218 KANSAS UNIVERSITY SCIENCE BULLETIN. 



It was found that, when the grasshoppers were removed to 

 atmospheric pressure after they had been exposed for one 

 hour to a pressure of 250 pounds, the normal were very 

 sluggish and the deviscerated had severe spasms that lasted 

 almost seven hours. The normal and other deviscerated were 

 now placed for twelve hours under a pressure of 250 pounds, 

 and when removed from the pressure the normal insects dis- 

 played spasmodic tetanic movements of the appendages, and 

 the deviscerated had severe spasms. When, during two 

 hours under atmospheric pressure, they had recovered some- 

 what from the tetanic spasmodic state, they were for a third 

 time subjected to 250 pounds pressure. The normal and de- 

 viscerated, when removed from this at the end of six hours, 

 had ceased respiratory and other activity ; but the normal 

 revived in one hour, while the deviscerated in three hours 

 under atmospheric pressure, and displayed spasmodic move- 

 ments of the appendages. Other experiments were pursued 

 with normal and deviscerated mature grasshoppers subjected 

 to a very high pressure for varying periods of time, with the 

 following results : It was ascertained that, when both normal 

 and deviscerated May grasshoppers were removed to atmos- 

 pheric pressure from ten minutes' exposure to 280 pounds 

 pressure, the deviscerated had slight spasms, the normal 

 not. On the other hand, November grasshoppers did not ex- 

 hibit spasms when subjected ten minutes or even three- 

 fourths of an hour to the high pressure of 275 pounds, but 

 they all displayed a sluggish, paralyzed condition at the end 

 of that time. An exposure to the pressure for one hour 

 showed that the animals moved their appendages with diffi- 

 culty, and that after half an hour in atmospheric pressure the 

 deviscerated had spasms, while the intact animals recovered 

 their normal activity. 



Effect of Gradually Lowering the Pressure upon Respiratory Movements 



in the Grasshopper. 



The reduced pressure was obtained by means of a Sprengle 

 pump, to which was joined a glass tube containing the grass- 

 hoppers. As soon as the pressure fell the animals became 

 restless and moved about in the tube. At first a notice- 

 able expansion of the abdomen occurred, due to decreased 



