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XXIX] the surface of the former is softened, perhaps eroded, arid covered with a blood-streaked glairy mucus of the same character as that which appears in the stools.

Ulcerative and gangrenous dysentery.— Cases of catarrhal dysentery rarely die; the exact conditions of the mucous membrane, therefore, in these cases can only be conjectured. It is otherwise in the severer forms of the disease. When such cases come to the post-mortem table the mucous membrane of the large intestine and, very frequently, a foot or two of the lower end of the ileum are found to be thickened, congested, inflamed, speckled perhaps with ecchymoses, œdematous, and more or less riddled with ulcers or patches of gangrene of various sizes, shapes, and depths. As a rule, the brunt of the disease falls on the sigmoid flexure and descending colon; not infrequently, the lesions are equally if not more advanced in the cæcum and ascending colon, and may involve a foot or two of the lower end of the ileum. On the whole, the transverse colon, though often seriously implicated, is so to a less extent than one or other of the parts mentioned, or than the hepatic and splenic flexures. The dysenteric ulcer varies in size from a punched-out-looking sore the size of a pea, or even less, to a patch several inches in diameter. As a rule, in the earlier days of the acute stage the ulcers tend to follow the folds of the mucous membrane, the free borders of which are the parts most liable to implication. The edges of the sores are ragged and undermined, the floor is sloughy and grey. There may be considerable thickening of the edges and base of the ulcer, and there may be peritoneal adhesions. The appearance of the ulcer may suggest that it extends by a process of burrowing in the submucosa, the superjacent membrane sloughing or disintegrating in consequence of the destruction of its subjacent nutrient vessels. This burrowing may extend for a considerable distance beyond the apparent margin of ulceration; so much so that long, suppurating, fistulous tunnels may connect one ulcer with another. In this way large patches of mucous membrane come to be undermined, and