236 Historical 



of slightly expanded air upon respiration. He gives no informa- 

 tion about the manner in which he carried on his experiments, 

 which dealt only with pressures included between 340 and 330 lines 

 of Paris (767 and 744 mm.) . 



Their chief purpose was to find out whether variations in pres- 

 sure have an effect on the exhalation of carbonic acid; their results 

 are not very clear, in spite of the profusion of tabelles in which 

 they are expressed and the wealth of decimals of doubtful deriva- 

 tion which accompany each number. All conclusions based on these 

 experiments would seem to me extremely rash. Besides, the slight 

 barometric oscillations within the limits of which they are kept 

 prevent them from having any interest for us. 



It was also at this same period that M. Lepileur's C9 memoir 

 appeared, the interesting narrative of which we have quoted in the 

 proper place and in considerable detail (See page 98 et seq.). This 

 work is not only rich in precise and shrewd observations, but it also 

 contains theoretical views, the importance of which deserves our 

 full attention. M. Lepileur first gives credit to the explanations of 

 de Saussure and those of Brachet; but they do not satisfy him: 



The phenomena relating to hematosis do not seem to us the only 

 causes of the panting and lassitude on lofty mountains .... 



One gradually becomes used to the rarefied air so that he no 

 longer feels its effect. If it depended only on the more or less com- 

 plete stimulation of the muscles by a blood which is more or less 

 arterial, would this fatigue be accompanied by pains of back and 

 limbs, and would it be likely to disappear thus through habit in so 

 short a time? 



We should be tempted to consider this painful fatigue as resulting 

 chiefly from the congestion of blood taking place in the muscles during 

 their action, in proportion to their efforts, and the whole group of 

 phenomena due to the rarefaction of the air seems to us to agree fairly 

 well with this idea. The more active the circulation is, the more easily 

 congested the organs are. Now the pulse, without losing strength, 

 becomes considerably more rapid when one is ascending a mountain, 

 and the tendency to congestions is completely demonstrated by the 

 facts which we have given .... When one remains motionless, equi- 

 librium is maintained .... but as soon as one begins to move, the 

 contracted limbs become the seat of a congestion which occurs with 

 a rapidity proportional to the increase in the speed of the circulation. 

 (P. 62-64 of the separate printing.) 



Beside the congestion of blood in the muscles, which, according 

 to him, explains the lassitude, M. Lepileur places exertion, which 

 would explain the nausea, the impending syncope, and the head- 

 ache: 



