Decreased Pressure 989 



Sivel, and Tissandier in two hours reached the height of 8600 

 meters, the decrease in pressure being about three quarters of an 

 atmosphere. Now we have seen that even the slightest symptoms 

 of sudden decompression never appear for an almost instantaneous 

 decompression from one atmosphere; beyond, for decompressions 

 from several atmospheres, twenty minutes per atmosphere give 

 protection from symptoms; we are far from the conditions pre- 

 sented by aeronauts. 



We now understand perfectly the phenomena the aeronaut will 

 present as he rises in his balloon. At lower heights, a slight ac- 

 celeration of the pulse and the respiration attempting to compen- 

 sate for the diminution of oxygen which the blood begins to un- 

 dergo, an acceleration which seems to have some of the con- 

 sequences of fever, as it has some of its symptoms. At this time, in 

 fact, observers have noted a certain intellectual excitement, with 

 a feeling of well-being, of lightness, of strength, which I do not 

 think should be ascribed solely to the excitement of the trip, or 

 to the splendid spectacles offered to the admiration of the aeronaut 

 by the clouds lighted from above by the sun. I think that the 

 increased activity of the circulation, subjecting the organs and par- 

 ticularly the nervous centers to a more rapid irrigation, takes from 

 them more completely the waste products of metabolism and by 

 this sort of washing puts them in conditions most favorable for 

 their functioning. On the other hand, not only the carbonic acid, 

 but all the gaseous impurities which our blood absorbs at ground 

 level, particularly in the air of large cities, escape in an already 

 considerable proportion, and our organs, so sensitive to the influ- 

 ence of these noxious matters still mostly unknown, must ex- 

 perience advantages easier to divine than to define precisely. 



But the balloon continues its upward course: it reaches and 

 passes 5000 meters. The oxygen diminishes in the blood in con- 

 siderable proportion, although enough is left for the necessary 

 consumption. The enthusiasm, the feverish excitement ex- 

 perienced about 2000 meters have nearly disappeared; the heart 

 beats rapidly; movements become rather painful, the cold is felt. 

 Higher yet, rest becomes indispensable; the impoverished blood, 

 can no longer provide the increase of oxygen required for muscular 

 contractions; so the least effort causes panting, palpitations; the 

 sturdy Sivel can hardly lift a bag of sand weighing 20 pounds to 

 the level of the basket; drowsiness overcomes the passengers; they 

 have vertigo, buzzing in the ears, dizziness; the sky appears almost 

 black, partly because of the weakness of vision. Finally, higher 



