophagus behind the brain, and anterior 



Fig. 415. 



Brain and nerves of the head and first segment of a pupa of Sphinx ligustri. 



A, brain; B, optic nerves; C, anterior lateral or sympathetic ganglia; D, antennal 

 nerves ; E, frontal ganglion of the recurrent or vagus nerve. (Newport, Phil. Trans.) 



to the great muscles of the oesophagus and pha- 

 rynx. They are of considerable size, being 

 each about one-third as large as one-half of the 

 cerebrum, and they are connected with most of 

 the other nerves in the head. Thus, besides 

 their connexions (a) with the brain, one nerve 

 passes forwards beneath the optic nerves, and 

 joins with a minute lilament from the nerve to 

 the antennae, (g,) and also with one to the 

 mandibles, while another passing across the 

 oesophagus is united with the main trunk of the 

 visceral or vagus nerve (e), as it passes along 

 to the stomach, and another branch joins with 

 the first set of transverse nerves (A), while other 

 filaments passing outwards are distributed to 

 the muscles of the oesophagus and pharynx. 

 This latter fact, which we have most distinctly 

 ascertained in Meloe cicatricosus, a large species 

 well adapted both for an examination of this 

 and of the visceral nerve, is particularly inte- 

 resting from the circumstance that, after the 

 most careful examination, we could not find 

 any other nerve given to those muscles (fig- 

 416, C). We have observed a similar distri- 

 bution to the muscles of the oesophagus in Lu- 

 canus, and also in the Sphinx, so that from their 

 connexions we may justly conclude these gan- 

 glia to constitute at least a portion of the true 

 sympathetic system. From their relative situ- 

 ation they appear to be analogous to the supe- 

 rior cervical ganglia of the sympathetic in Yer- 

 tebrata. It is, however, an interesting fact, as 



noticed by Burmeister,* that these ganglia ap- 

 pear to be largest in some of those insects in 

 which the recurrent nerve which we have de- 

 scribed as the vagus is least developed. Thus, 

 as shown by Muller, Brandt, and Burmeister, 

 these ganglia of the sympathetic system have 

 a large size in the Orthoptera, and, instead of 

 being traceable scarcely beyond the region of 

 the head, send off one or two branches which 

 run along the sides of the oesophagus to a great 

 distance, while the recurrent or vagus nerve, 

 after uniting with these ganglia behind the 

 brain, appears to terminate or be lost in the 

 nerves that originate from them. In Gri/llus 

 migratorius, Burmeister has shownf that after 

 the recurrent nerve has formed a minute gan- 

 glion just behind the brain, and united with 

 the first of these sympathetic ganglia, it ap- 

 pears to terminate, while the same ganglion 

 sends off posteriorly two branches, which run 

 along the upper surface of the oesophagus, where 

 the external one forms a small ganglion, and 

 that the second, or most external of these ante- 

 rior lateral ganglia, also sends a large nerve 

 backwards, at the side of the oesophagus, as far 

 as the crop, where it forms a ganglion and 

 sends off nerves, and at the hinder part of the 

 crop a second ganglion, from which nerves are 

 given to the coecal appendages of the alimen- 



Op. cit. p. 288. 

 t Id. pi. xxxi. fig. 6. 



