Theories and Experiments 239 



gas; but that is a mistake, for many Mongols from Tsaidam remain 

 there during the summer with their cattle, which would not be pos- 

 sible if asphyxiating gases escaped there .... Father Hue should not 

 be believed when he speaks of the harmful gases of Burchan-buda. 

 (P. 174.) 



Dr. Pravaz, 73 a physician of Lyons, a few years before, had 

 founded an establishment in which he used a stay in compressed 

 air for the treatment of different diseases. The book which he 

 devoted in 1850 to the exposition of the data which he had ob- 

 served contains, in its first part, interesting remarks on the different 

 causes of mountain sickness: 



1. Respiration is mechanically restrained in its extent by the lack 

 of elasticity of the atmosphere, which presses upon the interior of the 

 lungs and by itself causes their development when the thorax expands 

 through the effort of the inspirating muscles. 



2. This function is insufficient for hematosis, because the oxygen, 

 or the vivifying principle of the blood, is present in too small an 

 absolute quantity in the volume of air introduced by each movement 

 of the inspiration, in addition to the fact that the lack of pressure 

 makes the quantity of this gas dissolved in the blood less abundant. 



3. The arterial circulation is accelerated as a result of the rapidity 

 of the respiratory movements caused by the instinct of self-preserva- 

 tion, while the capillary circulation slackens, because the recall of the 

 venous blood to the right cavities of the heart has become less ener- 

 getic on account of the decrease of the constriction exerted on the 

 periphery of the organs. (P. 57.) 



Farther on, while discussing at length these congestions of the 

 mucous membranes which have attracted so much attention from 

 the observers, he explains them by saying: 



One of the motors of the venous circulation, and consequently of 

 the capillary circulation, namely, the atmospheric pressure, decreases 

 as one rises above sea level. The greater the altitude, the less active 

 will the recall of the blood into the right cavities of the heart be, 

 and the greater tendency will the blood have to congest the parts 

 where aspiration is ordinarily most effective. We may then compare 

 the action of the heart with that of a pump working in a medium 

 where the air is very much rarefied, and which can draw water only 

 at a depth much less than under the ordinary pressure of the atmos- 

 phere .... 



Hence the tendency to hemorrhages and apoplexy on lofty moun- 

 tains. 



Mountain sickness presents another symptom which no one has 

 tried to explain physiologically. It is evidently produced by a disturb- 

 ance of the circulation in the portal vein system; it is characterized, 

 in fact, like congestions of the liver and the abdominal viscera, by 

 vomiting, cramps in the stomach, and intestinal pains. (P. 82.) 



