Decreased Pressure 993 



to ascend by a series of efforts requiring a consumption of oxygen. 

 Since the research of Claude Bernard, corroborated by that of Lud- 

 wig and Sczelkow, we know that there is a difference of about 12 

 volumes per cent of oxygen between the arterial blood entering 

 a muscle and the venous blood leaving it during the contraction, a 

 difference that amounts to only 8 volumes while the muscle is at 

 rest. If then we suppose that all the consumption of the oxygen 

 of the traveller's blood is due to muscular metabolism which is 

 increased in the proportion of 8 to 12, the venous blood should 

 contain only 12: 8 = 8: x = about 5 volumes of oxygen; at 5100 

 meters, the oxygen content of the venous blood should fall from 

 6 to 4, as the muscles pass from the state of repose to the state of 

 general contraction; at 6600 meters, it would be reduced to 1.3; and 

 all we said above about the difficulty of dissociating the weakly 

 oxygenated combinations of the hemoglobin, shows the dangerous 

 consequences of this exhaustion which our calculations show must 

 take place. Either the exhaustion will be complete, and then the 

 blood which returns to the right heart will be entirely stripped 

 of oxygen and the respiratory exchanges will restore to the arterial 

 blood only a quantity of oxygen that is still less than what was 

 there after the period of rest; or the exhaustion will be hindered 

 by chemical difficulties, and then the muscle, not being able to 

 find a sufficient quantity of oxygen, will stop in its contraction. 

 For one or the other reason, the traveller, after a few steps, is 

 forced to stop immediately, under pain of asphyxia: so he stops, 

 and the venous blood which leaves the muscles in repose, still con- 

 taining a considerable quantity of oxygen, can go into the lungs 

 to take up what the physico-chemical law of dissociation permits 

 it to take into the expanded gaseous medium. When the percentage 

 has risen sufficiently, a new effort is possible, followed soon by 

 another halt. This has happened to all travellers in lofty regions, 

 as the data reported in the historical part of this book prove super- 

 abundantly. 



Of course the calculations which we have just made give exag- 

 gerated results in this sense, that the body is not all muscles, and 

 that not all the muscles contract at once in the act of ascent. But 

 on the other hand, we have spoken only of static muscular con- 

 traction, without taking account of work to be done. Now it is 

 probable, without our being able to consider this allegation as 

 demonstrated today, that a muscle which produces work while it 

 contracts consumes more oxygen than a muscle which contracts 

 statically. 



