222 Historical 



I should note that the inhabitants of Koonawur estimate the height 

 of mountains by the difficulty in breathing during the ascent of them, 

 which difficulty they attribute to a poisonous plant; but in spite of 

 our search in each village, we found no one who ever knew this 

 plant, and judging by our experience, we are inclined to attribute 

 these effects to the rarefaction of the atmosphere, for we have ex- 

 perienced them at elevations where there was no more vegetation. 

 (P. 49.) 



He alludes again to this hypothesis in his book on the country 

 of Koonawur, 34 but always to reject it: 



Travellers crossing these ranges attribute these painful effects to 

 the influence of poisonous plants; but better informed persons, who 

 customarily pass over these heights where there is no vegetation, 

 know very well that they are produced entirely by the altitude. (P. 

 37.) 



But in narrating his expedition and his stay at the pass of 

 Shatool (4830 meters), Dr. Gerard 3 " does not give any heed to 

 the explanation of the natives. He suffered greatly, as the account 

 which we reported above proves, and naturally sought the cause of 

 his distress, but without success; but in the meantime, he opposed 

 the skepticism of those who for some reason experienced no symp- 

 toms: 



There I had a lesson which I shall never forget, and I am sure 

 that a man of a more plethoric constitution would have died from 

 apoplectic suffocation. The blood left my extremities, and the pres- 

 sure on the surface of the body was so diminished in that rarefied 

 air that the blood rushed to the head and produced vertigo. (P. 308.) 



The cause of the symptoms is not very easily seen, and these 

 extraordinary indications of loss of strength, distress, and mental 

 weakness are not satisfactorily explained, and although we cannot 

 hesitate to attribute the principal and immediate cause of them to 

 the rarity of the air, or, more exactly, to the diminished pressure, 

 by which the balance of the circulation is destroyed, nevertheless, the 

 effects are so capricious and irregular that they can hardly agree with 

 the idea of a constant cause. This leads travellers even to deny the 

 existence of the symptoms, and those who have by chance resisted 

 this effect while crossing the mountains remain firm in their convic- 

 tion; but I know that you will believe my reports, although you had 

 only a headache on Boorendo. I too passed the night here without 

 any symptom, except weakness. (P. 320.) . . . 



As respiration cannot take place in a vacuum, we must consider 

 that, at the elevation of 18,480 feet (5630 meters), the air is nearly 

 half exhausted, and as the whole can have only the sum of the effects 

 of its parts, the progressive action here becomes an arithmetical series, 

 reducible to an experiment in physics, in which the piston strokes of 

 a pneumatic pump seem to draw the hand placed over the opening 



