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502 as the slough forming the core of an ordinary boil. Another primary lesion described is the small abscess alluded to as elevating the mucous membrane and projecting into the lumen of the gut. These minute, pimple-like abscesses consist of a collection of gummy pus. After a time a tiny opening forms at the apex of the little swellings, through which the contents may be expressed: it is this opening which, it is alleged, forms, on enlarging, the specific ulcer of dysentery. Assuming that there are several specific causes for dysentery, it is to be expected that the corresponding primary lesions should differ; that whilst one causes a suppurating or a gangrenous lesion, another may produce a croupous or a diphtheritic; that whilst one species of dysenteric germ attacks the mucosa, another species may select the submucosa; one may attack the glandular structures, another the connective tissue, another the epithelial layer. Whatever the primary lesion may be, eventually the weakened tissues are attacked by the ordinary bacteria of suppuration; so that finally, if the cases survive long enough, they all present a certain uniformity as regards the ultimate ulceration, thickenings, and other inflammatory lesions disclosed post mortem.

Healing process.— The dysenteric ulcer heals partly by contraction, partly by the formation of a very thin scar tissue scar tissue which, besides contracting, is apt to become pigmented. Lost glandular structures are never reproduced. Owing to the constant peristaltic movement of the gut, and the passage of fæces over the face of the healing ulcer, cicatrization, as might be supposed, is a slow process, and one prone to interruption by recurring attacks of inflammation of a more or less specific nature.

Lesions in chronic dysentery.— In chronic dysentery the ulcers are usually smaller and less numerous than in the acute disease. They are also less ragged in outline, tending to become circular in shape and to acquire thickened rather than undermined edges. Cicatricial bands and contractions may narrow the lumen of the gut, the functions of which are still further hampered by thickenings, or by adhesions which unite