Nervous System on the Respiration of Insects. 281 
nervous system, and that this region in the Dytici corresponded 
with the metathoracic centre or ganglion, the function of which 
would be to excite the respiratory movements and to coordinate 
and maintain them. On the other hand, he supposed the move- 
ments of the posterior part of the abdomen connected with 
respiration to be under the influence of the subcesophageal 
ganglion. 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 
complete 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 Dydicus experimentation is diffi- 
eult, 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. 
