DIVISION II.
Of the CHANGES effected in NITROUS OXIDE, and other GASES, by the RESPIRATION of ANIMALS.
I. Preliminaries.
As soon as I had discovered that nitrous oxide was respirable, and possessed of extraordinary powers of action on living beings, I was anxious to be acquainted with the changes effected in it by the venous blood. To investigate these changes, appeared at first a simple problem; I soon however found that it involved much preliminary knowledge of the chemical properties and affinities of nitrous oxide. After I had ascertained by experiments detailed in the preceding Researches, the composition of this gas its combinations, and the physical changes effected by it in living beings, I began my enquiry relating to the mode of its operation.
Finding that the residual gas of nitrous oxide after it had been breathed for some time in silk bags, was chiefly nitrogene, I at first conjectured that nitrous oxide was decomposed in respiration in the same manner as atmospheric air, and its oxygene only combined with the venous blood; the following experiments soon however convinced me of my error.
II. Absorption of Nitrous Oxide by venous blood.
Changes effected in the blood by different Gases.
a. Though the laws of the coagulability of the blood are unknown, yet we are certain that at the moment of coagulation, a perfectly new arrangement of its principles takes place; consequently, their powers of combination must be newly modified. The affinities of living blood can only be ascertained during its circulation in the vessels of animals. At the moment of effusion from those vessels, it begins to pass through a series of changes, which first produce coagulation, and finally its compleat decomposition.
Consequently, the action of fluid blood upon gates out of the vessels, will be more analogous to that of circulating blood in proportion as it is more speedily placed in contact with them.
b. To ascertain the changes effected in nitrous oxide by fluid venous blood.
A jar, six inches long and half an inch wide, graduated to,05 cubic inches, having a tight stopper adapted to it, was filled with nitrogene, which is a gas incapable of combining with, and possessing no power of a action upon venous blood. A large orifice was made in the vein of a tolerably healthy man, and the stopper removed from the jar, which was brought in contact with the arm so as to receive the blood, and pressed close against the skin, in such a way as to leave an orifice just sufficient for the escape of the nitrogene, as the blood flowed in. When the jar was full, it was closed, and carried to the pneumatic apparatus, the mercury of which had been previously a little warmed. A small quantity of the blood was transferred into another jar to make room for the gas. The remaining quantity equalled exactly two cubic inches; to this was introduced as speedily as possible, eleven measures equal to,55 cubic inches of nitrous oxide, which left a residuum of ¹/₃₂ only, when absorbed by boiled water, and was consequently, perfectly pure. On agitation, a rapid diminution of the gas took place.