ATMOSPHERIC PRESSURE AND LIFE-. 317 



(summit of Vesuvius), 56 centimetres at 2,432 metres (pass of the 

 Great St. Bernard), 46 at 3,998 metres (Mont Pelvoux), 39 at 5,920 

 metres (the height of the highest pass of the Himalaya is 5,835 metres). 

 The greatest height attained by man was reached by Glaisher in 

 a balloon 8,840 metres, pressure 24. 76 centimetres and by the 

 brothers Schlagintweit on foot, in the Himalaya, 6,882 metres, press- 

 ure 32 centimetres. The highest mountain on the globe, Gaurisankar, 

 measures precisely 8,840 metres the elevation at which Mr. Glaisher 

 fell fainting to the floor of his car. 



Such modifications of pressure cannot be endured with impunity 

 by the human organism. Though life in moderately elevated regions, 

 as the Jura and Auvergne, seems to be so beneficial to those who 

 dwell there constantly, that multitudes come thither from afar in 

 pursuit of health ; and though in regions situated at a greater alti- 

 tude, as the admirable plateau on which the city of Mexico stands, 

 the sum of the climatic conditions seems to oifer hygienic advantages : 

 still all are agreed that at very great elevations there always super- 

 vene, with more or less intensity according to persons and circum- 

 stances, certain characteristic perturbations and discomforts described 

 by travelers in the Alps, the Pyrenees, the Andes, and the Himalaya. 



These are, first, a sense of fatigue out of proportion to the amount 

 of walking or of work performed. The legs appear to become leaden, 

 and one feels a weakness in the knees. Then the breath becomes 

 short, diflicult, labored ; the pulse is quickened ; the heart-beats occur 

 isolatedly, and reverberate in the head. Next come singing in the 

 ears, dimness of sight, and vertigo. The general sense of malaise, 

 the feebleness, become such that the traveler must rest, else he will 

 fall to the ground. Simultaneously there occur other symptoms hav- 

 ing their seat in the digestive organs, such as nausea and vomiting. 

 Tiiese various symptoms, taken together, constitute mountain-sickness 

 {mal des montagnes) , which bears a resemblance to sea-sickness. 



When they first appear, a few moments' rest suftices to banish 

 them; this instantaneous restoration of strength and vigor sharply 

 distinguishes mountain-sickness from ordinary fatigue. But at greater 

 elevations, where graver symptoms appear, such as bleeding from the 

 nose or from the lungs, repose cannot bring back the condition of per- 

 fect health, though it always afibrds some relief. Travelers agree in 

 saying that a person on horseback suffers far less than one on foot. 

 On the high plains of the northern Himalaya, a rather brisk pace in 

 walking, the ascent of a hill however low, the carrying of a moderate- 

 ly heavy load, sufiice to exhaust one's strength, to cause him to faint, 

 and in some cases even to produce death. 



This is the reason why aeronauts are attacked much later than 

 those who ascend the mountain-side. Ever since the day when Mont- 

 golfier, realizing the immemorial aspirations of the human race, gave 

 to man the means of overcoming the gravity which ties him to the 



