ANESTHETICS AND CO2 OUTPUT 325 



ture when used as killing agents of grasshoppers and, hence, 

 make them of much cytological as well as of physiological im- 

 portance. Since the movements of grasshoppers normally, 

 when the animals are properly handled, are practically negli- 

 gible, reagents such as anesthetics have little or no inhibiting 

 effects upon body movements. Some chemicals used, how- 

 ever, do inhibit the respiratory movements in a very short time 

 and such an inhibition perhaps diminishes to a slight extent the 

 CO2 output; others, in small doses, do not exert any marked 

 effects upon the respiratory movements. This question is dis- 

 cussed further on when dealing with particular experiments. 



The concentrations of reagents used are not necessarily the 

 same in the case of different chemicals, because some are more 

 soluble in water, more volatile, etc., than others. With any 

 one chemical, however, the concentrations used are such that 

 one may speak of a small or a large dose of the reagent. 



Temperature during any experiment was kept practically con- 

 stant, varying not more than 0.5°C. 



Ether. The amounts of ether used varied from one drop 

 (0.04 cc.) to 1 cc. Amounts of 0.3 cc. to 0.5 cc. and over produce 

 a saturated atmosphere of the chemical in the respiration tube, 

 since a great deal of the reagent is left unvolatilzed in the indi- 

 cator solution. The grasshoppers used comprised all stages of 

 growth, young nymphs to old adults. No marked sex or species 

 differences were noted. 



Briefly outlined, the procedure in any experiment was as 

 follows. A single grasshopper was placed in the respiration 

 tube (25 cc.) containing 5 cc. of indicator solution, and the time 

 required to produce a definite amount of CO2 noted. This was 

 repeated several times and the average used as normal. The 

 reagent was then added to both control and experimental tubes 

 and the time required to produce the same amount of CO2 as 

 in the normal reading again noted. Since the results for dif- 

 ferent individuals are qualitatively alike, the data obtained can 

 be best given by curves showing typical cases. At least six, 

 and in most cases more, experiments were made with every 

 concentration of reagents. 



