696 Experiments 



Experiment CCLII. April 24. Under a bell of 2.5 liters, placed 

 on the plate of the pneumatic machine, and previously filled with 

 air very rich in oxygen, a sparrow is placed. Outside pressure 75 cm. 



The air then contains 82.2 per cent of oxygen; the pressure is 

 lowered. At 5:30, the pressure is only 13.5 cm.; the bird is uneasy 

 and flutters in the bell. At 9.5 cm., it is very sick and about to die. 

 Air somewhat superoxygenated is admitted. The bird recovers im- 

 mediately. 



5:38, the air contains 55.7 per cent of oxygen; we begin to lower 

 the pressure again, without being able to go lower than 11 cm. Air 

 somewhat superoxygenated is admitted; bird quite recovered. 



5:45, the analysis of the air has been lost. In the decompression 

 we reached only 13 cm. This time too, the bird is so sick that it re- 

 mains some seconds motionless on its back after normal pressure is 

 restored with ordinary air. 



5:55, the air contains only 22 per cent of oxygen; so that we 

 cannot pass below 18 cm. 



6:05, this time we use ordinary air; at 20.5 cm., the bird is very 

 sick; but he recovers perfectly under normal pressure. He has a 

 large bloody spot on his head. 



The oxygen tension at the moment when pressure had to be 

 restored was successively 10.7; 8.0; 5.0; 5.6. 

 This last experiment can be made still more simple. 



Experiment CCL1II. June 5. Green grosbeak (Fringilla chloris 

 Lin.). Put under the bell of the pneumatic machine. 



Pressure slowly decreased; sick at 30 cm. of actual pressure, and 

 as it stirred about somewhat, was quite sick at 22 cm. 



I then let pure nitrogen enter the bell to restore normal pressure. 

 The bird, far from recovering, dies almost immediately. 



It has in the cranial diploe a huge dark effusion. 



Whatever the operative procedure used, these different experi- 

 ments show clearly both the cause of the symptoms resulting from 

 decompression and the means of averting them. 



Evidently I could not limit myself to experiments made on 

 animals, however convincing, when I was issuing practical precepts 

 intended for mountain travellers and aeronauts. 



I resolved to begin by experimenting on myself. I had already 

 undergone, in my large sheet-iron cylinders, rather considerable 

 decompressions, to the point of experiencing certain discomforts. 

 I then thought of trying the test again, so as to remove the symp- 

 toms by breathing a superoxygenated air. 



I placed beside me in the apparatus a large rubber bag, con- 

 taining air whose oxygen content was in proportion to the degree 

 of decompression. Figure 56 shows the set-up of the experiments. 



I give here the details of three of them, and of a fourth which 



