Y. Henderson and H. W. Haggard 361 
particularly upon arterial pressure. Jn order to test this point 
therefore we carried out Experiment 5. The point of the ex- 
periment was to administer quite as vigorous artificial respiration 
as in the previous experiments, but with air containing such a 
percentage of CO. as would prevent any reduction in the CO, 
content of the blood. 
For this purpose the apparatus shown in Fig. 1 was used with 
rC 
Fig. 2: 
the addition of that shown in Fig. 2. The latter consisted of a 
glass jar of 12 liters capacity in which a rubber bag (B) was sus- 
pended on the end of a tube (A) which was fastened to the Y 
tube of the apparatus of Fig. 1. Tube C was attached to the 
animal’s trachea. Oxygen was passed into the jar as needed, and 
gas samples were taken, through tube D, while a small escape 
valve (E, at the right of the figure) allowed a little fresh air to 
enter and leave the jar at each reversal of the air current. 
