340 Historical 



observations are evidently tainted with causes of error which 

 vitiate them as sources of proof: even the experiments of Legallois 

 (page 218) , notable as they are, cannot be used in his favor, since 

 they deal with confined air. 



The theory of M. Dufour (page 291) is also independent of the 

 idea of altitude. In his opinion, mountain sickness is the conse- 

 quence pure and simple of fatigue, which results from the 

 exhaustion of the ternary materials stored in the muscles; and so 

 he states that he experienced the symptoms even on the plain, 

 after great fatigue. It cannot be merely the rarefaction of the air, 

 he says, which makes one ill on the summit of Mont Blanc, be- 

 cause aeronauts had to reach 7000 and 8000 meters to experience 

 serious disturbances; moreover, these disturbances do not at all 

 resemble those produced on the mountain. 



We leave to the reader the task of weighing the value of this 

 last statement, and as for the comparison of mountain sickness to 

 simple fatigue, we shall merely ask why it has never been made 

 by tourists, who, not without great fatigue, walk all day in 

 mountains less than 2000 meters high. At least they have never 

 confused the lasting weariness which they experience in the eve- 

 ning with the sudden "blow on the knees" which exhausts the limbs 

 and disappears after a few minutes rest; nor have they confused 

 the breathlessness and the acceleration of the pulse due to a la- 

 borious or rapid walk with the dyspnea, the palpitations, and the 

 total exhaustion which, at an elevation of 4000 meters, often halts 

 the traveller after a few steps. There is, therefore, something be- 

 sides the exhaustion of the ternary materials, and this something 

 is the altitude reached, or, to speak more clearly, the diminished 

 pressure. This objection is evidently applied to the ideas of Bou- 

 guer, Lepileur, and Lortet, as well as to the theory of Dufour. 



We now come to the theories which involve the decrease in at- 

 mospheric pressure. Laboratory experiments had shown that ani- 

 mals placed under the bell of the pneumatic machine became ill, 

 even died, when the pressure was lowered sufficiently, and the con- 

 clusion had been drawn that the lowered air pressure on lofty 

 mountains was probably the chief cause of the symptoms. But 

 how does it act? Here the theories become numerous. 



Decrease of the iveight sustained by the body. One of the first 

 which entered the minds of travellers may be summarized thus: 

 At normal pressure, each square centimeter of our bodies sustains 

 a weight of 1.03 kilograms, or, for the entire surface, a number 

 which should be 18,000 kilograms for a man of average height. 

 We do not feel this enormous weight which would crush us, the 



