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THE POPULAR SCIENCE MONTHLY. 



life of the bird is plainly not at all endangered. If I were to admit 

 oxygen once again, I might diminish the pressure still more. 



Hence it appears that it is not the lowering of mechanical pressure 

 that produces the symptoms, but the low tension of the oxygen of the 



Fig. 1. 



dilated air, which low tension prevents the oxygen from entering the 

 blood in sufficient quantity. 



This experiment I have made not only with sparrows, but also on 

 my own person ; and in the latter case the results are quite as strik- 

 ing as in the former, and I dare affirm, without vanity, no less inter- 

 esting. 



By the kindness and liberality of Dr. Jourdanet, I have been en- 

 abled to set up in the jDhysiological laboratory of the Sorbonne great 

 apparatus, by the aid of which I have studied the effects of compressed 

 and dilated air. The dilated air-chamber consists of two cylinders of 

 riveted sheet-iron, from which the air is gradually exhausted by means 

 of a steam-pump (Fig. 2). 



This apparatus I have entered, taking with me a large India-rubber 

 bag filled with oxygen. As the pump began to work, I experienced 

 all the well-known symptoms of mountain-sickness, viz., quickening of 

 respiration and pulse, which was considerably augmented by the least 

 movement ; sense of loathing, nausea, sensorial and intellectual pertur- 

 bation. I felt indifferent to everything and incapable of action. On 

 one occasion, having counted my pulse-beats for one-third of a minute, 

 I tried to multiply the number of beats by three, but could not do it, 

 and so was obliged to write on my bit of paper, " It is too difficult." 



