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
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 striking as in the former, and I dare affirm, without vanity, no less interesting.
By the kindness and liberality of Dr. Jourdanet, I have been enabled to set up in the physiological 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 perturbation. 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."