Page:Whymper - Travels amongst the great Andes of the equator.djvu/14

vi general, leading features. Nausea and vomiting; headaches of most severe character; feverishness; hemorrhages; lassitude, depression and weakness, and an indescribable feeling of illness, have been repeatedly mentioned as occurring at great elevations, and have only been cured by descending into lower zones. To these maladies the term Mountain-sickness is now commonly applied.

It is very generally admitted that mountain-sickness should be attributed to the diminished atmospheric pressure (or, as it is termed, to the rarefaction of the air) which is experienced as one goes upward. Yet, in various parts of the world, the notion is, and has long been entertained that it is due to local causes, such, for example, as noxious exhalations from vegetation. Some support to this notion seems to be found in the fact that whilst the greatest heights in Europe (15–16,000 feet) are annually ascended by throngs of persons without perceptible inconvenience, multitudes of others in Asia and America suffer acutely at lower elevations (14–15,000 feet); and it would therefore seem that there are influences at work on the latter continents which do not operate in Europe. The apparent discordance is explicable without having recourse to local influences, which could not be deemed sufficient to account for the effects in general, even if they might be entertained in particular instances. Whilst the assumed causes are local, the observed effects are world-wide; and no cause would be adequate to account for the effects except one operating in every clime and at all times.

But, although it is very generally admitted that the evils which have been enumerated are due to diminished atmospheric pressure, many persons arc unconvinced that such is the true explanation, especially those who are accustomed to travel amongst the mountains of Europe; and it is pointed out, apparently with force, that the whole of the symptoms can be produced by other causes, and that aeronauts have sometimes attained higher elevations than have ever been reached on the earth, and have scarcely been affected at all. It is argued that some persons are predisposed to nausea,