Action of Carbonic Acid 923 



hour, whereas the heart of the former stops in 2 or 3 minutes. But 

 these conditions are quite different from those of my present ex- 

 periments. Here we are dealing with carbonic acid slowly formed 

 by the organism itself, and not with a flood of acid reaching the 

 blood of the left heart suddenly. 



There is one last point left to study. When the animal is 

 brought back to free air, even though its blood and its tissues are 

 laden with an enormous proportion of carbonic acid, it recovers. 

 And so the dogs in Experiments DCVI, DCXII, DCXIII, survived, 

 although their arterial blood contained 73.3, 82.8, and 87.2 volumes 

 of C0 2 , and the body temperature had dropped to 25° (Exp. 

 DCXII) . 



They recover gradually; their respiration accelerates, as does 

 the heart; their temperature rises, and strength returns with sen- 

 sitivity, which reappears in 10 or 15 minutes. 



But very strange nervous symptoms always appear at this time; 

 these are rigors with a few clonic convulsions, or slow and languid 

 movements, like those of a hibernating animal which is warmed 

 and which is awakening. That lasts a few minutes, during the 

 phase in which insensibility still persists. 



One might think that these phenomena are due in part to the 

 considerable loss in temperature of the experimental animals. That 

 is not the case, for in Experiments DCXVI and DCXIX, in which 

 insensibility was obtained early by respiration of supercarbonated 

 air, and in which there was no loss of temperature, the same symp- 

 toms appeared. 



They are therefore related to the elimination of excess carbonic 

 acid; the return to its normal state of the anesthetized spinal cord 

 is shown by disconnected stimuli which for some minutes cause 

 convulsive symptoms. 



We know that, according to M. Brown-Sequard, carbonic acid 

 is a poison which causes convulsions; the violent symptoms which 

 mark the end of asphyxias and quick hemorrhages are explained, 

 according to him, by the action of the carbonic acid accumulation in 

 the tissues. Long ago I replied to this theory, which, I hope will 

 not return for discussion today. But here, by a singular coincidence, 

 these convulsions, which the carbonic acid was accused of pro- 

 ducing, are absolutely the sign of its elimination. 



I do not think that these convulsive symptoms of the return to 

 sensibility constitute a serious obstacle to the use of carbonic acid 

 by surgeons. They are surely much less terrifying than the violent 

 struggles which so often mark the beginning of the action of chloro- 



