612 Experiments 



the blood and the air, the circulatory movements, the probable 

 formation during the absorption of oxygen of substances capable 

 of acting on the elimination of the carbonic acid, the increased 

 temperature of the living body, are conditions which existed in 

 one case and not in the other. Without mentioning the still en- 

 tirely unknown elements of the complex problem of respiration, 

 we have enough to give us an understanding rather than an ex- 

 planation of the differences in our results. 



Furthermore, I wished myself to make experiments in vitro, 

 in which I should make changes in pressure much greater than 

 those obtained by M. Fernet. The report of these experiments will 

 form subchapter V of the present chapter. 



The reader may have noticed that I studied the composition of 

 the blood gases beginning with 56 cm. Between 56 cm. and 76 cm.. 

 I thought I should not take account of any of my experiments. 

 Here the value of the modifications found is precisely of the order 

 of the errors of analysis. To draw any conclusions, one would have 

 to make a considerable number of experiments and draw an aver- 

 age which would express the direction if not the real value of 

 the modification. Now this direction seems to me sufficiently de- 

 termined by what we know already. The decrease of the oxygen 

 and the carbonic acid of the blood, evident and constant at 56 cm., 

 although very variable as to its value, surely begins considerably 

 sooner, but at barometric levels and with an intensity which must 

 vary from one animal to another, or in the same animal under 

 different circumstances. 



On the other hand, all the experiments show that the oxygen 

 is always given off in greater proportion than the carbonic acid. 

 That should be enough to make us think that this rule extends to 

 the period included in the first 20 centimeters of lowered pressure, 

 a period which has this special importance of being the one to 

 whose influence the majority of dwellers in high places are sub- 

 jected. 



If our table of experiments shows that we did not begin at the 

 outset of the decompression, it also shows that we did not go to the 

 end, that is, until the diminution of pressure becomes incompatible 

 with animal life. That was because my apparatuses did not permit 

 me to do so, since leaks which could not be avoided in such huge 

 receivers stopped the decrease of pressure at 17 cm., as I have said. 



I tried to fill this gap by an indirect means. I put a dog under 

 the large glass bell- jar, and let it die there from decreased pressure. 



