1 I I I < TS OF CARBON DIOXIDE. 215 



vary with the incliviclual. Usually there are slight reflexes, or 

 quivers and tremblings of the legs, the large hind legs often being 

 the first to move. After these reflexes have continued for a few 

 seconds, becoming more and more pronounced, the le- nu- 



cither stiff or limp. This latter condition may be followed 

 shortly by a return of the reflexes and after longer exposure the 

 reflexes may bcinme violent. When the retlexc- 1. 



mimal begins to crawl feebly, slowly re< it> strength and 



api <nual. After shorter exposure the response differs, the 



tir-t m. \i-iiu-iit after removal from the ga- may be a cra\\l <>r a 

 hop, folloued by normal movements. 



Often it is impossible to compare the resistance of the animal 

 \\licn time alone is considered with regard to an arbitrary 

 einl[)oint. However, if the first movement is taken as the re-tilt 

 of a -timulu> brought about by the interchange of A hen a 



ne\\ equilibrium is being established it may be a true endpoim tor 

 comparing resistances to different length expo-iire- to carbon 

 dioxide. As for a comparative resistance of the anim.,U to 

 carbon dioxide taking into consideration the clia; of the 



movements, as numerical data alone do not suffice, it may be 

 said that: (i) MeKinoplus differential/is is nioi. -tant than 

 Mcldni'1'lns femur rnbrum; (2) nymphs of both -p e more 



-tant than adults, they do not succumb idily 



-ver more completely in a shorter length of time. Adult.s 

 undergo tlie most violent reflexes, secrete more >ali\a ami take. 

 the lon-e-t time to recover fully; (3) molting or frc>hly molted 

 animal umb most readily and recover very quickly from 



K \ ii -iMe doses, perhaps due to the softness of the ch.it in ; (4) no 



dilleienccs were observed; (5) star\-ation for t\\ent\ -four 

 hours has no appreciable influence on the recovery from the 

 effects of the ;^as. 



2. A <urc of the Change in Percentage of Carbon Dioxide 



0.\ Due to Respiration or Some Interchange of Gases 



. the Animals and the Air in an Enclosed Spa* 



The following readings are based upon Melanoplus differ entialis t 

 nymphs and adults of both sexes being used. 



A 1 laldane gas anah'sis apparatus was used for determining the 

 per cent, of oxygen and carbon dioxide. The type of container 



