500 Historical 



to 12 minutes; finally, nothing was said of the diet to which the 

 subject of the experiments was limited. 



The increase in the quantity of carbonic acid exhaled in com- 

 pressed air, admitted without argument by Pravaz, M. Foley, and 

 the German physiologists, led them to conclude that a greater 

 quantity of oxygen was absorbed even during the compression. 

 Hence a whole series of conclusions, already glimpsed by the earlier 

 authors: nervous stimulation, muscular energy, combustion of the 

 tissues are easily deduced from it. Hence the increase in the quan- 

 tity of urine excreted (?), the slight rise in temperature (?), the 

 insatiable appetite, which causes an increase in weight if it can 

 be satisfied, and a loss of weight under opposite conditions. All 

 that links up very well, one must admit; but the method which 

 bases the accuracy of the premises upon their harmony with the 

 conclusions is a very dangerous one: it never proves anything to 

 the mind of an experimenter. Therefore I do not dwell upon these 

 data, all the details of which I have given above. 



B. Phenomena Due to the Decompression. 



Physicians who have attended caisson workers and divers work- 

 ing in suits have been unanimous in attributing to congestions of 

 the blood, sometimes going as far as hemorrhage, the symptoms 

 following decompression: congestion of the lungs, the abdominal 

 viscera, and particularly the encephalic and spinal nervous centers. 

 But they have not clearly determined the method of producing 

 these congestions, far from it. 



Pol and Watelle believe that the congestion is produced during 

 the very act of compression by the centripetal driving back of the 

 blood; if it does not produce its effect then, it is because the super- 

 oxygenated blood has no harmful effect upon the organs. At the 

 time of decompression, the blood loses oxygen, and the usual con- 

 sequences of congestion appear (page 452). I confess I do not 

 understand very well how the physicians of Douchy could reconcile 

 their theory with the cases which they observed themselves in 

 which the most serious symptoms existed at the exact time when 

 the venous blood was brilliantly red. 



M. Foley, in his explanation of the "post-caisson congestion," 

 is so vague that I prefer to refer the reader to the word-for-word 

 quotations which I made from his memoir (page 463). Babington 

 and Cuthbert (page 466) do not express themselves much more 

 clearly: in their opinion, the protection of the skull and the spinal 

 column would prevent, at the time of the decompression, "the 



