To ascertain the nature of the residuum, it was necessary to transfer it into another vessel, but this I found very difficult to accomplish, on account of the coagulated blood. By piercing through the coagulum and removing part of it by means of curved iron forceps, I at last contrived to introduce about 4½ measures of the gas into a small cylinder, graduated to,25 cubic inches, in which it occupied of course, nearly 9 measures; when a little solution of strontian was admitted to these, it became very slightly clouded; but the absorption that took place did not more than equal half its bulk. Consequently, the quantity of carbonic acid evolved from the blood, or formed, must have been extremely minute. On the introduction of pure water, a rapid absorption of the gas took place, and after agitation, not quite 3 measures remained. These did not _perceptibly_ diminish with nitrous gas; their quantity was too small to be examined by any other test; but there is reason to suppose that they were chiefly composed of nitrogene. From this experiment, it appeared that nitrous oxide is absorbed when placed in contact with venous blood; at the same time, that a very minute quantity of carbonic acid and probably nitrogene is produced. _c._ In another similar experiment when nearly half a cubic inch of nitrous oxide was absorbed by about a cubic inch and three quarters of fluid blood, the residual gas did not equal more than ⅛, the quantity absorbed being taken as unity. This fact induced me to suppose that the absorption of nitrous oxide by venous blood, was owing to a simple solution of the gas in that fluid, analogous to its solution in water or alcohol. To ascertain if nitrous oxide could be expelled from blood impregnated with it, by heat; I introduced to 2 cubic inches of fluid blood taken from the medial vein, about,6 cubic inches of nitrous oxide. After agitation, in seven minutes nearly,4 were absorbed. In ten minutes, after the blood had completely coagulated, the cylinder containing it, was transferred in contact with mercury, into a vessel of solution of salt in water; this solution was heated and made to boil. During its ebullition, the whole of the blood became either white or pale brown, and formed a solid coherent mass; whilst small globules of gas were given out from it. In a few minutes, about,25 of gas had collected. After the vessel had cooled, I attempted to transfer this gas into a small graduated jar in the mercurial apparatus, but in vain; the mass in the jar was so solid and tough, that I could not remove it. By transferring it to the water apparatus, I succeeded in displacing enough of the coagulum to suffer the water to come in contact with the gas; an absorption of nearly half of it took place; hence, _I conjecture_, that nitrous oxide had been given out by the impregnated blood.