252 Historical 



sened quantity of oxygen contained in expanded air, of equal 

 volume: 



MM. Barral and Bixio, .... in spite of the fact that more than 

 9000 kilos were taken from the pressure to which their bodies were 

 accustomed, felt no very pronounced sensation .... On the other 

 hand, workmen in diving bells endure a double, triple, or even 

 quadruple pressure without serious change in the functioning of the 

 organs; and by this we are naturally led to consider the differences 

 of atmospheric pressure as less important than one would be inclined 

 to think from the purely scientific point of view. 



On the other hand, we have recognized that as one ascends 

 heights, the air becomes less dense and consequently contains less 

 oxygen, so that the respiration must be more frequent and more com- 

 plete to bring into the lungs the quantity necessary for the oxygenation 

 of the blood. From this physiological necessity there must result a 

 considerable difficulty in breathing and consequently in the circulation 

 also; and this we see in the dwellers in the lofty regions of our globe. 



Yet we must not believe that the rarefied air of our mountains 

 does not contain a sufficient proportion of oxygen to maintain life; 

 experiments made on the quantity of oxygen necessary for respira- 

 tion have, in fact, shown that a man at rest in one hour converts 50 

 grams into carbonic acid, and if we add five or even ten grams for 

 the increase produced by movement or work, we shall see that, 

 assuming that the stay is in a place where the barometer stands at 

 only 315 mm. (7000 meters), the air still contains 100 grams of oxygen 

 in the 800 liters that a man breathes per hour. So that we see 

 definitely that, even at great heights, the atmosphere can furnish man 

 a sufficient quantity of oxygen to sustain breathing. 



Does it follow, nevertheless, that this great decrease in an element 

 so essential to life has no effect upon our principal functions? We 

 do not think so, quite to the contrary; it is visibly evident that the 

 withdrawal of a considerable portion of oxygen must make respiration 

 incomplete and react upon the other vital functions which, like the 

 circulation, are very intimately associated with respiration. 



But even that is not all; when an incompletely oxygenated blood 

 reaches the different organs, such as the brain and the muscular 

 system, it is evident that their functions will experience a disturbance 

 proportionate to the incompleteness of the oxygenation; so that one 

 must attribute to the decrease of oxygen a considerable portion of the 

 disturbances which occur in innervation and motility. (P. 47.) 



M. Lombard then admits in part the explanation which the 

 Weber brothers had given and which von Humboldt had accepted 

 in regard to the role of the pressure on the cotyloid cavities. 



Among the symptoms experienced by travellers attacked by 

 mountain sickness, the sensation of extreme cold is neither the 

 least strange nor the least painful. M. Ch. Martins,™ who had felt 

 it in his ascent of Mont Blanc in the company of Bravais and M. 

 Lepileur, made a special study of this physiological cold, an 



