THE AIR AND LIFE. 537 



And further: " I ain inclined to believe that the air in that region is 

 so subtle and delicate that it is not adapted for hunur.i breathing which 

 requires it to be coarser and more temperate." The correctness of 

 these last words, uttered three hundred years before the time of 

 Priestley and Lavoisier, is striking. The air at high elevations is 

 indeed too rare, too subtle for superior beings to breathe. The dis- 

 temper described by Acosta is that which, in different localities, is called 

 puna^ soroche, veta, mountain or balloon sickness. More recent descrip- 

 tions of it have been given by Tschudi, Lortet, and many others; all 

 have observed the dizziness, the vomiting, the anxiety, the fainting by 

 which it is characterized. Certain experiments by Lortet and by Chau- 

 veau and others have shown that respiration is abated and at the same 

 time quickened. There have been noted intense muscular pain, and 

 circulatory and nervous disorders which end in paralysis and death, if, 

 as happened in the disaster of the " Zenith," these disorders occur 

 sinuiltaneously for some time. 



Without describing the opinions held at various times in regard to 

 the cause of these dreadful accidents, we shall confine ourselves to 

 recalling the explanation recently given by Paul Bert and other physi- 

 ologists. It is a very sim])le one; the deadly disorders are brought 

 about by a diminution of the tension of oxygen, the diminution grow- 

 ing out of the relative rarefaction of that gas, the air being more rari- 

 tied, more <lilated, as it were, in elevated than in intermediate regions. 

 In truth, Paul Bert's researclies show that in these cases the diminution 

 of pressure kills organisms not by its mechanical effect, but by a chem- 

 ical effect, by the scarcity of oxygen, by producing inioxi/hetuia, or 

 deficiency of oxygen in the blood. An animal immersed in a raritied 

 atmosphere dies from the same cause as an animal breathing in a close 

 non- ventilated space; both die for lack of oxygen. In the case of fish 

 living in great <le})ths, when they come too near the surface the gases 

 which exists in their bodies in a state of powerful tension easily burst 

 the tissues asunder as soon as the exterior pressure becomes notably 

 less than the interior. This same thing sometimes happens to man, as 

 we shall see presently. 



The case we have just examined is that of anaiiimal, or man, passing 

 gradually from a low or intermediate level to a very high one. We have 

 now to consider another case, that in which the transition from a 

 normal or high pressure to a low one takes place suddenly. Instances 

 of this occur when a man working under a i^ressure of 3 or 4 atmos- 

 pheres in the caisson of a bridge pier suddenly returns to the surface ; or 

 when a diver is too hasty in coming out of the water, or when an an'onaut 

 is accidentally lifted to high elevations by a balloon overcharged with 

 gas. In cases Avhen pressure is rapidly diminished death is known to 

 supervene in a very short time. An animal placed in a bell glass in 

 Avhich the pressure, normal at first, is suddenly lowered by means of a 

 few strokes of the air-pumj), will be prostrated and die forthwith, 

 although the final pressure may not be at all incompatible with life, if 



