Of all vegetable productions these are the most highly azotized, that is, animalized in their composition—a fact not only evinced by the strong cadaverous smell which some of them give out in decay, and by the savoury animalized meat which others afford at table, but on the evidence of chemistry also. Thus Dr. Marcet has proved that, like animals, they absorb a large quantity of oxygen, and disengage in return, from their surface, a large quantity of carbonic acid; all however do not exhale carbonic acid, but, in lieu of it, some give out hydrogen, and others azotic gas. They yield, moreover, to chemical analysis the several components of which animal structures are made up; many of them, in addition to sugar, gum, resin, a peculiar acid called fungic acid, and a variety of salts, furnish considerable quantities of albumen, adipocire, and osmazome, which last is that principle that gives its peculiar flavour to meat gravy. The Polyporus sulphureus is frequently covered with little crystals of the binoxalate of potash;[50] the Agaricus piperatus yields the acetate of potash,[51] and it is probable that other funguses of which we have as yet no recorded analysis will, on the institution of such, be found to contain some new and unexpected ingredient peculiar to themselves. When these several substances have been duly extracted from funguses, there is left behind for a common base the solid structure of the plant itself; this, which is called fungine, is white, flabby, insipid in its taste, but highly nutritious in its properties. If nitric acid be poured upon it, an immediate disengagement of azotic gas takes place, and several new substances are the result: a bitter principle, a reddish resinoid matter, hydrocyanic and oxalic acids, and two remarkable fatty substances, whereof one resembles tallow, the other wax. If dilute sulphuric acid be poured upon this fungine, no change ensues; but if muriatic acid be substituted, the result is a jelly.