256 Historical 



After explaining thus the chief condition of the physico-physio- 

 logical problem, M. Jourdanet states that the ardor of the sun on 

 the heights of Anahuac must also act to diminish considerably the 

 density of the strata of air near the ground, and consequently the 

 intrapulmonary gaseous endosmosis. 



When this has been established, he shrewdly compares respira- 

 tion in a pure air, but under low pressure, with respiration in air 

 with low oxygen content, but at normal pressure. Then answering 

 the objection taken from the work of MM. Regnault and Reiset 

 by M. Gavarret, an objection which had just found new strength 

 in the experiments of M. Fernet, he comments with reason that if 

 the chemical combination of the oxygen and the blood was abso- 

 lutely independent of pressure, one should live with ease not only 

 at the lowest barometric pressures, but also in air with very low 

 oxygen content, which no one will admit: 



According to the opinion of M. Gavarret himself, the solubility 

 of oxygen in the blood is diminished when the quantity of oxygen 

 inspired is lessened. It is therefore indisputable that, however effec- 

 tive and necessary the affinity of the corpuscles for oxygen in the 

 act of respiratory endosmosis may otherwise be, the mere fact of the 

 rarefaction of this gas lessens the absorption of it at high altitudes 

 and thus causes real disturbance in the phenomena of respiration. 

 (P. 69.) 



M. Jourdanet then adds the following interesting observation: 



If the convictions which we have just expressed were to be shown 

 inaccurate in the results, compensation for the rarefaction and the 

 lightness of the atmosphere in Mexico would have to be made by 

 deep inspirations and by a respiration which in general was more 

 active than at sea level. It is commonly believed that this is the case 

 and this opinion is based upon the observation furnished by persons 

 who make a rapid ascent in the atmosphere or who make only a 

 short stay at high altitudes. It is completely erroneous. The truth 

 is that those who dwell at great elevations breathe less quickly than 

 men whose abode is near sea level. The rarity of the air, as we shall 

 see later, produces apathy of the muscular system. The chest also 

 feels its effects. I have often surprised the functions in the very act 

 by counting the respiratory movements of persons who were unaware 

 of it and who were in a state of complete repose. I almost always 

 noted a decrease in the number of expansions of the chest. Some- 

 times, fairly often, in fact, one forgets to breathe and is forced to 

 make up for lost time by taking deep inspirations. (P. 76.) .... 



But this respiration, so calm in absolute repose, easily gains 

 amplitude under the influence of movement. (P. 87.) 



The consequences of this decreased absorption of oxygen are 

 easily foreseen. The first is a decreased activity in the production 



