Gases of the Blood 609 



contained in the arterial blood could, at pressures of 30 or 40 cm, 

 drop to 9 cc. per 100 cc. of blood; that is, at these pressures the 

 arterial blood contained considerably less oxygen than ordinary 

 venous blood. 



The diminution of the carbonic acid was likewise (Col. 9) very 

 considerable; the figures expressing the proportion of this gas have, 

 in fact, dropped almost to 20 cc. per 100 cc. of blood. We shall 

 refer later to the conclusions derived from these data. 



In comparing the experiments made at the same degree of de- 

 compression, we find that the decreases in oxygen and in carbonic 

 acid have varied peculiarly. The lowest figures of Columns 8 and 

 9 are not at the end, but towards the middle of the table. The re- 

 sults of this fact are still more evident in Columns 14 and 15; there, 

 for example, at a pressure of 36 cm., that is, about a half atmos- 

 phere, the arterial blood has lost, in the different experiments, 

 from 36.1 to 55.6 per cent of its oxygen, and from 16.8 to 38.6 of 

 its carbonic acid. 



It is difficult to explain these differences by the different be- 

 havior of the animals observed while the pressure was being 

 lowered. This element may be important; but it cannot be the only 

 one, and very probably animals with the same behavior may differ 

 in the result for the same decompression, some losing more and 

 others less oxygen or carbonic acid. This has interesting practical 

 results which I shall stress in their place. 



Laying aside these individual differences, still more difficult to 

 study here than in the case of normal pressure, and blending them 

 in averages, we see (Col. 14) that on the average, the arterial blood 

 at a pressure of 56 cm. contains 13.6 per cent less oxygen than at 

 normal pressure; that at 46 cm., it contains 21.1 per cent less; at 

 36 cm., 43 per cent, and at 26 cm., 50.7 per cent. So at 26 cm., on 

 the average, half of the oxygen of the blood has disappeared. 

 These figures show that the diminution of this gas is far from fol- 

 lowing Dalton's Law, which would give, for the same decompres- 

 sions, losses of 26.3; 39.4; 52.6; 65.8 per cent. 



• The losses of carbonic acid (Col. 15) for the same decompres- 

 sions, on the average, are 10.9; 14.0; 29.2; 38.2 per cent of the gas 

 existing at normal pressure; that is evidently still farther from 

 Dalton's Law. 



These figures even show that the average loss of carbonic acid 

 is less than that of oxygen. The greatest proportion of loss, for the 

 former gas (Col. 15) was 41.8 per cent; for the second, we twice 

 had (Col. 14) 55.6. In one case, (Exp. CLXXII), at a pressure of 



