678 Experiments 



sumption in a given time diminishes when the pressure itself 

 diminishes; this fact is shown very clearly in graph A of Figure 52, 

 which indicates the average of the results of the two preceding 

 experiments. 



The production of carbonic acid gives rise to similar conclu- 

 sions. Graph A' expresses its different stages. 



Let us refer now to the experiments of Chapter I, Subchapter I, 

 and particularly to Table I, which summarizes them. We find here 

 all the elements necessary for our calculation. Now if, without 

 following all the details of the experiments, we take averages at 

 different decompressions, we see that, in one hour, a sparrow: 



Oxygen CO 



At normal pressure (Exp. 1, 2, 3, 4) consumed 147 cc. and produced 122 cc. 

 At about 50 cm. (Exp. 5, 6, 7, 8) consumed 118 cc. and produced 97 cc. 

 At about 30 cm. (Exp. 13, 14, 17) consumed 80 cc. and produced 65 cc. 

 At about 24 cm. (Exp. 24,25,26,27) consumed 72 cc. and produced 57 cc. 

 At about 20 cm. (Exp. 33) consumed 60 cc and produced — — 



These results are indicated by Graphs B and B' in Figure 52. 

 We see that, in spite of the important difference of methods (since 

 here the sparrows remained until death, and consequently towards 

 the end of life were all subjected to the same oxygen tension, the 

 tension which produces death) , the results have remarkable agree- 

 ment with the preceding ones, not only as to the general direction 

 of their variation, but even as to the proportion of this variation. 



I am therefore quite justified in drawing from this collection 

 of data the conclusion that, at low barometric pressures, an animal 

 consumes, in a given time, a considerably smaller quantity of oxy- 

 gen, and produces a considerably smaller quantity of carbonic acid 

 than at normal pressure. This diminution, which increases propor- 

 tionately as the pressure is lowered, is clearly apparent at a diminu- 

 tion of a third of an atmosphere, which corresponds to a height 

 of more than 3000 meters above sea level. 



We shall refer frequently to the consequences of this important 

 principle, which is sufficient explanation, evidently, of all the symp- 

 toms caused by lowered pressure. 



2. Urinary excretion. After having ascertained that oxygen 

 consumption and the intra-organic combustions which result in a 

 production of carbonic acid are considerably diminished by a stay 

 in decompressed air, I had to investigate whether these modifica- 

 tions of nutrition do not also appear in the urinary excretion. 



I have given particular attention to urea. The analyses were 

 made sometimes by the method of M. Grehant (use of the Milon 



