112 Historical 



minute. While I was climbing from Chamounix to Mont Blanc, it 

 increased progressively, following the altitudes, to 80, 108, 116, 128, 

 136; and finally, while I was climbing the last ridge which leads from 



Fig. 1— Lortet. Respiratory tracing taken at Lyons (200 m.) 



Fig. 2 — Lortet. Respiratory tracing taken at the top of Mont Blanc (4810 

 m.) after an hour's rest. 



the Bosses-du-Dromadaire to the summit, to 160 and sometimes more. 

 These ridges, it is true, are very steep, they have a grade of forty-five 

 to fifty degrees; but slowness of the walking is very great. One 

 generally takes thirty-two steps per minute and often much less when 

 steps have to be cut constantly. The pulse is feverish, hasty, and weak. 

 It is plain that the artery is almost empty. The slightest pressure 

 stops the current in the blood-vessel. The blood must pass very 

 rapidly in the lungs, and this rapidity increases still more the insuffi- 

 cient oxygenation which has already resulted from the rarefaction of 

 the air. It does not have time to receive the oxygen adequately, and 

 neither does it have time to give off its carbonic acid entirely. Above 



