THE SYMPATHIC SYSTEM. 2c./ 



which originates oft each side by one branch from the posterior portion 

 of the cerebrum running down the oesophagus, and giving off here and 

 there fine auxiliary branches to the single nervous cord. Both stand 

 in a certain reciprocal relation to each other, in so far as where the 

 double system preponderates the former diminishes, and where the 

 single cord is considerably developed the double ganglia with their 

 branches shrink up. 



The single nervous cord is considerably most developed in the 

 Coleoptera, Lepidoptera, and Libellulae. It here originates with two 

 branches arched towards each other, springing from the anterior por- 

 tion of the cerebrum, contiguous to the nerves of the antennae. Both 

 branches unite at the centre, and form a small ganglion (ganglium 

 frontale], and from this the single nerve proceeds beneath the brain 

 (PI. XXXII. f. 6 8. a, a.). This, from its bending form, Swam- 

 merdam and Cuvier called the nervus recurrens. The arch is some- 

 times double, as in the silkworm (PI. XXXII. f. 6 and 7.). In the 

 Coleoptera, on the contrary, always simple (the same, f. 8.) ; but yet 

 in both finer branches originate from this arch, which sink to the 

 anterior wall of the oesophagus, and pass even into the labrum. In 

 some Coleoplera, for example, Melolontha, these arching branches are 

 so fine that they even escaped the accurate Straus ; he detected but two 

 delicate filaments to arise from the frontal ganglion, lying in front of 

 the cerebrum, which appeared to bend about the oesophagus. I also 

 have not been able distinctly to perceive in several beetles this con- 

 nexion of the frontal ganglion with the cerebrum. When the filament 

 has passed behind the brain it runs along" the oesophagus as a simple 

 cord, which nevertheless gives off everywhere very delicate auxiliary 

 branches to the tunics of the oesophagus, as far as the stomach, and 

 here divides itself into two equal branches, forming at the point of 

 division a small ganglion, from which, besides the two main stems, 

 many other smaller filaments proceed. Where the stomach commences 

 in the craw, consequently in the predaceous insects, and at the ante- 

 rior half of the large simple stomach in the vegetable feeders, its last 

 very delicate branches terminate, for they sink between the tunics of 

 the stomach, and there lose themselves ; indeed, in the cases in which 

 the oesophagus is tolerably long, they but just reach the stomach itself, 

 without spreading themselves over it. This description of the dis- 

 tribution of the single nervous cord will suit also the Lepidoptera, 

 for in them also it never extends beyond the commencement of the 



