MOUNTAIN SICKNESS. 95 



the four individuals concerned were beating very rapidly 

 indeed — more than was the case with the same persons 

 when .hey had climbed 8000-9000 feet higher. From 

 this I conclude that fatigue or excitement, or both, rather 

 than the rarefaction of the atmosphere is the cause of the 

 quick pulse rate which has been associated with mountain 

 sickness. Figs. 4-12 show that at heights of 17,000-23,000 

 feet the heart-beat need not be greatly quickened. 



Fig. 3, showing tracings taken at 16,000 feet, reveals 

 nothing abnormal in the form of the pulse curves. Fig. 4, 

 at 17,000 feet, shows curves which one may get any day 

 at sea-level. 



Fig- 5' at ' 8,000 feet, cannot be called at all unusual. 

 Fig. 6, at the same height, may be called a good healthy 

 pulse. Fig. 7 is more dicrotic than is usual, but is not 

 abnormal. Fig. 8, at 20,000 feet, with a fall to 48 heart- 

 beats per minute, shows vagus action, the ventricles 

 missing every alternate beat of the weakened auricular 

 contractions. It is one form of the pulse of a distressed 

 heart and the form of the wave corresponds. Fig. 9, in 

 Conway's case, looks like an anacrotic pulse wave, which 

 is generally, but not always, associated with high arterial 

 pressure ; but in any case Zurbriggen's tracing at the same 

 height is not one of high pressure. Figs. 1 1 and 12 are of 

 not unusual form, and the rate of heart-beat is slowed down 

 to about the normal in unfatigued individuals. 



It may be said at once that these tracings do not enable 

 us to decide the question as to whether heart-failure is or 

 is not an essential element in mountain sickness. Two of 

 them show unmistakably increased vagus action on the 

 heart, but the others show rather evidence of fatigue than 

 anything else. The vagus action is a sign of a distressed 

 heart, and is usually if not always present in heart-failure, 

 but it is often enough brought into play long before the 

 heart has become overstrained. The palpitation of the 

 heart which is so commonly noted in mountain sickness 

 and exertions is, as we have pointed out, another sign ol 

 a distressed heart. It must be remembered that the 

 tracings were taken during periods of rest, when the rare- 



