222 JOSEPHINE ALBERTA WILLIS. 



although sufficient data have not as yet been collected to state 

 this exactly. 



It would be of some importance to know the proportion of 

 carbon dioxide that exists in the blood as free carbonic acid since 

 the hydrogen ion concentration of the blood would be affected by 

 varying carbon dioxide tensions unless a strong buffer system 

 were present. With this idea in mind, a colorimetric hydrogen 

 ion concentration determination on the same principle as that 

 described by Cullen (10) was made and seems to indicate that the 

 normal blood of Melanoplus differcntialis is near a pH of 6.1. 



SUMMARY. 



1. It appears that exposures of Melanoplus differ en lialis and 

 Melanoplus femur rubrum to a stream of pure carbon dioxide for 

 various lengths of time up to about 30 to 40 minutes produce 

 reversible effects. Further, the time to the first movement and 

 to recovery after short exposure seems to be independent of the 

 length of exposure. Longer exposures to the gas require longer 

 periods for recovery. 



It follows that the rate of the first movement and of recovery 

 per minute exposure to the gas, up to 30 to 40 minute exposures, 

 decreases rapidly. Above this limit the decrease in rates is 

 imperceptibly gradual or remains constant until the exposure is 

 sufficiently long to kill. 



2. At 5 to 24 hours exposure to pure carbon dioxide, the 

 animals are irreversibly affected and finally die. They may or 

 may not exhibit reflexes upon removal from the gas. 



3. Characteristic behavior, due to the influence of carbon 

 dioxide, is exhibited. 



4. There are three interdependent factors influencing the 

 exchange of gases between the animal and the air in an enclosed 

 space, namely, the original per cent, of carbon dioxide; the 

 original per cent, of oxygen; the original ratio of carbon dioxide 

 to oxygen. 



LITERATURE CITED. 



1. Bodine, J. H. 



'22 Jour. Exp. Zool., XXXV., 47. 



2. Walling, Eulalia V. 



'06 Jour. Exp. Zool., III., 621. 



