_f._ To human blood that had been saturated with nitrous oxide whilst warm and constantly agitated for four or five minutes, to prevent its uniform coagulation, oxygene was introduced; the red purple on the surface of it, immediately changed to vermilion; and on agitation, this color was diffused through it. On comparing the tinge with that of oxygenated blood, no perceptible difference could be observed. No change of volume of the oxygene introduced, had taken place; and consequently, no nitrous oxide had been evolved from the blood. _g._ Blood, impregnated with nitrous gas, was exposed to oxygene; but after agitation in it for many minutes, no change of its dark purple tinge could be observed, though a slight diminution of the oxygene appeared to take place. _h._ Blood that had been rendered vermilion in every part by long agitation in atmospheric air, the coagulum of which was broken and diffused with the coagulable lymph through the serum, was exposed to nitrous oxide; for some minutes no perceptible change of color took place; but by agitation for two or three hours, it evidently affirmed a purple tinge, whilst a a slight absorption of gas took place. It never however, became nearly so dark as venous blood that had been exposed to nitrous oxide. _i._ Blood, oxygenated in the same manner as in the last experiment, the coagulum of which had been broken, was exposed to nitrous gas. The surface of it immediately became purple, and by agitation for a few minutes, this color was diffused through it. A slight diminution of the gas was observed. On comparing the tinge with that of venous blood that had been previously exposed to nitrous gas, there was no perceptible difference. _k._ Blood exposed to oxygenated muriatic acid is wholly altered in its constitution and physical properties, as has been often noticed; the coagulum becomes black in some parts, and brown and white in others. Venous blood, after agitation in hydrogene or nitrogene, oxygenates when exposed to the atmosphere in the same manner as simple venous blood. I had the curiosity to try whether venous blood exposed to hydrogene, would retain its power of being oxygenated longer than blood saturated with nitrous oxide: for this purpose some similar black coagulum was agitated for some time in two phials, one filled with hydrogene, the other with nitrous oxide. They were then suffered to rest for three days at a temperature from about 56° to 63°. After being opened, no offensive smell was perceived in either of them, the blood in hydrogene was rather darker than at the time of their exposure, whilst that in nitrous oxide was of a brighter purple. On being agitated for some time in the atmosphere, the blood in nitrous oxide became red, but not of so bright a tinge as oxygenated venous blood. The color of the blood in hydrogene did not at all alter.