Increased Pressure 1025 



the arterial blood is not completely saturated with oxygen, 

 although its oxygen content is greater and greater in proportion as 

 we rise above normal pressure. 



It is very important for the doctor and the hygienist to study 

 these low pressures, because they are the ones used in therapeutics 

 on the one hand, and in industry on the other. But from my point 

 of view, what seemed most interesting was to find out at what 

 pressure the maximum of intra-organic oxidation took place. We 

 have seen, on the one hand, that from the lowest pressures up to 

 one atmosphere, and on the other hand, beginning with five or six 

 atmospheres and above, these oxidations continue to lessen: where 

 would be the top of the curve which represented these phenomena? 



Now my direct analysis of the quantity of carbonic acid ex- 

 haled, of oxygen absorbed, and of urea secreted in a given time, 

 and my indirect researches on the rapidity of putrefactions tend 

 to show that it is in the neighborhood of three atmospheres, about 

 the oxygen tension of 60 that the maximum we are seeking is found. 

 The recent experiments of G. Liebig give the same evidence. 



But I am the first to recognize that nothing is more difficult 

 than such experiments, and that conclusions are always dangerous. 

 In regard to the production of urea, for example, either we must 

 keep the subject on a very regular diet, and then the excess of 

 oxidation, if there is one, working on the materials of the organism 

 itself, will cease to appear upon exhausting them; or we must 

 increase the amount of food, and then the increase of urea pro- 

 duced will no longer have any possible measure, because we do 

 not know the equivalent in urea of the different foods: upon this 

 last point I have begun researches which are still incomplete. 

 But in spite of all these causes of error, I am struck by the agree- 

 ment of the analyses of Vivenot, Panum, G. Liebig, and J. Pravaz 

 with mine, and also by the unanimous testimony of doctors and 

 engineers on the increase of the appetite of patients or workmen 

 subjected to compressed air. My conclusions then seem to me at 

 least very probable. 



It would follow, if we consider the higher animals, that organic 

 oxidations will increase in intensity as we approach the saturation 

 of the hemoglobin. We can imagine that the maximum point will 

 be where the oxidation takes place most easily, where the last 

 molecules of oxygen are hesitant, so to speak, hardly retained by 

 the hemoglobin, ready to leave it to combine with the tissues; 

 beyond this point, as we saw above, the oxidations lessen. 



But on the other hand, the behavior and the speed of develop- 



