254 Historical 



compensates for the lessened proportion of oxygen in the air inspired 

 is not valid. Anyone who has himself experienced the short and hasty 

 inspirations, without proper expansion of the thorax, which accom- 

 pany the breathlessness during and immediately after an ascent, 

 realizes that these hasty inspirations cannot have the calorific effect 

 of regular inspirations. So panting ceases the moment one stops walk- 

 ing, and a regular respiration, more frequent than on the plain, partly 

 compensates for the lessened quantity of oxygen; I say partly, for to 

 make complete compensation, on the Grand-Plateau, for example, the 

 number of inspirations would be to the number on the plain as 8 is 

 to 5, that is, proportional to the quantities of oxygen inspired. Now 

 that is not the case; panting, in a state of rest, certainly does not add 

 one-third more. The lessened oxygenation of the blood is therefore 

 not counterbalanced by the frequency of the inspirations, and becomes 

 a physiological cause of cold which is peculiar to lofty regions, and 

 probably the principal one of all those causes which bring on the 

 symptoms known under the name of mountain sickness. 



This explanation, we see, is only the one already envisioned by 

 de Saussure; we see also that M. Martins is much less optimistic 

 than Longet, who asserted that on the mountains one could make 

 up for the lessened oxygen content of the inspirations by their 

 number. 



The same ideas also occur to the mind of Guilbert, !U when he 

 gives an account of the soroche of the Cordilleras: 



Upon the plateau of the Cordilleras, the air contains only 3/5 of 

 the quantity of oxygen which it contains at 0.76. When one ascends, 

 he reaches colder and colder regions, where man must produce more 

 heat, to maintain his normal temperature. To expedite combustion, 

 he needs a greater quantity of oxygen, and the air contains less. 

 Here are two causes working in the same direction, which are suffi- 

 cient to explain the disturbance of the respiration and the circulation. 



The experiments of Magnus have shown the presence of free 

 gases in the state of solution in the blood. The tension of these gases 

 increases as the pressure diminishes. Then these gases exert a 

 pressure against the walls of the vessels in which they circulate with 

 the blood, and distend them; hence come compression of the brain, 



and consequently violent pains in the head, etc Perhaps too 



hematosis is incomplete; in this case, it could claim part of the effect 

 on the nervous system; the blood, which has lost part of its stimulating 

 qualities, could no longer be a sufficient stimulus; hence the tendency 

 to syncope, etc 



The decrease of the atmospheric pressure also explains the 

 hemorrhages. The free gases of the blood press against the walls of 

 the vessels; a moment may come when these walls, unable to resist, 

 longer, are ruptured and let the blood escape 



The action of the heart is no longer counterbalanced by the 

 atmospheric pressure, and the result is a stasis of blood in the capil- 

 laries which are therefore distended. This phenomenon is evident 



