46 



THE COMPOSITION OF EXPIRED AIR, 



b b are the two aspirating flasks, of four litres' cajjatity, partially filled with saturated salt solu- 

 tion. By reversing their positions these aspirators give a continuous current of air. The rubber 

 cork closing the top of these flasks carries two glass tubes with glass stojicocks, and the apparatus 

 is so constructed as to maintain the air current in the same direction by closing one. and opening 

 the other, of these glass stopcocks when the flasks are reversed in their positions. 



The Pettenkofer tubes containing the Ba(HO)„ are attached to the stative c, and those con- 

 taining the [)yrogallate solution to the stative d. 



e represents a stopcock in the tubing connecting the aspirators. This serves to control or 

 arrest the aspiration. 



i 



Fig. 7. — Modified Haitiniond Apparatus (devised by Abbott). 



The results obtained with this modification of the apparatus are shown in Table H. The same 

 animal was used in each of the si.x different experiments performed, and it failed to succumb to the 

 conditions present in any of them. In the later experiments, in which the aniinal was placed in a 

 one-litre bell-jar, it failed to reduce the proportion of O in the volume of air within the apparatus 

 (about six litres) to such an extent as 10 endanger its life, even with the additional reduction of O 

 taking place in the two Pettenkofer lubes containing Buchner's solution of alkaline pyrogallate. 

 The percentage of CO, remained quite low through the absorption by the Ba(HO)5 in the five 

 Pettenkofer tubes. The construction of the apparatus permitted the continuous circulation of the 

 air within the apparatus so that the animal was constantly breathing air that had been breathed and 



Table H. 

 MDniFii-.D "ii.^mmond" experiment. 



