910 Experiments 



87.2 (Experiment DCVI) , and 93.8 (Experiment DCX) ; yet, in the 

 last case the animal died during the night. 



And therefore, as one might have thought a priori, it is not so 

 much the tension of the carbonic acid in the outer air as its tension 

 in the blood that causes death. And besides, the first acts only in 

 causing the second. 



This explains why animals which at the very outset were made 

 to breathe a superoxygenated air containing 40% of carbonic acid 

 (Experiments DCXVI and DCXIX) , or even 52.8% (Experiment 

 DCXVIII), did not die immediately. They had to have time to 

 store up in their arterial blood a sufficient quantity of C0 2 , and 

 this process was carried out in two different ways: 1) by hindering 

 the escape of the carbonic acid of the venous blood as it passed 

 through the lungs; 2) by absorbing the excess carbonic acid con- 

 tained in the inspired air; this absorption, moreover, is proved by 

 Experiment DCXVIII, in which the respirable mixture, after 11 

 minutes of the experiment, contained less carbonic acid than be- 

 fore, and more oxygen. 



3. The Accumulation of Carbonic Acid in the Tissues. 



But the question is still more complex. It is not only in the 

 blood that the carbonic acid must be stored up progressively, the 

 tension of which in the respired air hinders its regular excretion. 

 The carbonic acid of the blood comes from the tissues; in the nor- 

 mal state, a certain equilibrium of tension is established between 

 the proportion of this gas which remains in these tissues, and that 

 which remains in the blood, after the elimination due to a regular 

 respiration. If some cause maintains an excess of carbonic acid in 

 the blood, an excess of it must remain in the tissues. The whole 

 organism then must be completely impregnated with this gas, 

 which is highly soluble. 



To inform myself about this delicate point, I resorted to the fol- 

 lowing experimental procedure. A determined weight of the tis- 

 sues of the experimental animal, which had been cut into small 

 pieces, was placed in a measured flask, of about triple capacity. 

 The flask was then quite filled with a rather strong solution of 

 potash or caustic soda; a similar solution was kept as control in 

 another flask quite full and well corked; I let the whole thing stand 

 for twenty-four hours, shaking it quite often, and I considered 

 that in this length of time, the alkali had taken up all the carbonic 

 acid which the tissues might contain. 



I then took a certain quantity of the liquid, and introduced it 



