Nervous System on the Resjnration of Insects. 281 



nervous system, and that this region in the Dytici corresj)onded 

 with the metathoracic centre or ganglion, the function of which 

 would be to excite the respiratory movements and to coordinate 

 and maintain them. On tlie other hand, he supposed the move- 

 ments of the posterior part of the abdomen connected with 

 respiration to be under the influence of the subojsophageal 

 gangUon. The abdominal ganglia, from which the respiratory 

 nerves originate, according to M. Faivre simply play the part of 

 conductors in relation to the respiratory centre or metatho- 

 racic ganglion : after the separation of the thoracic centres, they 

 cannot maintain respiration. 



Having for some time particularly directed my attention to 

 the comparative physiology of the nervous system, I was struck 

 with the results at which M. Faivre had arrived, and with their 

 comj)lete discordance both with the notions generally entertained 

 regarding the functions of the nervous system in the Articulata 

 and with the previous experiments of M. E. Blanchard upon the 

 nervous system of the Arachnida. I therefore resolved to take 

 up the question ; and as with Dyticus experimentation is diffi- 

 cult, and the results complex and consequently not very conclu- 

 sive, I selected as the subject of my investigations a far more 

 favourable insect, namely the larva of Libellula. 



This larva, as is well known, possesses a nervous chain formed 

 by a series of twelve ganglia, all perfectly distinct from each 

 other. In it the metathoracic ganglion is united with the first 

 abdominal ganglion by long connexions, enabling the two 

 ganglia to be easily separated : in it, also, the respiratory move- 

 ments are particularly easy of observation, betraying themselves 

 in two different manners — namely, in the first place, by move- 

 ments of depression and elevation of the inferior half-rings of 

 the abdomen, and, secondly, by the alternate separation and 

 approximation of the five appendages situated at the extremity 

 of the last segment. 



The following are the results of my experiments upon this 

 larva. In my first experiment, I cut away the head at noon : 

 respiration was continued with great regularity, twenty-six in- 

 spirations per minute being counted; at 6 o'clock p.m. the 

 respiratory movements were still strong and regular; at 9 o'clock 

 the next morning the respiration still persisted, although much 

 weakened, and it was not quite extinct until 3 o'clock p.m. 

 From this experiment we may conclude with certainty that the 

 principle of action of the respiratory movements does not reside 

 in the cerebral lobes: the destruction of the cerebroid ganglia, 

 by suppressing the intervention of the will, appears only to mo- 

 dify slightly the rhythm of the respiration, which becomes less 

 capricious and more regular. 



