Decreased Pressure 995 



of animals with constant temperatures, they would not have been 

 able to release the necessary increase of tension strength, and 

 consequently they would have had to deduct from the production 

 of heat the vital force necessary to execute this work. Now it is 

 possible that even at the limit, when the temperature still remains 

 normal during rest, there is a slight drop in it at the moment of 

 the new expenditure required by the vertical propulsion of the 

 body. I cannot stress too strongly the interest which would be 

 presented by thermometric researches carried on, with all neces- 

 sary precautions, and during the act of ascent, upon persons already 

 suffering severely from mountain sickness; but perhaps our Euro- 

 pean mountains are not high enough to permit us to observe a drop 

 of temperature, even in these conditions. 



It has been thoroughly demonstrated, at any rate, that chilling 

 of the body is not the cause of mountain sickness, which occurs 

 without modification of the inner temperature. 



I do not mean, as I have observed in speaking of aeronauts, that 

 exterior cold plays no part in the matter of mountain sickness. 

 On the contrary, its importance is great because it increases the 

 oxygen requirements of the organism which is struggling to pre- 

 serve its equilibrium. Indeed it is evidently this necessity of 

 struggling against cold, a new cause for the consumption of oxygen, 

 a new cause for the impoverishment of the blood, which explains 

 why, in our icy Alps, mountain sickness strikes most travellers at 

 heights which are quite harmless in the Cordilleras; here, the limit 

 of perpetual snows is 4800 meters; there, only 2700. Provision 

 must be made for warming the body at the same time as for the 

 muscular efforts of the ascent. 



B. Duration of the Ascent. The duration of mountain journeys, 

 much longer than that of balloon ascensions, is a favorable con- 

 dition, as we said when speaking of the ascensions. The traveller, 

 compelled to mount the slopes slowly, avoids the harmful effect 

 of sudden modifications in the oxygen content of the blood; he can 

 hardly in a day's march mount more than 3000 meters, and then, if 

 he has not reached the summit, he must rest, pass the night, in a 

 word, become accustomed to the state of anoxemia he has reached. 

 This is so true that in the first part of this book we could have 

 explained a part of the peculiarities of mountain sickness in the 

 different regions of the globe by the form of the mountain mass, 

 or the more or less isolated situation of the peak to be climbed. 



We have also shown how a better use of muscular strength, due 

 to the habit of exercise in the mountains, explained the much 



