Death in Closed Vessels 577 



marked on that of the x's. I added the results already obtained 

 for pressures lower than one atmosphere. 



We see that the exhaustion of the air reaches its maximum at 

 about 6 atmospheres. At higher pressures, it diminishes rapidly, 

 so that at 24 atmospheres, the bird dies in an air that is almost pure. 



The dangerous action of oxygen is shown very clearly, especially 

 towards 15 atmospheres. 



Line B expresses the results of Columns 7 of Tables V and VII, 

 that is, the proportion of oxygen remaining in compressed air when 

 carbonic acid is allowed to act on the experimental bird. We see 

 that the two curves coincide only at \ x k atmospheres; above that, 

 the acid acts strongly and brings on death in air that is hardly 

 impoverished. 



3. Conclusions. 



The conclusions to be drawn from the data reported in the pres- 

 ent subchapter are more complex than those of the preceding sub- 

 chapter; the intervention of the carbonic acid and of the oxygen, 

 for very high pressures, complicate them. We shall therefore make 

 a distinction: 



1. In confined air, at pressures higher than one atmosphere, if 

 care is taken to eliminate the carbonic acid as it is produced, death 

 occurs in the same conditions as for pressures lower than one at- 

 mosphere, that is, when the oxygen tension drops to a determined 

 value (3.6 on the average for sparrows) . 



This is true only up to about 6 atmospheres; beyond that, the 

 compressed oxygen acts to prevent the exhaustion according to 

 the formula. 



2. When the carbonic acid is not absorbed, it becomes a cause 

 of death at the moment when its tension rises to a certain value 

 (from 25 to 28 for sparrows). 



This is absolutely exact only on condition of using, for rather 

 high tensions, air with low oxygen content, so that the oxygen 

 tension may not rise to the point where it is dangerous to the very 

 life of the birds. 



