1030 Summary and Conclusions 



symptoms of anemia can be attributed to these high pressures. 

 But the symptoms of decompression complicate matters so that it 

 is impossible to make any statement. 



But if the necessities of industry bring the use of pressure above 

 5 atmospheres, we can expect to see appearing in the workmen 

 symptoms the severity of which will increase rapidly; at 10 atmos- 

 pheres, I do not doubt that death will be frequent, and of course 

 I am speaking here only of the period of compression. 



If the importance of this work is enough to justify great expense, 

 and such a case might present itself, for example, for pearl fishers, 

 or divers for sponges and especially coral, or men in divers' suits 

 engaged in salvaging valuable articles, the difficulty may be man- 

 aged: since the increase in the tension of the ambient oxygen con- 

 stitutes the danger, this tension must be lessened so that it varies 

 always somewhere between the normal amount of 21 and that of 

 60, which seems harmless. To reach it, the caissons would have 

 to be filled, not with ordinary air, but with air of low oxygen con- 

 tent. The apparatus with which M. Tessie du Motay prepares 

 oxygen could be used here; one could get from it, in fact, nitrogen 

 containing only very little oxygen. By mingling this nitrogen 

 with ordinary air in suitable proportions, one could easily secure 

 the desired proportions: at 8 atmospheres, for instance, to bring 

 the oxygen tension to 40, one would require air containing only 

 5% of oxygen. Hydrogen could also be used, and we know that 

 M. Giffard prepares it today at very moderate prices. 



But if we imagine these serious difficulties overcome, we shall 

 find ourselves facing the dangers of decompression, greatly ag- 

 gravated by the enormous proportion of nitrogen which will be 

 dissolved in the blood. Accidents are frequent now, as we have 

 seen, even with ordinary air. But in the case of compression with 

 ordinary air, the only type which we have dealt with as yet, our 

 researches have brought us very important and very practical 

 conclusions. 



As soon as the pressure employed has reached 2 atmospheres in 

 total pressure, close watch should be kept; there is as yet no true 

 danger, but already local pains appear, and besides, it is wise to 

 accustom the workmen to precautions early. The great precaution 

 is slowness in decompression. 



I think that between 2 and 3 atmospheres, a half-hour should 

 be given to the decompression, to be perfectly safe; from 3 to 4 at- 

 mospheres, one hour, and the slowness of the decompression will 

 have to be assured by the degree of opening possible in the equi- 



