Since fixed air is not noxious _per se_, but, like fire, only in excess, I do not think it at all hazardous to attempt to _breathe_ it. It is however easily conveyed into the _stomach_, in natural or artificial Pyrmont water, in briskly-fermenting liquors, or a vegetable diet. It is even possible, that a considerable quantity of fixed air might be imbibed by the absorbing vessels of the skin, if the whole body, except the head, should be suspended over a vessel of strongly-fermenting liquor; and in some putrid disorders this treatment might be very salutary. If the body was exposed quite naked, there would be very little danger from the cold in this situation, and the air having freer access to the skin might produce a greater effect. Being no physician, I run no risk by throwing out these random, and perhaps whimsical proposals.[5] Having communicated my observations on fixed air, and especially my scheme of applying it by way of _clyster_ in putrid disorders, to Mr. Hey, an ingenious surgeon in Leeds a case presently occurred, in which he had an opportunity of giving it a trial; and mentioning it to Dr. Hird and Dr. Crowther, two physicians who attended the patient, they approved the scheme, and it was put in execution; both by applying the fixed air by way of clyster, and at the same time making the patient drink plentifully of liquors strongly impregnated with it. The event was such, that I requested Mr. Hey to draw up a particular account of the case, describing the whole of the treatment, that the public might be satisfied that this new application of fixed air is perfectly safe, and also, have an opportunity of judging how far it had the effect which I expected from it; and as the application is new, and not unpromising, I shall subjoin his letter to me on the subject, by way of _Appendix_ to these papers. When I began my inquires into the properties of different kinds of air, I engaged my friend Dr. Percival to attend to the _medicinal uses_ of them, being sensible that his knowledge of philosophy as well as of medicine would give him a singular advantage for this purpose. The result of his observations I shall also insert in the Appendix. FOOTNOTES: [5] Some time after these papers were first printed, I was pleased to find the same proposal in _Dr. Alexander's Experimental Essays_. SECTION V. _Of AIR in which a mixture of BRIMSTONE and FILINGS of IRON has stood._