746 Experiments 



formed, while at a tension corresponding to 18 atmospheres of air 

 the consumption was only 0.7 and the production 0.5. 



These experiments show very clearly that the absorption of 

 oxygen and the production of carbonic acid decrease when the 

 oxygen tension increases; the difference increases in proportion to 

 the length of the experiment. Experiment CCCVI shows that at 9 

 or 10 atmospheres of air this effect is produced clearly, and that at 

 this low pressure death may occur after an exposure that has been 

 prolonged enough. 



The second experimental method I used consisted of collecting 

 and measuring all the carbonic acid produced by an animal during 

 a certain time under different pressures but in a current of air that 

 is always pure. 



Experiment CCCVI. Rat weighing 160 gm. 



July 28. Placed for a half hour in the Seltzer water apparatus, 

 at normal pressure, under a current of air providing 2 liters per min- 

 ute. The apparatus is immersed in water at 20°. The air which escapes 

 is collected in a bag, and then connected with the potash bubbler of 

 Figure 65, which absorbs all the carbonic acid from it; the carbonic 

 acid is then extracted by one stroke in the mercury pump. 



The temperature of the animal dropped from 38° to 37.5°. 



It produced 247 cc. of carbonic acid. 



August 2. Same animal, same general arrangements. 



Kept under a current of air but this time at a pressure of 9 

 atmospheres, during the same length of time. 



On being taken from the apparatus, its temperature has dropped 

 from 38.1° to 34.6°. 



Produced 176 cc. of carbonic acid. 



In two of the experiments (CCXCIII and CCXCIV) made on 

 dogs, which were reported in the preceding subchapter, I measured 

 the oxygen consumption, and at the same time the production of 

 carbonic acid, not during the compression, but during the moments 

 following the decompression, and even in the midst of an attack of 

 convulsions. 



This measurement was interesting only from the comparative 

 point of view. The method which I used, which makes no claim to 

 absolute accuracy, allows me to compare what a dog was capable of 

 absorbing and producing before being subjected to compressed air 

 with what he consumes and produces when he has been taken from 

 the cylinder. 



The experimental animals had a tube in the trachea. I con- 

 nected this tube with a bag filled with a known volume of air and 

 let the animal breathe into the bag for a certain time. Since the 



