LESSON 75.] NERVOUS SYSTEM IN INSECTS. 247 



If a small pipe be tied in the heart, and injection (size colored 

 with vermilion) be thrown in, these so-called nerves will be demon- 

 strated as arteries. If the same experiment be made from the heart 

 (dorsal vessel) of a caterpillar, the like results will be obtained, and thus 

 establish the true character of this structure in Insects, Myriopods, 

 and the lower Crustacea, and demonstrate beyond all doubt that the 

 so-called motor, and respiratory nerves, in all these animals, are a 

 system of arteries. Being always filled, however, with white, coagu- 

 lated blood, in death, the main trunk from which the branches are 

 distributed lying upon the upper surface of the gangliated nervous 

 chord, and exceedingly minute and attenuated in structure, they 

 much more resemble nerves than arteries. 



LESSON LXXV. 



NEKVOUS SYSTEM OF INSECTS, CONTINUED; 



1119. The individuals composing the articulate sub-kingdom 

 have their bodies divided into a series of more or less distinct rings, 

 or segments, arranged in a linear series. This disposition is more 

 apparent in those animals which exhibit lowly organization, that 

 is to say, the Worms, Myriopods, and the larval condition of In- 

 sects. 



1120. Carefully examined, it will be seen that in structure, in- 

 ternally, these segments present merely a repetition of parts, and 

 this statement is equally true of the nervous system. 



1121. In the centre of each segment of a Centipede,.OT a caterpil- 

 lar, a nerve-knot or ganglion is invariably found ;, from this nervous 

 centre the muscles of the segment obtain their supply of nervous im- 

 pulse ; the only exception to this rule is in regard to the superior 

 portion of the brain the supra-oesophageal ganglion where we find 

 the nerves solely distributed to the organs of special sense, and to 

 the development of the frontal ganglion, from whence the sympa- 

 thetic nerves arise. An illustration is given of the nervous system 

 of the caterpillar of the Goat Moth, Cossus ligniperda (Fig. 370), 

 copied from an original preparation. 



1122. The bilobed ganglion, having a long transverse diameter 

 (a), is the supra- cesophageal ganglion, or brain ; the nerves dis- 



