roller: respiratory responses in grasshoppers. 221 



to a minimum under the high pressure. Moreover, this pres- 

 sure was not as injurious to the tissue as a pressure of 280 

 pounds, under which they did not live more than two days, 

 probably because that pressure produced inflammatory con- 

 ditions in the viscera and tissue corresponding to that of the 

 lungs of higher animals. 



It would seem, therefore, that sudden high pressure acting 

 for a few minutes or a few hours, depending upon the maturity 

 of the animals, the time of the year, and the condition of the 

 grasshopper, whether moribund or not, acts as a toxic sub- 

 stance, somewhat like strychnine, directly upon the nervous 

 system, producing convulsions that are of long duration. 

 Moreover, when the pressure acts for one or several days, the 

 tissue of the normal insect is so affected that if it has not died 

 from the changed condition it has severe convulsions when it 

 is removed from the pressure. The spasmodic tetanic move- 

 ments of the appendages may appear within a few minutes 

 and often after half an hour's exposure to atmospheric pres- 

 sure and last for several hours. They may entirely recover 

 from the spasms, or the respiratory movements may have 

 ceased when the animals are taken from the pressure machine 

 and some time later again reappear in air. If that is the case 

 the convulsive movements may usher in respiratory activity. 



