[228] See Dr. Beddoes’s _Considerations_, _part_ 1. _page_ 26. His observations in the note in the last section, will likewise apply here.—Is not healthy living action dependant upon a certain equilibrium between the principles supplied to the blood by the pulmonary veins from respiration and by the lymphatics from absorption? Does not sensibility more immediately depend upon respiration? Deprive an animal under stimulation, of air, and it instantly dies; probably if absorption could be prevented, it would likewise speedily die. It would be curious to try whether intoxication from fermented liquors cannot be prevented by breathing during their operation, an atmosphere deprived of part of its oxygene. By this oxygene and nutritive matter excitability may be kept up: and exhaustion consequent to excitement only produced, in consequence of a deficiency of some of the nutritive principles, which are supplied by absorption. When nitrous oxide is breathed, nitrogene (a principle under common circumstances chiefly carried into the blood by the absorbents in fluid compounds) is supplied in respiration; a greater quantity of oxygene is combined with the blood than in common respiration, whilst less carbonic acid and probably less water are evolved. Hence a smaller quantity of nutritive matter is probably required from the absorbents during the excitement from nitrous oxide, than during the operation of stimulants; and in consequence, exhaustion from the expenditure of nutritive matter more seldom occasioned. Since Research III. has been printed, I have endeavoured to ascertain the quantities of nitrogene produced when nitrous oxide is respired for a considerable time. In one experiment, when I breathed about four quarts of gas in a glass bell over impregnated water for near a minute, it was diminished to about two quarts; and the residuum extinguished flame. Now the experiments in Research II. prove that when nitrous oxide is decomposed by combustible bodies, the quantity of nitrogene evolved is rather greater in volume than the pre-existing nitrous oxide. Hence much of the nitrogene taken into the system during the respiration of nitrous oxide, must be either carried into new combinations, or given out by the capillary vessels through the skin. It would be curious to ascertain whether the quantity of ammoniac in the saline matters held in solution by the secreted fluids is increased after the respiration of nitrous oxide. Experiments made upon the consumption of nitrous oxide mingled with atmospheric air by the smaller animals, would go far to determine whether any nitrogene is given out through the skin. The various effects of nitrous oxide upon different individuals and upon the same individuals at different times, prove that its powers are capable of being modified both by the peculiar condition of organs, and by the state of general feeling.