Decreased Pressure 987 



temperature begins to drop. Then, consequently, there appear, 

 with an equally growing intensity, serious physiological disturb- 

 ances, due to the insufficiency of the quantity of vital force set at 

 liberty; the respiratory muscles, the heart, which till then had 

 struggled to. carry on the metabolism, fall exhausted, so to speak; 

 the whole muscular system, the venous system, which can hardly 

 find in the impoverished blood the oxygen strictly necessary for 

 their static maintenance, can carry on no energetic or lasting work. 

 And, by the usual series of sympathies, of organic harmonies, that 

 which was effect becomes cause in its turn: the chilled tissues 

 become less fitted for combustion: the sluggish and weakened heart 

 no longer pumps the nourishing liquid with the same abundance, 

 and the unhappy aeronaut, dragged on in this sort of vicious spiral, 

 rapidly descends the slope which leads to death. 



So, in summary, two phases: phase of struggle, phase of defeat, 

 with a passage from one to the other whose duration will vary 

 according to many circumstances, which we shall rapidly review. 

 We can divide them into two classes: some are inherent, others out- 

 side the person under observation. 



Among the inherent circumstances, we have already mentioned 

 as favorable the abundant blood supply of the organism, the large 

 oxygen content of the blood, the great capacity of the blood for 

 oxygen, and the smallest relative consumption of oxygen in the 

 blood as it passes through the tissues. There are others also, and 

 important ones, which we do not understand as clearly at first, 

 and which depend on the chemical state of the tissues themselves. 

 Another possibility is, when the quantity of oxygen brought is 

 very small, a tissue in which rest has permitted an accumulation 

 of materials that are easily oxidizable, or a tissue drained of these 

 materials by previous functioning that was too energetic. In the 

 first, everything will be ready for a maximum utilization of the 

 oxygen brought, and consequently for a maximum output of vital 

 force; in the second, on the contrary, beside the phenomena of 

 discharge of vital force and of combustion, the organic equilibrium, 

 lowered to its very limit, will require reductions, the storing up of 

 vital force which will lessen by so much the total available for 

 outlay in heat and work. In addition, the digestion, which gives 

 the organism materials easy to oxidize, must establish a condition 

 favorable to the preservation of a state compatible with strength 

 and health. Finally, to end what pertains to the inherent cir- 

 cumstances, we shall mention the disastrous effects of muscular 

 or intellectual efforts, which, requiring for their accomplishment 



