540 Experiments 



The general conclusion from all this is that all disturbances, 

 symptoms, and death, which occur in consequence of diminution 

 of pressure, are due entirely to asphyxia; an animal subjected to an 

 increasing diminution of pressure is like an animal which smothers 

 in closed vessels in ordinary air, with the unimportant reservation, 

 as we shall see later, of the action of the carbonic acid produced. 

 When an animal in a closed vessel is subjected rapidly to a certain 

 decompression, and allowed to die, as in the preceding experiments, 

 the gradual depletion of the oxygen of the air in which it is con- 

 fined acts exactly as if one continued in a pure air to diminish the 

 barometric pressure around it. 



Oxygen tension is everything; barometric pressure in itself does 

 nothing or almost nothing. 



I shall stress these facts and the conclusions to be drawn from 

 them in another chapter, and I shall also indicate elsewhere the 

 practical results which may be deduced from them. 



I shall not now dwell upon the exterior phenomena displayed 

 by the sparrows subjected to the lowering of pressure. This study, 

 generalized and supported by precise observations made on animals 

 of different species, will be taken up in a special chapter. I shall 

 merely mention today three principal facts: 1, the increase in 

 number of respirations; 2, the drop in temperature; 3, the convul- 

 sions which precede death, and which will give us an opportunity 

 to judge the theory which attributes the convulsions to the action 

 of excess carbonic acid in the blood. 



I shall now give the results of experiments made on birds other 

 than sparrows. 



Experiments LII to LV, simultaneous. July 2. Temperature 20°; 

 pressure 76 cm. Owls (Stria; psilodactyla, Lin.) 



LII. Young, weighing 125 grams. Bell-jar of 2.25 liters. 



Entered at 3:07; left at normal pressure. 



Seemed affected at about 3:50, dies at 5 o'clock, with 3.8 cm. dim- 

 inution of pressure due to absorption. Dead after 1 hour 20 minutes 

 of distress. After 15 minutes, the rectal temperature is 31.3°; no 

 rigidity. 



Lethal air: O 3.3; CO 13.4. 



CO. 



CO. + O. = 16.7; 0.76. 



O; 



LIII. Like the foregoing. Bell-jar of 7 liters. 



Began at 3:15. At 3:20, pressure has been lowered 22 cm., some- 

 what uneasy. At 3:22, pressure has been lowered 41 cm., the bird is 

 calm; at 3:25, staggers; cocks closed. Actual pressure 27.7 cm. 



