AIR AND LIFE. 185 



projected lift to fear the effects of altitude. The example of the inac- 

 tive guinea pig assures them of immunity, and except in some almost 

 impossible cases of anaemia or weakness they will experience no dis- 

 comfort. On the other hand, incipient alpinists must perceive that 

 the advice commonly given by guides has a solid foundation. The 

 example of the active guinea pig shows them that ascensions must 

 be performed slowly, without haste, without great exertion, without 

 getting out of breath. To be out of breath means incipient asphyxia, 

 and asphyxia means mountain sickness. So the excursionist must 

 learn to climb slowly, with careful and measured step. 



In brief, high altitudes must unavoidably bring on asphyxia and 

 mountain sickness, but at moderate altitudes both are avoidable by 

 reducing the exertion; they may be brought on by increasing one's 

 efforts, and it is only by assuming the nearly perfect immobility of the 

 aeronaut that one can hope to attain without discomfort the highest 

 altitudes, since it is during such immobility that the organism needs 

 least air. 



Having considered the case where an animal or man passes gradu- 

 ally from a low to a high level, we must now turn to another, that in 

 which the change is sudden or extremely rapid. This is not exceptional, 

 but does not occur in the course of mountain climbing, for obvious 

 reasons; and in the case of balloon ascents, where it would seem to 

 be of common occurrence, we rarely hear of any serious inconvenience 

 experienced, although the balloon often seems to rise very rapidly. 

 The truth is that it rises rapidly to a moderate altitude only, and 

 that it gets into really high altitudes only after a lapse of time quite 

 sufficient for adaptation. To encounter cases of rapid decrease of 

 pressure, we must turn in another direction, and we find examples 

 where men work under high pressure, for instance, in diving bells, 

 under the surface of the sea or of a river, to explore a wreck or build 

 the foundations of a pier or bridge. Here, in order to counteract the 

 great pressure overhead, that of the water added to the normal sea- 

 level pressure — and every ten meters in depth of water adds the pres- 

 sure of one atmosphere — air must be forced into the bell or diving appa- 

 ratus, and the men are subjected to a total pressure amounting to three 

 or four atmospheres. As it sometimes accidentally happens that the 

 passage from this high pressure to the normal air is very rapid, the study 

 of the results is instructive for the present purpose. These are often 

 most unfavorable and death not uncommonly ensues. The same occurs 

 when an animal in a bell jar is rapidly subjected to a decrease of pres- 

 sure, or when, in a bell jar, where an animal has been placed and the 

 pressure gradually increased by forcing air into it, the pressure is sud- 

 denly decreased merely by allowing the air to escape into the atmos- 

 phere. In both cases, and in fact in all cases where the passage from 

 relatively high to comparatively low pressure is rapid or quite sudden, 

 symptoms arise which are generally fatal. The animal falls on its side 



