920 Experiments 



the experiment, as in Figure 76, but the quantity of carbonic acid 

 contained in the blood (Fig. 77), we see that this decrease in the 

 number of heartbeats follows quite regularly the increase in the 

 carbonic acid of the blood. 



The detailed account of the different experiments shows that 

 the heartbeats persist after the respiratory movements have ceased; 

 in Experiment DCVI, the heart continued to beat for about ten 

 minutes. 



On the other hand, we see that the blood pressure in the arteries 

 is modified only very slowly by the accumulation of carbonic acid 

 in the blood and the tissues. At the very beginning it seems in- 

 creased a little (Exp. DCXV and DCXVI) ; but it is still from 12 to 

 14 cm. at a time when there is more than 90 volumes of carbonic 

 acid in the blood (Exp. DCXIV) , and from 11 to 15 when there is 

 95 (Exp. DCXV), and even from 8 to 10 when there, are only 8 

 respirations to the minute, when the temperature has fallen to 28°, 

 and when the arterial blood contains more than its own volume of 

 carbonic acid (Exp. DCXV) . 



Fig. 78 — Death by carbonic acid; last respiratory movements. (Exp. DCXV.) 



So, in progressive poisoning by carbonic acid, the heart is the 

 ultimum moriens (last to die), and its beating is the last sign of 

 life which one can observe in the dying animal. 



The number of respiratory movements decreases equally; at the 

 beginning of the experiment it often increases, but when the car- 

 bonic acid of the blood reaches a proportion above 90 volumes, 

 the slackening assumes considerable intensity. For Experiment 

 DCXV, these phenomena are easy to study in the summarizing 

 table and in the lines R of Figures 76 and 77. In Experiment 

 DCXIV, during the last hour of life, there were only 2 to 4 respira- 

 tions per minute; at the very end, there was only one every two 

 or three minutes, and in Experiment DCVI, one every three or 

 four minutes. At the end, their depth decreased like their number, 



