312 FUNCTIONS OF THE CORD. 



of a truly rational character. When we attentively consider the habits 

 of these animals, we find that their actions, though evidently directed to 

 the attainment of certain ends, are very far from being of the same spon- 

 taneous nature, or from possessing the same designed adaptation of means 

 to ends as those performed by ourselves, or by the more intelligent ver- 

 tebrata under like circumstances. We judge of this by their unvarying 

 character, the different individuals of the same species executing pre- 

 cisely the same movements when the circumstances are the same, and 

 by the very elaborate nature of the mental emotions which would be re- 

 quired in many instances to arrive at the same results by an effort of 

 reason. Of such we can not have a more remarkable example than is 

 to be found in the operations of bees, wasps, and other social insects, 

 which construct habitations for themselves upon a plan which the most 

 enlightened human intelligence, working according to the most refined 

 geometrical principles, could not surpass, but which yet do so without 

 education communicated by their parents or progressive attempts of their 

 own, and with no trace of hesitation, confusion, or interruption, the dif- 

 ferent individuals of the community all laboring effectively to one pur- 

 pose, because their automatic impulses (producing what are usually term- 

 ed instinctive actions) are all of the same nature. 



" Not only are the locomotive ganglia multiplied in accordance with the 

 repetition of segments and members, but the respiratory ganglia are mul- 

 tiplied in like manner in accordance with a repetition of respiratory or- 

 gans. The respiratory division of the nervous system consists of a chain 

 of minute ganglia lying upon the larger cord, and sending off its delicate 

 nerves between those that proceed from the ganglia of the latter, as seen 

 in Fig. 151. These respiratory ganglia and their nerves are best seen in 

 the thoracic portion of the cord, where the cords of communication be- 

 tween the pedal ganglia diverge or separate from one another ; and this 

 is particularly the case in the pupa state, when the whole cord is being 

 shortened and their divergence is increased. The thoracic portion of the 

 cord is shown in Fig. 152, B, which represents the second, third, and 

 fourth double ganglia of the ventral cord, the cords of connection between 

 them here widely diverging laterally, and the small respiratory ganglia 

 which are connected with each other by delicate filaments that pass over 

 Fig. 151. the ganglia of the ventral cord, and which send off lateral 

 branches that are distributed to the air-tubes and other 

 parts of the respiratory apparatus, and communicate with 

 those of the other system." 



Illustrations of the nervous system of the articulata. 

 Fig. 151, A, single ganglion of centipede, much enlarged, 

 showing the distinctness of the purely fibrous tract, b, from 



Ganglion of centi- ,-\ . . -, -y-j. ., _,- -pj . / .1 



pede. the ganghonic column, a. Fig. 152, B, portion of the 



