Both the right and left ventricles of the heart in F contracted but very feebly; the auricles regularly and quickly contracted; the aorta appeared perfectly full of blood. In E, a feeble contraction of the left sinus venosus and auricle was observed; the left ventricle did not contract: the right contracted, but more slowly than in F. In a few minutes, the contractions of the ventricles in F had ceased, whilst the auricles contracted as strongly and quickly as before. The blood in the pulmonary veins of F was rather of a redder purple than in E; the difference of the blood in the vena cava was hardly perceptible, perhaps it was a little more purple in F. The membranous substance of the lungs in F was spotted with purple as from extravasated blood, whilst that in E was pale. The brain in F was darker than in E. On opening the ventricles no extravasation of blood was perceptible. The auricles of the heart in F contracted strongly for near twenty minutes, and then gradually their motion became less frequent; in twenty-eight minutes it had wholly ceased. The right auricle and ventricle in E, occasionally contracted for half an hour. The livers of both animals were similar when they were first opened, of a dark red; that of F preserved its color for some time when exposed to the atmosphere; whilst that of E almost immediately became paler under the same circumstances. The peristaltic motion continued for nearly an equal time in both animals. _d._ The sternum of a young rabbit was removed so that the heart and lungs could be perceived, and he was introduced into a vessel filled with nitrous oxide; the blood in the pulmonary veins gradually became more purple, and the heart appeared to beat quicker than before, all the muscles contracting with great force. After he had been in about a minute, spots began to appear on the lungs, though the contractions of the heart became quicker and weaker; in three minutes and half he was quite dead; after death the ventricles contracted very feebly, though the contractions of the auricles were as strong almost after the end of five minutes as at first. This animal was passed through water saturated with nitrous oxide; possibly this fluid had some effect on his organs.