Theories and Experiments 483 



occurred very quickly, as happened to three cases, or occurred only 

 after a variable time, as in the other seven cases. 



Then, after accepting this hypothesis, he asks himself what the 

 cause of the spinal hemorrhage can be: 



After due reflection (he answers himself), we are inclined to 

 believe that it is the result of the exaggerated tension of the free 

 gases, in solution in the blood, as a result of the high pressure to 

 which the divers may be subjected. In the diving-suit, as we know, 

 the man is completely isolated from the water by a suit of strong 

 impermeable fabric and a metal helmet fastened upon the collar of 

 the suit. Air is admitted to this covering by means of a pump which 

 communicates with it by means of a flexible tube ending at the back 

 of the helmet. Nothing regulates the quantity or the pressure of the 

 air pumped into the suit. Consequently, the workman often receives 

 too much or too little air; he is compelled to remedy partially the 

 difficulty in breathing which he experiences by being in constant 

 communication with the pumptenders by means of signals consisting 

 of a certain number of tugs given to a signal cord. Nevertheless, by 

 means of this atmosphere which the man keeps around him, he can 

 maintain his respiration and remain whole hours under water. But 

 the greater the depth, and the more prolonged the stay, the more must 

 the blood be laden with an excess of free gases in the state of solu- 

 tion. The lack of regulating mechanism for the pressure must often 

 cause the atmosphere of the suit to be at a pressure greater than is 

 necessary. From the point of view of physics, the man is really in the 

 situation of a bottle of water which is charged with carbonic acid gas 

 to obtain artificial Seltzer water. 



When he rises to the surface, if the decompression is not gradual 

 enough, the gases with which the blood is supersaturated tend to es- 

 cape with effervescence. Now experimenters who make injections into 

 the venous system of horses, for example, know that if they intention- 

 ally allow a small bubble of air to enter with the liquid injected, as 

 soon as this bubble of air penetrates the cerebral circulation, the 

 experimental animal falls as if struck by lightning. The effect, in this 

 case, is only momentary, but if the quantity of bubbles of air ad- 

 mitted is great, death occurs very soon. 



We have thought it best to quote in full this noteworthy passage 

 which recalls what M. Bucquoy had already said (see page 459), 

 and which contains in the form of a hypothesis an exact description 

 of what really takes place, as we shall show in the second part of 

 the present book. But by a strange inconsistency, which shows 

 what influence the old ideas about the mechanical effect of the 

 decompression had gained over the best intellects, M. Leroy de 

 Mericourt, instead of adhering to the idea of intravascular gaseous 

 obliterations, remains imbued with the hypothesis of hemorrhages, 

 resulting from the forcing back of the blood. He then asks himself 



