984 Summary and Conclusions 



and without convulsions, if the diminution of pressure has not 

 been brought too suddenly to its fatal degree. 



The symptoms of decompression disappear very quickly when 

 the balloon descends from the higher altitudes; very quickly also, 

 as I have often seen in my experiments, the normal proportion of 

 oxygen reappears in the blood. There is an unfailing connection 

 here. 



No less striking is the correlation between the data observed in 

 balloon ascensions and those in the only two known cases in which 

 men have been subjected to air with low oxygen content, without 

 the interference of carbonic acid. The first was observed, as I 

 have already said, by M. F. Leblanc in the pyrites mines of Huel- 

 goat in Brittany. In a gallery in which the air contained only 9.8% 

 of oxygen, and which he entered without transition, he had at- 

 tacks of vertigo and fainting. Now that oxygen tension nearly 

 corresponds to that of the air at a height of 6000 meters, where 

 certainly balloon sickness would violently attack anyone who ex- 

 posed himself to it suddenly. The second, observed by M. Forel, 

 is particularly noteworthy because of the similarity of the mental 

 symptoms which he experienced in air with a low oxygen content 

 and those from which I myself suffered under a decompression 

 corresponding to the height of Mont Blanc. 



The moment at which aeronauts feel and the experimental ani- 

 mals manifest serious disturbances varies, as we have seen, not 

 only with the species, but with individuals in the same species. 



The analysis of the gases of arterial blood shows us inequalities 

 quite of the same order, which certainly are the immediate cause 

 of these differences. At a pressure of 36 cm., one of my dogs (Ex- 

 periment CLXXI, number 10 of Table X) had lost 55.6% of the 

 oxygen of his blood, another (Experiment CLXXIV, number 11) 

 having lost only 36.1 (Table X, column 14) ; they had, however, 

 reached about the same figure (8.5 and 8.9, column 8). Another 

 of my dogs showed (Experiment CLXX, numbers 2 and 5) a very 

 remarkable resistance: at 56 cm. he lost only 3.2% of his oxygen; 

 at 46 cm., only 5.5, keeping the high proportion of 20.3. 



A careful inspection of Table X shows many interesting in- 

 equalities in this point; but we cannot find the reasons for these 

 inequalities. Neither the vigor of the animals nor the original 

 oxygen content of their blood can serve in themselves as an ex- 

 planation. Nevertheless, by considering the general results of the 

 analyses of the blood gases, one can account fairly well for these 

 phenomena. 



