986 Summary and Conclusions 



sider an individual whose arterial blood contains 20 volumes of 

 oxygen, per 100 volumes, and whose venous blood contains 12, 

 an individual who consequently for the needs of his organic com- 

 bustions consumes 8 volumes. of oxygen borrowed from his ar- 

 terial blood. Let us now suppose him subjected in a balloon to 

 the effect of diminished pressure. The oxygen of his arterial blood 

 will decrease progressively as we have seen, and naturally the same 

 thing will be true of his venous blood. But he will pass through 

 two successive phases which we should study carefully. In the 

 first, the impoverished arterial blood, in spite of the compensa- 

 tory efforts attempted by the respiratory apparatus, will drop to 

 18, 16, 14 volumes of oxygen; that is when — if we take as a basis 

 of our calculations the graph of Figure 31 — the pressure has been 

 lowered to 62, 48, 40 cm., corresponding approximately to elevations 

 of 1600, 3600, 5100 meters. If there is no change in the intensity 

 of his intra-organic combustions, our aeronaut will still need the 8 

 volumes of oxygen which he consumed at normal pressure, and his 

 venous blood will contain 10, 8, 6 volumes of oxygen. These figures 

 represent degrees of saturation of the hemoglobin which are easily 

 dissociated for the needs of organic combustions; the quantity of 

 oxygen necessary for the inner phenomena of metabolism will have 

 been found, and nothing will be changed in the general equilibrium 

 of our aeronaut. Of course, his tissues will be bathed in a blood 

 relatively low in oxygen; but as they can extract from it what they 

 need, although with a little more difficulty than in the normal state, 

 nutritional disturbances with their functional consequences will be 

 only slight. 



But the balloon is still rising and reaches successively 5700 

 meters (37 cm.) , 6600 meters (33 cm.) , 8600 meters (26 cm.) ; the 

 oxygen of the arterial blood drops to 13, 12, 10 volumes. Then it 

 becomes more and more difficult to find the 8 volumes of oxygen 

 necessary for the regular maintenance of the organism, for the 

 venous blood must fall to 5, 4, 2 volumes, and the oxy-hemoglobin 

 shows itself more and more rebellious to reduction. In fact, ex- 

 perimentation has shown that this reduction does not take place; 

 the graphs of Figure 40 are very characteristic and show that the 

 oxygen consumption lessens in the organism, the difference dimin- 

 ishing between the graphs, till then parallel, which represent the 

 oxygen content of the arterial blood and that of the venous blood 

 at different pressures. Then, simultaneously, we see diminishing 

 in growing proportion the quantity of oxygen consumed from the 

 air, the carbonic acid expelled, and the urea excreted; then too the 



