Now from the estimations in the last section, it appears that 63 cubic inches of oxygene are consumed, and about 52 cubic inches of carbonic acid produced every two minutes during the natural respiration of common air. So that supposing the experiment accurate, 6 cubic inches of oxygene less are absorbed, and 30 cubic inches less of carbonic acid produced every minute, when oxygene nearly pure is respired, than when atmospheric air is respired. Both these experiments were made in the morning, at a time when I was in perfect health; so that there could be apparently no source of error from accidental circumstances. The uncommon and unexpected nature of the results, made me however, very sceptical concerning them; and before I would draw any inferences, I resolved to ascertain the comparative consumption of atmospheric air and oxygene by the smaller quadrupeds, for which purpose, I made the following experiment. E. 3. Of two strong and healthy small mice, apparently of the same breed, and exactly similar. One was introduced into a jar containing 10 cubic inches and half of oxygene, and 3 cubic inches of nitrogene, and made to rest on a bit of cheese. The other was introduced into a jar containing fifteen cubic inches and half of atmospheric air, and made to rest in the same manner on cheese. The mouse in oxygene began apparently to suffer in about half an hour, and occasionally panted very much; in about an hour he lay down on his side as if dying. The jars were often agitated, that the gases might be well mingled. The mouse in atmospheric air became very feeble in 40 minutes, and at the end of 50 minutes was taken out through the mercury alive, but unable to stand. The mouse in oxygene was taken out in the same manner after an hour and quarter, alive, but motionless, and breathing very deeply. The gas in the jars was examined. That in the oxygene jar filled a space exactly equal to 12,7 cubic inches, and analised, was found to consist of 1,7 carbonic acid, 2,6 of nitrogene, and 8,4 of oxygene. So that absolutely, 2,1 cubic inches of oxygene and,4 of nitrogene had been consumed, and 1,7 of carbonic acid produced. The gas in the atmospheric air jar was diminished nearly to 14,4, and consisted of 2,1 carbonic acid, 1,4 oxygene; and 10,9 nitrogene. So that 2,7 of oxygene and,5 of nitrogene, had been consumed by the mouse; and 2,1 of carbonic acid produced. Hence it appears, that the mouse in atmospheric air consumed nearly one third more oxygene and produced nearly one fourth more carbonic acid in respiration in 55 minutes, than the other in an hour and quarter in oxygene. And if we consider the perpetual diminution of the oxygene of the atmospheric air; from which at last it became almost incapable of supporting the life of the animal; we may conclude, that the quantity of oxygene consumed by it, had the air been perpetually renovated, would have been much more considerable.