EXPERIMENT STATION BULLETINS. 577 



as the hydrogen filled "C." "A" was connected with a heavy rubber 

 displacement-bag which served to protect the pyrogallate from the air. 

 As soon as "C" was sufficiently filled with gas and the two-way cock 

 was closed, gas pressure forced the sulphuric acid down to the position 

 shown and the gas-generation ceased. The two glass bulbs forming the 

 left hand portion of the pipette contained mercury. 



Nitrogen could be obtained with this apparatus by simply drawing 

 air into "C" and then waiting a few minutes until the alkaline pyro- 

 gallate had absorbed all oxygen and carbon dioxide from the confined 

 air. 



Experiments were carried out in so nearly the same way with the 

 two gases and the results were so comparatively uniform that the record 

 of a single experiment with nitrogen will be sufficient. 



The following experiment was carried out at a temperature of 21° 

 to 22° C. Enough air was drawn into container "C" (Fig. 5) to leave 

 about 200 c. c. of nitrogen. Two specimens of P. coi-nutus (3.46 grams.) 

 were placed in a respiration container and the mercur}^ raised to near 

 the top of this container. It was then at once connected through a 

 capillary tube with the thimble "th" of "C." Nearly all the nitrogen 

 was drawn into the respiration container with the small amount of 

 air that had been left with the beetles. A moment was allowed for 

 this air and nitrogen to mix, after which almost all the mixture was 

 transferred to "C." Transfers were made back and forth, in this way, 

 during a period of 45 minutes so that all the oxygen was taken up by the 

 ' pyrogallate — the tracheae of the insect had time to become filled with 

 nitrogen. At the end of that time the gas with the insects was tested 

 and found free from oxygen and carbon dioxide. A mark had been made 

 on the respiration container so that between 80 and 85 cubic centi- 

 meters of nitrogen could be retained in it. This container was quickly 

 moved to the measuring burette (Fig. 4), in wh'ich nitrogen had just 

 been measured during the test mentioned above. The mercury was 

 raised until it poured from the transfer connection-tube of the burette 

 into the thimble of the respiration container, and thus connection was 

 made under mercury seal. All the nitrogen with the beetles was trans- 

 ferred at once to the burette and measured — found 82.85 c. c. of nitrogen. 

 The gas was all immediately transferred back with the beetles and con- 

 nections left standing until the experiment was ended — time 10% 

 hours. 



Gas measured at end, 83.30 c. c. 



83.28 c. c. after phosphorus pipette. 



82.85 c. c. after KOH pipette. (Nitrogen). 



0.45 c.c. of CO, 



The hearts were beating within one-half hour after these beetles were 

 removed to fresh air and both beetles recovered. 



It will thus be seen that the amount of nitrogen at the end was the 

 same as at the beginning of the 10% hour period. The volume of the 

 gas with the beetles had increased 0.45 c. c. during the confinement — 

 the increase being due to carbon dioxide which the beetles were able 

 to excrete even in the absence of any free oxygen. There were no white 

 fumes in the phosphorus pipette at all, showing that no oxygen was 

 73 



