Theories and Experiments 215 



it adds to the elastic power of the arteries, that it condenses the walls 

 of these same vessels, and resists the transudation of the more subtle 

 parts, the nervous fluid, for example, and that for all these reasons 

 it must contribute to the muscular strength. 



If then one were suddenly transported from sea level merely to 

 the altitude of 1250 fathoms, where the weight of the air lifts only 

 about 21 inches of mercury, the action of the atmosphere upon our 

 body would be lessened one quarter, or 5508 pounds, 7 ounces; con- 

 sequently all the effects of this action would be considerably lessened, 

 and the muscular powers would necessarily suffer from it. The ves- 

 sels, in particular, would exert very much less pressure upon the fluids 

 which they contain; and for that very reason they would interfere less 

 with the acceleration which muscular movement tends to give to the 

 whole mass of our liquids. 



And so in lofty regions where the vessels are only slightly com- 

 pressed by the pressure of the atmosphere, the efforts one makes in 

 climbing a steep slope must accelerate the movement of the blood much 

 more than in low lands, where the compression of the vessels resists 

 this acceleration. From that, no doubt, result the rapid throbbing of 

 all the arteries and the palpitations which attack one on lofty moun- 

 tains, and which make one fall unconscious if he persists in moving 

 with too much speed. 



But also, through an effect of this same relaxing of the vessels, 

 since they react weakly upon the blood, as soon as one ceases moving, 

 the acceleration which had been produced by this movement ceases of 

 itself shortly, whereas if the vessels were greatly strained, their elas- 

 ticity would have perpetuated this acceleration, long after its cause 

 had ceased to act. That is the characteristic of weak beings, they are 

 easily moved, and quieted too; whereas strong beings, hard to set 

 in motion, are also harder to quiet. When, therefore, the vessels are 

 relaxed by the decrease of the air pressure, a few moments of rest 

 are enough to establish order and calmness in the circulation, and by 

 the slackening of this circulation to give a feeling of inner coolness, 

 which, aided by the coolness of the air which one breathes in these 

 lofty regions, brings complete calmness, and persuades one that the 

 fatigue has completely vanished. As to the drowsiness, I think that 

 it is the effect of the vascular relaxation, and especially that of the 

 brain. At least this seems to me the most probable reason for these 

 facts: I leave judgment of it to the professional physiologists. (Vol. 

 I, p. 482-488.) 



And so to de Saussure it is the decrease of the pressure exerted 

 by the air upon the cutaneous vessels which, by lessening their 

 resistance to the heart impulses, causes the circulatory acceleration 

 and consequently all the symptoms which he observed and experi- 

 enced. But, after his celebrated ascent of Mont Blanc, he adds to 

 this explanation reflections of a value in much greater harmony 

 with the wisdom of his lofty intellect: 



1965. — If we consider after all (he says) that the barometer at 

 that height stood at only sixteen inches and one line, and that there- 



