866 INFLUENCE OF A RAREFIED ATMOSPHERE 



pulse, paleness or blueness of the skin, languor 

 and prostration of strength, dimness of sight, and 

 general loss of sensibility, nausea, giddiness, and 

 symptoms of apoplexy, as observed by De Saus- 

 sure when near the summit of Mont Blanc. The 

 same effects are produced in a still more remark- 

 able manner, on the high mountains of India and 

 South America, where the amount of respiration 

 is so far diminished, that the blood is chilled to 

 the very centre of the system. It is well known 

 that in the polar regions, life may be sustained 

 for many hours with suitable clothing, when the 

 temperature is from 30 to 50 below 0. But Dr. 

 Gerard states, that many lives are lost in crossing 

 the Himalayas, when the temperature is 16 F., 

 at the height of 14,000 feet, owing to the united 

 influence of rarefaction, external cold, and ex- 

 haustion from exertion. He says that in crossing 

 the Manerung, at an elevation of 18,612 feet, 

 respiration was hurried and difficult, long before 

 reaching the summit that the least motion was 

 attended with mental dejection and debility, 

 which compelled him to sit down every few 

 yards. 



And it has been observed on the high moun- 

 tains of South America, that symptoms are pro- 

 duced analogous to those arising from excessive 

 loss of blood that when mules are attacked with 

 hurried breathing and trembling of the limbs, 

 they stop short, or attempt to lie down but that 

 if compelled to go on, they often fall prostrate, 



