694 Experiments 



Subchapter III. 



MEANS OF AVERTING THE SYMPTOMS OF 

 DECOMPRESSION 



The numerous data now enumerated have shown very clearly 

 that the symptoms of decompression are due, not to the lessening 

 of atmospheric pressure, but to the diminution of the tension of 

 the oxygen, which no longer enters the blood, or consequently the 

 tissues, in sufficient quantity to maintain the vital combustions at 

 their normal rate. The preventive measures for these symptoms 

 are naturally derived from this very idea. 



The tension of a gas, we have often said already, is expressed 

 by the product P x Q, in which the barometric pressure P is multi- 

 plied by the percentage of Q of the gas in the surrounding mixture. 

 If then we increase the factor Q at the same time that we diminish 

 factor P by the use of the pneumatic pump, there will be no 

 change in the tension, and the symptoms should be averted. At 

 the same time, if the result justifies our expectations, the theory 

 which serves as the base will once more be verified. 



But the experiment, under the form I have just indicated, is 

 very hard to carry out. We reach the same conclusions by ex- 

 ecuting it in the conditions of the experiment whose details I 

 shall now give. 



Experiment CCLI. April 23. Sparrow, under a bell of 1.5 liters, 

 on the plate of the pneumatic machine. Outside pressure is 75 cm. 



3:20, brought in a few minutes to 25 cm. pressure; respiratory 

 rate 212. 



At 21 cm., whirls, falls head over heels, about to die. I restore 

 normal pressure by admitting air very rich in oxygen (by accident, 

 outer air enters at the same time) ; the bird recovers immediately and 

 seems lively and well. 



3:30, the air then contains 35 per cent of oxygen. I bring the 

 bird to 18 cm. pressure; he is then very sick, with a respiratory rate 

 of 176; I admit oxygen again, he recovers immediately. 



3:40, the air contains 77.2 per cent of oxygen. The bird under 

 13 cm. pressure has a respiratory rate of 168, but he falls only at 

 10 cm. Likewise recovers immediately after the admission of super- 

 oxygenated air. 



3:50, the air contains 87.2 per cent of oxygen. The sparrow, at 

 10 cm., has a respiratory rate of 176, and seems in no danger; but 

 at 8 cm., he falls on his back and is about to die. New admission of 

 oxygen, recovers again. 



4:05, the air contains 91.8 per cent of oxygen. We continue to the 



