282 M. E. Baudelot on the Respiration of Insects. 



^ In a second experiment, at 2 o'clock p.m., I made a ligature a 

 little behind the metathorax, and effected the section of the body 

 immediately in front of this. In this way I was quite sure that 

 I had removed the metathoracic ganglion, which is situated at 

 the centre of the space between the insertions of the second and 

 third pairs of legs. At 4 o'clock, however, the number of re- 

 spirations was eighteen per minute, and the respiration only pre- 

 sented a few irregularities ; at 3 o'clock p.m. next day it was still 

 possible to perceive some respiratory movements. To leave no 

 chance of uncertainty, I dissected the portion of the body which 

 I had cut away in front of the ligature : it contained the three 

 thoracic ganglia as well as the tirst abdominal one. 



In a third experiment, the ligature and section were made at 

 the fifth segment of the abdomen, when the respiratory move- 

 ments, although much weakened and rendered irregular, still 

 persisted for more than twenty-four hours. Nevertheless the 

 portion of the body anterior to the section contained the whole 

 of that part of the nervous chain that extends from the head to 

 the fifth abdominal ganglion. 



From these two latter experiments it is quite evident that the 

 metathoracic ganglion is not the prime motory focus of the 

 respiratory movements, since, after the complete removal of this 

 ganglion, respiration continued to be effected for a period of 

 twenty-four hours. With regard to the suboesophageal ganglion, 

 I have been unable to discover in it any special coordinative 

 property ; and when the respiratory movements were produced 

 independently of its influence, I always saw the five appendages 

 of the last abdominal segment concurring normally, as before, 

 in the respiratory act with the whole of the other segments of 

 the abdomen. 



I repeated these experiments upon the adult Libellula with 

 equally conclusive results. The complete section of the body 

 behind the metathoracic ganglion does not cause the suspension 

 of the respiratory movements in the portion posterior to the 

 section, any more than in the larva. Thus in one case, in which 

 I made a ligature and then a section behind the second segment 

 of the abdomen, the respiratory movements persisted for eight 

 hours ; the inhalations, which were very regular, rose to fifty 

 per minute, and yet the metathoracic ganglion had been cut 

 away with the anterior portion. In another experiment, the 

 respiration lasted seven hours; it was very regular, and the 

 number of inhalations was sixty-five per minute. 



Lastly, in a final experiment, I cut a piece out of the abdomen 

 including only three segments (4-6) ; and in this I observed 

 very appreciable movements of respiration for some time. 



These results and others of precisely similar nature, which I 



