Theories and Experiments 243 



sickness attacks not only travellers on foot, but also horsemen; why 

 the former are stricken much more severely (twice as severely, ac- 

 cording to Tschudi); why exertion aggravates it; why it disappears 

 when the traveller stops walking for a moment and reappears imme- 

 diately when he starts again; why, however, just as horsemen 

 themselves feel its painful symptoms, so at very great heights rest 

 does not completely free travellers from it (de Saussure, A. Vogt) ; 

 why walking on a level at great heights is often accompanied by 

 distress which increases when one walks more quickly or begins to 

 climb; why aeronauts are not exempt from disturbances of respiration 

 and circulation; why patients stricken by the disease of the Puna are 

 advised to sit quietly in rooms which are warm and well closed, etc. 

 (Pages 131-133.) .... 



Other phenomena can in part be attributed to the immediate 

 action of the diminished pressure, as, for example, the strange sensa- 

 tion of lightness of which many travellers speak, the violent beating 

 of the heart, qualms, nausea, vomiting, and oppression. In fact, the 

 lessened pressure of the air, by lowering resistances, aids rapid walk- 

 ing, respiratory movements, and the action of the heart, while at the 

 same time it tends to increase the volume of gases contained in the 

 intestinal canal; so that distention of the stomach and the crowding 

 upward of the diaphragm may bring on nausea and oppression. But 

 these phenomena of direct action may be relegated to the second 

 rank, as I have already said. (P. 134.) 



We know, from the experiments of the Webers, that the great 

 lassitude of mountain travellers is due to a direct action of the 

 diminished atmospheric pressure; but we must understand that not 

 only the large muscles, those that move the large bones and hold 

 them in their articulations, become weary, but the same thing is also 

 true of the small muscles, like those of the tongue and the larynx 

 (Parrot and Hamel) ; a phenomenon which must be general and keep 

 increasing, as A. Vogt asserts, if it is the consequence of the decrease 

 in pressure, and that really does happen. Here too, we must make 

 allowance for individual peculiarities. (P. 135.) 



So, in the eyes of Meyer-Ahrens, the immediate causes of 

 mountain sickness are, in the first place, the decrease in the abso- 

 lute quantity of oxygen in the rarefied air; then come the rapidity 

 of evaporation, the intense action of the light, the increase in vol- 

 ume of the intestinal gases, and a weakening of the coxo-femoral 

 articulation. 



Dr. Lombard, TS who almost at the same time wrote for the 

 Bibliotheque de Geneve excellent articles which he soon afterwards 

 collected and published in a brochure, returns purely and simply 

 to the two old explanations of de Saussure: diminution of weight 

 sustained, diminution of the quantity of oxygen contained in the 

 same volume of air; then the theory of the Webers appears again: 



