884 Experiments 



minutes which almost always elapses between the moment of de- 

 compression and that of paralysis, either because the gas does not 

 escape immediately in the whole body, or because a certain time 

 is needed for the bubbles of air to cut off the medullary circulation. 



It is no less strange to see, in certain experiments, for instance 

 DLXXV, life persisting for hours when the almost general paraly- 

 sis of the animal left free only the movements of the diaphragm, 

 and gurgling could be heard in the heart, revealing at the begin- 

 ning the presence of a great quantity of gas in the right heart and 

 the lungs. 



In this case, the animal is slowly asphyxiated, as is proved by 

 the increasing darkness of the blood flowing in its arteries. It is 

 evident that the pulmonary output is insufficient to provide an 

 adequate quantity of oxygenated blood in the arteries. 



If now we ask why the nitrogen thus liberated is not finally 

 redissolved in the blood, or why it does not escape through the 

 lungs, the reply is easy. 



As a matter of fact, the blood circulating through the vessels 

 under normal conditions is almost saturated with nitrogen through 

 the respiration of air; when arterial blood is shaken with air, it can 

 be made to absorb only some tenths of a cubic centimeter of nitro- 

 gen more than it already contained. There is no reason then why 

 the excess which has been liberated should be redissolved. Now 

 the free nitrogen does not escape through the lungs because it is 

 in an atmosphere which is four-fifths nitrogen, and nothing urges 

 it out. 



Continuing this reasoning, we begin to think that there might 

 be an advantage in causing the animal to inhale pure oxygen or a 

 mixture of oxygen and hydrogen, to stimulate at the same time 

 the dissolving of the nitrogen in the blood and its diffusion through 

 the pulmonary membranes. And this I did with some success in 

 the experiments which I shall report later. 



Finally, a third strange fact, the paralysis always began in the 

 hindquarters (except in Experiment DLXII) . Why is this place 

 selected? Is it a sufficient explanation to say: the lumbar region 

 of the spinal cord is the part which works hardest when the ani- 

 mal jumps and runs? I merely remind the reader that paraplegia 

 is also the most frequent symptom in divers and workmen in 

 caissons. 



When death occurs shortly after the beginning of the paralysis, 

 it is evidently under the influence of the same cause as the paralysis; 

 the bubbles of gas, after cutting off the circulation in the lumbar 



