1000 Summary and Conclusions 



all these circumstances being procured most satisfactorily by so- 

 journ in the mountains. 



Great heights. But let us suppose our traveller transferred sud- 

 denly from the seashore not to Chamounix (1020 meters; 67 cm.) 

 or to Davos (1650 meters; 62 cm.), but to La Paz (3720 meters; 48 

 cm.) , or especially to Cerro de Pasco (4350 meters; 44 cm.) . If he 

 had, according to our usual hypothesis, 20 volumes of oxygen in 

 his arterial blood and 12 in his venous blood, and nothing else was 

 changed in him, he would have no more than about 16 or 14 

 volumes in the arterial blood, with 8 or 6 in the venous blood. 

 We have seen in the first part that, without the slightest doubt, at 

 Cerro de Pasco, especially if the action of the cold intervenes, he 

 will be attacked by the soroche (mountain sickness) , whose sever- 

 ity will be increased when he tries to walk, climb, or, like d'Orbigny, 

 waltz. The calculations which we made in the preceding section 

 in regard to mountain travellers, will give us a sufficient account 

 of these symptoms. 



But very likely he will seem to become habituated progressively 

 to this state of affairs, especially at La Paz; after some time, he will 

 no longer feel the soroche when he is in a state of repose, and will 

 experience its disastrous effects only if he indulges in violent exer- 

 cise. He may even escape these entirely; he is, or seems to be, 

 as they say, acclimated. Is something changed in him then? 



We might ask first whether, by a harmonious compensation of 

 which general natural history gives us many examples, either by a 

 modification in the nature or the quantity of hemoglobin, or by an 

 increase in the number of the red corpuscles, his blood had become 

 qualified to absorb more oxygen under the same volume, and thus 

 to return to the usual standard of the seashore. The dark color of 

 the blood observed formerly by Dr. Jourdanet during surgical oper- 

 ations would not be a positive objection to this hypothesis, since 

 we have seen that the red color of the blood depends not on the 

 quantity of oxygen it contains, but on the proportion between this 

 quantity and that of the hemoglobin. But it is very certain that 

 such a change, if it takes place, requires a very long time; it is even 

 probable that it can come about only through inherited disposi- 

 tions, and can come to complete development only at the end of 

 successive generations, so that it would explain the acclimatiza- 

 tion, not of the individual, but of the race. But even in this case it 

 is far from being proved; let us add that it would be desirable and 

 very easy 2G to test by direct experiment the hypothesis which I 

 propose without having any great confidence in it. 



