628 Experiments 



great simplicity, and, in fact, they do so. As it enters into no com- 

 bination, its proportion in the blood depends solely on pressure; so 

 Columns 5, 10, 14 of Table XI show us that it increases considerably. 

 We shall see what is the importance of this considerable quantity 

 of nitrogen when we speak of the effects of sudden decompression. 



And yet, strangely enough, the increase is far from following 

 Dalton's Law. In fact, at 5 atmospheres, for example, we find in 

 Column 5 the average number 6, instead of 11 required by Dalton's 

 Law; at 10 atmospheres, the average number is 10.4 instead of 22. 

 There is therefore about half as much nitrogen as the law would 

 require. That is very striking in the graph Az in Figure 35, in 

 which the straight line shows what the law would require. 



This fact is very instructive, because it shows how incomplete 

 the intrapulmonary agitation is, at least at high pressures. Now 

 the results given by the oxygen tend in the same direction. Ad- 

 mitting that the hemoglobin is saturated chemically with oxygen 

 in the neighborhood of normal pressure, the quantity of oxygen 

 dissolved should be much greater at high pressures than experience 

 indicates. At 10 atmospheres, for example, we should find, not 

 23.4 per cent, but about 29. The insufficient mixing of the air in 

 the lung should be considered here; furthermore, this insufficiency 

 is evident at normal pressure, because blood extracted from the 

 artery always gains considerably in oxygen content from agitation 

 with the air. We shall see that the same thing is true in the case 

 of high pressures. 



All this can be summed up in the following sentence: in the 

 living animal, when the barometric pressure increases, the oxygen 

 increases in the arterial blood, but very slowly; the nitrogen in- 

 creases more quickly, but in a quantity far from that required by 

 Dalton's Law; as for the carbonic acid, it almost always diminishes. 



Subchapter IV 



GASES IN THE BLOOD IN ASPHYXIA COMPARED 

 TO DECREASED PRESSURE 



I think I demonstrated in the first chapter that the symptoms 

 and death in expanded air are the result of weak pressure of out- 

 side oxygen, and that, in a word, it is a matter of simple asphyxia 

 from lack of oxygen. 



If this is so, one should, in the blood of a dog subjected to 



