EWING : OBSERVATIONS ON ACRIDID^. 317 



normal manner after about half an hour following the opera- 

 tion, or until all shock effects have worn off. By the removal 

 of the successive abdominal ganglia of the ventral chain like 

 results were obtained, but in addition to these there is a loss of 

 motion in the ovipositor when the last abdominal ganglion 

 was removed. 



By severing the longitudinal commissures between different 

 ganglia of the abdominal ventral nerve-cord, or by severing the 

 abdomen from the thorax and cutting it transversely into two 

 or more parts, it is found that the different parts into which the 

 abdomen is divided continue to execute rhythmical respiratory 

 movements, provided the removed piece contains at least three 

 segments. This is in accord with the results obtained by Miss 

 Hyde** in Limulus. 



The respiratory and spiracle movements in the abdomen may 

 stop for a shorter or longer period of time after the abdomen is 

 cut from the thorax, and then spontaneously begin their move- 

 ments again, or they may continue uninterruptedly but with 

 less frequency and with less force. Moreover, if two drops of 

 a half per cent, curare are injected into the abdomen of a large 

 grasshopper, all voluntary muscles and respiratory movements 

 and spiracles seem paralyzed for from two to six hours. The 

 spiracles are closed, and the abdomen is relaxed in the expira- 

 tory phase. This proves that inspiration is due to an active 

 contraction of certain voluntary abdominal muscles. 



If a transverse section is made between the third and fourth 

 abdominal segments a small pulsating organ is seen. It is situ- 

 ated close to the ventral side of the body below the alimentary 

 canal and almost directly opposite the heart. I have been un- 

 able to determine from literature what it is. 



VII. Conclusion. 

 1. Neither the supraoesophageal ganglia or brain of the grass- 

 hopper nor the suboesophageal ganglion, which has been 

 regarded by some authors as analogous to the medulla of verte- 

 brates, is the centre for respiratory movements. Furthermore, 

 the meso-thoracic and meta-thoracic ganglia, which, according 

 to Faivre, presides over the respiration in the water-beetle, 

 Dytiscus, do not control the mechanism of the respiratory raove- 



». Hyde, I. H., Journal of Morphology, 1897, vol. 9, No. 3, p. 431. 



