Theories and Experiments 485 



Then appear the cases of epistaxis and hemoptysis, sometimes passing 

 or fatal apoplexies, accompanied in certain cases by temporary or 

 permanent hemiplegias, and finally these fleeting or persisting para- 

 plegias, which M. Barella observes in laborers working in caissons, and 

 which, according to M. Leroy de Mericourt, would be one of the most 

 common causes of death in sponge fishermen. 



This explanation, however, does not satisfy M. Bouchard, who 

 then quotes the ideas of MM. Rameaux and Bucquoy on the gases 

 of the blood: 



But this sudden congestion, at the time when the blood flows 

 back from the abdomen towards the other organs, is perhaps not the 

 only cause or the real cause of these hemorrhages, or at least of a 

 certain number of them: of those, for example, which take place in 

 the incompressible cavities, the skull and the spine. Another inter- 

 pretation has been given, which seems probable. Gases are dissolved 

 in liquids in proportion to their tension; the blood of a man who has 

 remained for several hours under a pressure of four atmospheres 

 should therefore contain a much greater proportion of carbonic acid 

 than in the normal state; and this dissolved carbonic acid will re- 

 turn to the gaseous State as soon as the outer pressure lessens. If 

 the decompression takes place slowly, the blood as it passes through 

 the lungs, can release the surplus carbonic acid, and no symptom will 

 appear; but if the decompression is sudden, the carbonic acid will 

 tend to break out in gaseous form even into the vessels, and by its 

 sudden expansion, or by the obliteration of small vessels in which it 

 cannot circulate, will cause ruptures and extravasations. (P. 99.) 



M. Bouchard applies this idea to the formation of painful mus- 

 cular swellings, of which the authors whom we have previously 

 quoted have spoken: 



These swellings are not inflammatory, they are not exudates nor 

 extravasations. They disappear immediately simply through return 

 to compressed air, and are never followed by ecchymotic spots. When 

 the swelling exists, it is not accompanied by throbbing or redness, so 

 that we can hardly attribute it to an exaggerated arterial dilatation, 

 as M. Foley has done. If it is true that muscular labor is an important 

 source of carbonic acid, might we not assume that the muscles which 

 have exercised most are laden with carbonic acid dissolved in the 

 very tissue, and that, at the time of decompression, this acid is liber- 

 ated in gaseous forms, and then is redissolved by a new compression? 

 (P. 101.) 



We now have to speak of an author who wrote after our first 

 personal researches; but we place him here because he seems to 

 have given little heed to the experiments which we had already 

 published. 



After reporting the data which he observed, the summary of 



