6 Historical 



more recently, officers, scholars, and English travelers have carried 

 their explorations into the loftiest regions of the Himalayas. Their 

 accounts, added to those of men who have ascended the Alps and 

 of travellers in America, which have become more numerous, have 

 familiarized physicians with the symptoms of mountain sickness. 



In the following pages I shall report most of the interesting facts 

 collected thus by eyewitnesses, often from their own personal ob- 

 servation. But in this preliminary chapter I should like to recall 

 to the memory of the reader the different mountain regions in 

 which the traveller is exposed to distress in consequence of the 

 decrease of pressure. This simple enumeration will show him the 

 practical importance of the question which we shall discuss here, 

 that is, the manifestation by acute and violent symptoms of the 

 effect of decreased pressure. 



Rarely does mountain sickness appear with marked intensity in 

 our temperate regions below an altitude of 3,500 meters. In the 

 tropics, one must mount to more than 4,000 meters to experience 

 it definitely in ordinary conditions. We shall return to these limits 

 and take account of the different circumstances which hasten or 

 delay the symptoms, I mean by that, cause them to appear at a 

 lower or higher altitude. For the moment, these approximate 

 heights serve as a basis for the review we intend to make. 



Europe. Let us take Europe first; the Alps, the Pyrenees, and 

 the Caucasus are almost the only mountain chains which offer us 

 peaks high enough for their ascent to cause any other ill conse- 

 quences than the weariness and the dangers customary in moun- 

 tains. 



Let us first examine the Alps. This enormous mass of moun- 

 tains which includes in a curved line two hundred leagues long 

 innumerable peaks laden with eternal snows, descends rapidly on 

 the south to the low plains of Lombardy, while on the north it 

 slopes more slowly towards the high plateaux of Wurtemberg, 

 Bavaria, and Bohemia, interrupted by secondary mountains. 



The heart of the system is formed by the group of Saint-Gothard, 

 whose waters flow at the same time through the Rhine into the 

 North Sea, through the Rhone into the Mediterranean, and through 

 the Tessin into the Adriatic; and yet this region is one of the least 

 elevated of the Central Alps. It is immediately dominated on the 

 north by Galenstock (3800 meters) and Todi (3600 meters); on 

 the east, by the group surrounding the Little Saint-Bernard, among 

 others the Rheinwaldhorn (3400 meters) ; on the west, by the 

 enormous mass of the glaciers of the Bernese Alps, in the midst of 



