882 Experiments 



Chapter IV to which I alluded a moment ago; here no symptom 

 appeared, no gas bubble was freed in the vessels, because the air 

 which the animals were breathing had a very low nitrogen content. 

 But there is better proof; I could, as Experiments DXXVIII, 

 DLVIII, DLXIX, and DLXX show, extract the gases collected in 

 quantity in the heart and analyze them. I did indeed find them 

 composed chiefly of nitrogen; but I must confess that I was much 

 surprised to find, besides the nitrogen, a quantity of carbonic acid 

 which varied from 15% to 20% and even, in one case (Exp. DLVIII) , 

 a little oxygen. 



The explanation of these facts should probably be drawn from 

 the circumstances that the liberation of the nitrogen takes place in 

 little bubbles, which the circulatory movements stir up before they 

 can collect in the heart in vast collections of gas, so that the blood 

 is, as it were, traversed by a current of nitrogen. Now we have 

 known for a long time that such a current carries with it much 

 carbonic acid. 



As for Experiment DLVIII in which I found 2% of oxygen, that 

 is the one in which the apparatus exploded, and in which the ani- 

 mal, which was killed instantly, had not consumed the slight excess 

 of oxygen which had been liberated in its blood. 



At any rate, most of the free gas is made up of nitrogen, and 

 from this fact a very serious danger results; for carbonic acid and 

 even oxygen might be redissolved rapidly, and Nysten - long ago 

 demonstrated that their presence in the venous system is not dan- 

 gerous, unless enormous quantities, especially of carbonic acid, are 

 introduced. It is true that in our experiments there is gas in the 

 arterial system itself. 



It is probable that all the excess nitrogen thus passes to the 

 gaseous state. Now we have seen that at 10 atmospheres there are 

 about 8 cubic centimeters of nitrogen in excess in 100 cubic centi- 

 meters of blood. Supposing that a dog weighing 14 kilograms con- 

 tains 1 kilogram of blood, we find that there may be liberated in 

 the arterial and venous vessels 80 cubic centimeters of nitrogen, 

 bringing with them about 20 cubic centimeters of carbonic acid; 

 that is sufficient to bring on symptoms that are immediately fatal. 

 Now we can picture the effects of sudden decompression. Let 

 us first represent things as bad as possible; let us suppose an animal 

 brought in 2 or 3 minutes from 10 atmospheres to normal pressure. 

 Immediately, in the whole vascular system, gases escape in abun- 

 dance; there is frothy blood in the veins, in the arteries, in the 

 portal system, even in the vessels of the placenta and the foetuses, 



