Summary and Discussion 343 



monary and general capillaries, the walls of which, since they are 

 thin and lack resistance, may be ruptured. Such is the mechanism 

 of the production of hemorrhages." 



Indeed it seems settled, in spite of the objections of Ch. Darwin 

 (page 207), John Davy (page 224), and M. Giraud-Teulon (page 

 246), that at a sufficiently low pressure, gases escape from the 

 blood of living animals placed under the pneumatic bell; F. Hoppe 

 did not even hesitate to conclude that the death of the animals 

 under these conditions is due to this release of gases. But noth- 

 ing in the experiments yet known proves that the escape takes 

 place at pressures which coincide with mountain sickness, nor that 

 the tendency to escape can bring on the disturbances for which it 

 is blamed. No comparison can be made between an animal brought 

 in a few minutes to a fatal decompression and a traveller who 

 takes six hours to ascend vertically 2000 meters. If the gases were 

 partial cause of the symptoms, aeronauts, who undergo enormous 

 changes in pressure with great rapidity, would be the first to be 

 stricken, and we know that that is not the case. 



Expansion of intestinal gases. The idea that the decrease of 

 pressure must expand the intestinal gases is evidently not wrong 

 from the standpoint of physics; but that is far from justifying the 

 conclusion that this increase in volume is the cause or one of the 

 causes of mountain sickness. However, Clissold (page 224) con- 

 sidered that it must hamper respiration and circulation consider- 

 ably. M. Lepileur (page 237) and Speer (page 241) also tend to 

 attribute some effect to it; M. Maissiat is more positive: "The in- 

 testinal gases, gaining volume, distend all, to the point of rupture" 

 (page 234) . The learned physicist reasoned as if the intestine was 

 a closed swimming bladder, and he forgot the double communica- 

 tion with the exterior, which, in practice, permits no distention. 

 The same thing is true of M. Colin, who sees a cause of death in 

 "the forcing back of the diaphragm by the expansion of the gas" 

 (page 307) . 



Loosening of the coxo-femoral articulation. It is under the 

 patronage of the illustrious von Humboldt (page 228) that there 

 appeared this odd explanation of the extreme fatigue and the 

 heaviness of the lower limbs which appear in lofty ascents. It 

 has since been accepted by many writers: Tschudi (page 232), 

 Meyer-Ahrens (page 243), Lombard (page 252), and Guilbert 

 (page 255) . 



It is undeniable, as B6rard (page 312) has shown, that the sur- 

 face of the cotyloid cavity is sufficient to permit the atmospheric 

 pressure to support the weight of the leg, when all the soft parts 



