686 Experiments 



I have shown that it is possible, with suitable precautions, to 

 reach 10 cm. (Exp. XXXIX) , a limit which agrees with that indi- 

 cated by the calculation for the minimal pressure of oxygen. This 

 limit must be reached very slowly. On the other hand, if the drop 

 is sudden, the symptoms appear much sooner, and for example, 

 death occurs suddenly between 25 and 30 cm. The same thing is 

 true when the animal struggles. 



Inversely, it often happens that an animal which appears very 

 uneasy, near death, under a very low pressure, recovers, gets up, 

 and becomes fairly well accustomed to it. 



All these data, which complicate the numerical solution of the 

 problem, agree perfectly with the observations of mountain travel- 

 lers and with what we know of the conditions of asphyxia. 



The more carefully the transitions are managed, the more easily 

 the experimental animals become accustomed to them; the greater 

 the consumption of oxygen, the more quickly the effect of its lack 

 will be noted. Travellers, like birds under decompression, like 

 asphyxiated animals, in a general way, suffer more in proportion to 

 their activity; we have had many examples of travellers being 

 forced at certain heights to stop in order to become accustomed to 

 conditions, and to lie down in order to lessen the consumption of 

 oxygen. The data I have given agree with this perfectly. 



Add that, after a certain number of experiments, summarized 

 in Table II, the resistance is considerably less when the tempera- 

 ture is very low. This is an important consideration, for travellers, 

 like aeronauts, are generally exposed to this depressing condition. 

 Now nothing is more natural than that the consumption of oxygen 

 should be increased by the cold, if the temperature of the body is 

 not to be considerably lowered. 



Different species. If we consider the average resistance pre- 

 sented by the different species, we find that in birds, birds of prey 

 appear almost as sensitive to decompression as sparrows. This is a 

 strange fact, when we consider the considerable atmospheric 

 heights reached by the large birds of prey. 



The following experiment, if we compare it with the preceding 

 one, made the same day, gives a clearer proof than those taken 

 from Table IV. 



Experiment CCXLIX. June 18. Gull (Larus ridibundus Lin.) 

 and hawk (Falco tinnunculus Lin.). 



Decompression was made in the same conditions of speed as for 

 the sparrows in Experiment CCXLVIII. I summarize in the follow- 

 ing table the phenomena presented by the three species under the 

 same pressure. 



