858 Experiments 



persist, either at the time of the sudden reestablishment of normal 

 pressure some vesicle must be broken, thus allowing the air to 

 penetrate the pleura; or after a long stay in the vacuum, gas or 

 liquids must be emitted, and it is probably for this reason that, 

 according to Veratti, the lungs are found in this state only when 

 the animals have remained some time under the pneumatic bell. 



As to the escape of gas into the blood, to which former authors, 

 since Robert Boyle, have attributed such an important part, and 

 which F. Hoppe considered the principal cause of death, I must 

 say that I have found no free gases in the blood vessels when the 

 decompression was sudden any more than when it was more care- 

 fully controlled. And yet in vitro the liberation of the gases of the 

 blood begins under low decompression. For instance: 



Experiment DIV. June 23. Two glass tubes are filled, one with 

 blood, defibrinated and settled, the other with water. Two hours 

 after, no gas bubble having escaped, we begin to lower the pressure, 

 stopping for 5 minutes every 10 centimeters. 



At a pressure of 66 cm., no bubbles of gas escape; at 56 cm., noth- 

 ing; at 46 cm., bubbles appear on the walls of the tubes, both in the 

 water and in the blood; at 36 cm., the escape is abundant in both tubes. 



An escape of gas must therefore take place in the blood vessels, 

 and first in the venous system where the pressure is less. But we 

 must note that the oxygen, granting that it leaves the blood, must 

 be immediately absorbed by the tissues, which are eager for it; 

 that the carbonic acid must pass through the pulmonary membranes 

 with the greatest ease; and that the escape is limited to the nitro- 

 gen, the proportion of which (from 1 to 2 per 100 volumes of blood) 

 is so slight. And, as the escape is very slow, it no doubt has time 

 to diffuse by way of the lungs. So that whether blood is drawn 

 from the living animal, as we succeeded in doing at a pressure of 17 

 centimeters (Experiment CLXXIX) or the blood of an animal 

 killed by sudden or slow decompression is examined, no free gases 

 are found in it. (See particularly Experiments DI, DII, and Dili, 

 in which search for gases was made with the greatest care.) 



