220 KANSAS UNIVERSITY SCIENCE BULLETIN. 



high atmospheric pressure on the respiration in grasshoppers 

 strengthens those obtained by Smith on mammals and birds. 

 He showed that convulsions occurred in birds in three minutes 

 if exposed to oxygen of 280 per cent, of atmospheric pressure 

 or fourteen atmospheres, and in mice in twelve minutes, 

 under an oxygen tension of 400 per cent, atmospheric pres- 

 sure or twenty atmospheres. 



Smith's final experiments led him to conclude that the con- 

 vulsions were the result of high tension. For testing this 

 question, deviscerated grasshoppers proved ideal material, 

 since most of the trachea and blood were removed, leaving 

 the active respiratory muscles and their centers directly ex- 

 posed to the pressure. 



It was seen from the foregoing experiments that the devis- 

 cerated grasshoppers displayed slight convulsions when re- 

 moved to ordinary atmospheric pressure, often they had been 

 subjected suddenly to a pressure of 280 pounds, or fourteen 

 atmospheres. Moreover, that tetanic convulsions that lasted 

 for several hours appeared if they were kept under that high 

 pressure one hour. Under the same conditions, the normal 

 animals, which had exaggerated respiratory movements when 

 first subjected to the pressure, and later very faint ones, when 

 exposed to ordinary air, gradually increased the sluggish re- 

 spiratory movements to exaggerated ones, that later became 

 quite normal again. Furthermore, it was shown that the 

 normal and deviscerated both displayed convulsions if kept 

 under this high pressure twelve hours, though they were very 

 gradually removed from high to ordinary pressure. They 

 ceased all respiratory activity that could not be revived if 

 kept under 280 pounds pressure for two days. Moreover, if 

 the pressure was gradually raised to 280 pounds, or fourteen 

 atmospheres, convulsions failed to appear either in the devis- 

 cerated or normal grasshoppers kept under these tensions as 

 long as three days, or until thoy died. 



It was interesting to learn that the grasshoppers lived longer 

 — in fact, much longer — than in ordinary air pressure, with- 

 out food. When high tensions of 200 pounds or ten atmos- 

 pheres alternated with that of ordinary air, they were in a 

 more or less comatose condition and metabolism was reduced 



