_f._ A rabbit of a month old introduced into nitrous oxide, became senseless in less than a minute; the pulsations of the heart were very strong at this moment: they gradually became weaker, and in three minutes and half the animal was dead. _g._ Another rabbit of the same breed, after being rendered senseless in nitrous oxide in a minute and half, was taken out. He soon became convulsed; in a minute began to breathe quickly; in two minutes attempted to rise, but staggered, and fell again on his side. His hinder legs were paralytic for near five minutes. In twenty he had almost recovered. _h._ A middle sized guinea-pig was much convulsed, after being in nitrous oxide for a minute. In two minutes and half he was senseless. Taken out at this period, he remained for some minutes by the side of a warm fire, without moving; his fore legs then became convulsed; his hind legs were perfectly paralytic. In this state he continued, without attempting to rise or move, for near an hour, when he died. _i._ A large and old guinea-pig died in nitrous oxide, exhibiting the same phænomena as the other animals, in about five minutes and quarter. A young one was killed in three minutes and half. _j._ A small guinea-pig, after breathing nitrous oxide for a minute and half, was taken out, and placed before a warm fire. He was for a few minutes a little convulsed; but in a quarter of an hour got quite well, and did not relapse. _k._ A large mouse introduced into nitrous oxide, was for a few seconds very active. In half a minute he fell down senseless; in a minute and quarter he appeared perfectly dead. _l._ A mouse taken out of nitrous oxide, after being in it for half a minute, continued convulsed for some minutes, but finally recovered. _m._ A young hen was introduced into a vessel filled with nitrous oxide. She immediately began to struggle very much; fell on her breast in less than half a minute, and in two minutes was quite dead. _n._ A goldfinch died in nitrous oxide in less than a minute. In each of these experiments a certain absorption of the gas was always perceived, the water rising in the jar during the respiration of the animal. From them we learn 1st. That nitrous oxide is destructive when respired for a certain time to the warm-blooded animals, apparently previously exciting them to a great extent. 2dly. That when its operation is stopped before compleat exhaustion is brought on, the healthy living action is capable of being gradually reproduced, by enabling the animal to respire atmospheric air. 3dly. That exhaustion and death is produced in the small animals by nitrous oxide sooner than in the larger ones, and in young animals of the same species, in a shorter time than in old ones, as indeed Dr. Beddoes had conjectured a priori would be the case.