Sudden Changes in Pressure 887 



swellings, the swelling of the breasts, etc., of which we have given 

 several examples in the chapter devoted to history. 



In summary, sudden decompression causes many more or less 

 severe symptoms, all of which are easily explained by the libera- 

 tion in the blood plasma as well as in the interior of the tissues, 

 of the nitrogen which was dissolved in excess under the influence 

 of the pressure. 



I admit that, in this collection of data which, although infinite 

 in variety, still has a single simple cause, one point still surprises 

 me. I cannot understand why, m certain dogs subjected to high 

 pressure, the blood extracted from the vessels did not contain free 

 gases: for instance, in Experiments DXLVI and DLVI, in which 

 the pressure was 6V2 and 8 atmospheres. Experiment DLXIII is 

 particularly interesting in this connection: the dog, decompressed 

 after a long stay at 6 atmospheres, was paralyzed, and yet no free 

 gas appeared in its blood; but the symptoms having grown more 

 serious, gas was found after death not only in the blood but also 

 in various organs, and particularly in the spinal cord: this was 

 probably the cause of the immediate paralysis. 



It was also somewhat difficult at first to understand why dogs 

 suddenly decompressed from 5 or 6 atmospheres, rabbits from 6, 

 7, 8, and sparrows from 8, 9, 10, did not die, and did not even show 

 any symptoms, though they certainly had free gases in the blood, 

 since I sometimes observed the presence of gas in an experimental 

 animal, as in Experiments DXXXIX and DLXIV. I think that this 

 apparent anomaly should be explained by the fact that the escape 

 of bubbles which were very small at the time permitted them to 

 pass without hindrance through the system of capillaries and to 

 gather in the venous system. Now if all the gas thus set free is 

 collected in the veins, it cannot constitute a serious danger for the 

 animal. 



Let us consider again a calculation which we have already made. 

 At 5 atmospheres, for example. Table XII shows that a dog has an 

 average of 6 volumes of nitrogen per 100 volumes of blood, that is, 

 about 4 volumes more than the blood can dissolve at normal pres- 

 sure. Let us take a dog weighing 10 kilos, and let us suppose that 

 it has in its blood and lymph vessels 1 liter of liquid; there will 

 be 40 cc. of nitrogen, with about 10 cc. of C0 2 which, as a maximum, 

 will collect in the hollows of the right heart. This collection will be 

 made progressively, for it is well known that in a liquid super- 

 saturated with gases by pressure, the gases will not escape instan- 

 taneously at the time of the decompression. 



