NERVOUS SYSTEM. 297 



deflexed, so as to surround the oesophagus, forming a kind 

 of nervous collar. From the thoracic and abdominal ganglia 

 are emitted nerves which communicate with the legs, \\ings, 

 and other organs of the body. In the larva of the goat- 

 moth, Lyonnet counted forty-five pairs of these nerves, 

 besides two single ones, thus making a total of ninety-two, 

 which is considerably more than are found in the human 

 body, namely, seventy-eight. 



In the vertebrated animals the nerves proceed from the 

 brain, which is inclosed in the head ; in insects, on the con- 

 trary, we have seen that nerves proceed from the various 

 knots, whether belonging to the head, thorax, or abdomen ; 

 hence we might analogically call the various ganglia and 

 their connecting filaments an elongated brain. In the verte- 

 brated animals sensation originates in the brain ; and hence, 

 from the concentration of this organ into one mass (for so 

 we may call it, although divided into two lobes), sensation 

 is more concentrated, and the feelings rendered highly acute. 

 In insects, on the contrary, owing to the want of concentra- 

 tion of the nervous ganglia, sensation is necessarily much 

 less acute; and, as the nerves laterally emitted by one gangUon 

 generally serve for the segment of w^hich it forms a part, the 

 connexion with the preceding or subsequent gangha being at 

 the same time slight in proportion to the slightness of the 

 connecting filaments, we are enabled satisfactorily to account 

 for the apparent want of sensation in insects, as exhibited, 

 for instance, by the cockchafer, which will walk about, al- 

 though some bird has nearly emptied the body of its viscera; 

 or by the head or abdomen of a wasp, which will continue to 

 bite or sting long after they have been separated from the 

 rest of the body ; or by the headless trunk of a male mantis, 

 which has been known to unite itself to the other sex, as re- 

 corded by Dr. Smith, and quoted by Kirby and Spence. 

 Another instance is recorded by the Rev. Mr. Bird, in a 



