1016 Summary and Conclusions 



production of urea: the greatest deviations are, in the rectum, of 

 0.34°. 



I refer to the original article for the reading of the explanations 

 which M. Pravaz gives of the variations in the nutritive phenomena 

 which he thinks he has observed. Personally, I consider that a 

 single experiment does not permit one to draw conclusions, and 

 that one should suspend judgment on the question of whether the 

 combustions really increase only during the first moments of the 

 stay in compressed air. As for the observations which embrace the 

 24 hour period, the first should be eliminated, since the diet was 

 not regulated. For the two following, no precautions were taken 

 in regard to muscular work: "exercise," says M. Pravaz himself, 

 "was necessarily variable from one day to another, and gave rise to 

 changes in the production of urea, which might introduce into the 

 problem an undeterminable unknown" (p. 43) ; one should there- 

 fore take no account of it. Finally, the fourth presents irregular- 

 ities which seem to take away all value from the averages he 

 strikes; during three hours fasting, the quantities of urea obtained 

 were: 



First day Normal pressure 3.0075 gm. 



Second day 10 cm. compression 3.1933 gm. 



Third day 19 cm. compression 3.6990 gm. 



Fourth day__ ___ 38 cm. compression __ 3.5685 gm. 



Fifth day 57 cm. compression 3.2711 gm. 



Sixth day 76 cm. compression 3.7507 gm. 



Seventh day Normal pressure 3.3963 gm. 



We see, besides, that the maximum of production coincided 

 with the highest pressure, which does not agree with the opinion 

 of the author. 



Without dwelling any longer on this critical analysis, I quote 

 the general conclusion of M. Pravaz: 



If we examine from a general point of view the effects of increase 

 of atmospheric pressure on the animal economy, we are led to dis- 

 tinguish in the action which compressed air exerts two elements: the 

 pressure element and the superoxygenation element. 



From the pressure or mechanical element rise principally the 

 modifications produced in the rhythm and amplitude of the respi- 

 ration. 



The modifications experienced by the circulation and the nutrition 

 are the result of the conflict carried on between the super oxygenation 

 element and the pressure element, the first tending, by the super- 

 activity it gives to the chemical phenomena going on in the tissues, to 

 increase the production of urea and carbonic acid, from which come 



