The preceding observations will enable the medical jurist to determine, how far a diagnosis may be drawn from the symptoms between poisoning with the irritant and the diseases which resemble it. It will be remarked that the most embarrassing disease, on account of its frequency, and peculiar symptoms, is cholera. Cholera, however, may be recognised in some instances even considered in regard to the irritants as a class; and we shall presently find that it may be distinguished still better from the effects of some individual poisons. SECTION II.—_Of the Morbid Appearances caused by Irritant Poisons, compared with those of certain natural diseases._ The next subject for consideration is the morbid appearances produced by the irritants as a class, together with those of a similar nature, which arise from natural causes. The powerful irritants, which are not corrosives, produce simply the appearances characteristic of inflammation of the alimentary canal in its various stages,—in the mouth, throat, and gullet vascularity, and also, if the case has lasted long enough, ulceration;—in the stomach, vascularity, extravasation of blood under and in the substance of the villous coat and likewise into the cavity of the organ, abundant secretion of tough mucus, deposition of coagulable lymph in a fine network, ulceration of the membranes, occasionally perforation, preternatural softness of the whole or of part of the villous coat, and on the other hand sometimes uncommon hardness and shrivelling of that coat; in the intestines vascularity, extravasation, and ulceration.—Sometimes several of these appearances are to be seen in the whole alimentary canal at once. In poisoning with arsenic or corrosive sublimate it is no unusual thing to meet with redness or ulceration of the throat, great disease in the stomach, vascularity of the small intestines, ulcers in the great intestines, and excoriation of the anus.—When the poison is an active corrosive much more extensive ravages are sometimes caused, particularly in the stomach. After poisoning by the mineral acids, for example, the whole mucous membrane of the stomach is at times found wanting; nay, large patches of the whole coats may be wanting, and the deficiency supplied by the adhesion of the margin of the aperture to the adjoining viscera, and the conversion of the outer membrane of these viscera into an inner membrane for the stomach. Of the appearances here briefly enumerated the particulars will be related partly under what is now to be said of the appearances arising from natural causes, which are liable to be confounded with the effects of poisons, partly under the head of individual poisons. _Of redness of the stomach and intestines from natural causes, and its distinction from the redness caused by poisons._