Symptoms of Decompression 685 



C: all are dead too; but under the case of the chrysalis, meta- 

 morphosis is already far advanced. 



D: all dead, with a considerably lower degree of development. 



It would be interesting to make experiments with the eggs of 

 frogs, the larvae of insects, etc. 



6. Lower limit of pressure. 



The degree of decompression at which the different symptoms 

 I have just enumerated occur, that of the lower limit incompatible 

 with life, varies according to the species. The variation depends 

 also upon whether the animals remained calm or were restless 

 during the experiment. 



In sparrows, uneasiness generally begins to appear at about a 

 half -atmosphere. The bird becomes restless; it stops hopping about, 

 and its breathing becomes more rapid; about 25 cm. it begins to 

 vomit and waver on its feet; soon it falls, and if the decompression 

 approaches the fatal limit, it whirls about and jerks convulsively. 

 We saw above that this limit was ordinarily from 17 to 18 cm. 



It may vary, between rather narrow limits, for the same species, 

 in different animals, even when all the conditions of life appear 

 quite identical. Here is an experiment in proof. 



Experiment CCXLVIII. June 18. 4 sparrows: A, old, vigorous 

 male; B, C, D, females, in good health; all together in the same cage 

 for several days. Placed together in a large bell of 30 liters, under a 

 current of air. A cloth covering the bell keeps them from being 

 frightened and stirring about unequally; they remain very calm dur- 

 ing all the first part of the experiment, that is, until they are affected 

 by the rarefied air. 



Decompression begins at 4:45. 



At 4:49, pressure is only 38.8 cm.; B and D vomit repeatedly. 



At 4:52, pressure 29.8 cm.; A also vomits. 



At 4:53, pressure 27.8 cm.; C vomits; D is very sick. 



At 4:54, pressure 26.8 cm.; all panting and crouched down, except 



C, which is standing on its feet. 



At 4:55, pressure 24.8 cm.; all are walking, dragging themselves 

 this way and that, except that A remains motionless, its beak on the 

 floor. 



At 4:56, pressure 23.8 cm.; A is evidently the sickest; then come 



D, then B, and finally C, considerably better than the others. 



At 4:58, pressure 21.3 cm.; A and D seem dying; they have fallen 

 over, panting and in convulsions. 



At 4:59, pressure 20.3 cm., then the cocks are opened wide; A and 

 D remain for some time on their backs, and do not recover until 

 after the others. 



At 5:30, all are well. 



They survive. 



