a. Of two middle sized water-lizards, one was introduced into a small jar filled with nitrous oxide, over moist mercury, by being passed through the mercury; the other was made to breathe hydrogene, by being carried into it in the same manner.
The lizard in nitrous oxide, in two or three minutes, began to make violent motions, appeared very uneasy, and rolled about the jar in every direction, sometimes attempting to climb to the top of it. The animal in hydrogene was all this time very quiet, and crawled about the vessel without being apparently much affected. At the end of twelve minutes, the lizard in nitrous oxide was lying on his back seemingly dead; but on agitating the jar he moved a little; at the end of fifteen minutes he did not move on agitation, and his paws were resting on his belly. He was now taken out stiff and apparently lifeless, but after being exposed to the atmosphere for three or four minutes, took an inspiration, and moved his head a little; he then raised the end of his tail, though the middle of it was still stiff and did not bend when touched. His four legs remained close to his side, and were apparently useless; but on pricking them with the point of a lancet, they became convulsed. After being introduced into shallow water, he was able to crawl in a quarter of an hour, though his motions were very irregular. In an hour he was quite well. The animal in hydrogene appeared to have suffered very little in three quarters of an hour, and had raised himself against the side of the jar. At the end of an hour he was taken out, and very soon recovered.
b. Some hours after, the same lizards were again experimented upon. That which had been inserted into hydrogene in the last experiment, being now inserted into nitrous oxide.
This lizard was apparently lifeless in fourteen minutes, having tumbled and writhed himself very much during the first ten minutes. Taken out after being in twenty-five minutes, he did not recover. The other lizard lived in hydrogene for near an hour and quarter, taken out after an hour and twenty minutes, he was dead.
These animals were both opened, but the viscera of the nitrous oxide lizard were so much injured by the knife, that no accurate comparison of them with those of the other could be made, I thought that the lungs appeared rather redder.
c. Of two similar large water-lizards, one was introduced into a vessel standing over mercury, wholly filled with water that had been long boiled and suffered to cool under mercury.
The animal very often rose to the top of the jar as, if in search of air, during the first half hour; but shewed no other signs of uneasiness. At the end of three quarters of an hour, he became very weak, and appeared scarcely able to swim in the water. Taken out at the end of fifty minutes, he recovered.
The other was inserted into nitrous oxide. After much struggling, he became senseless in about fifteen minutes, and lay on his back. Taken out at the end of twenty minutes, he remained for a long time motionless and stiff, but in a quarter of an hour, began to move some of his limbs.
From these experiments, we may conclude, that water-lizards, and most probably the other amphibious animals, die in nitrous oxide in a much shorter time than in hydrogene or pure water; consequently their death in it cannot depend on the simple privation of atmospheric air.
At the season of the year in which this investigation was carried on, I was unable to procure frogs or toads. This I regret very much.