Page:Tropical Diseases.djvu/564

520 Anyone who has watched the movements of amœbæ on the warm stage can readily understand how such an organism might break down and separate the anatomical elements of a friable organ like the liver, and so cause a softening a cavity resembling an abscess. It feeds on the tissues, in fact, and to grow and multiply it must disintegrate their structures and consume their cells. Amœbæ occur much more frequently in liver abscess than is generally supposed; a circumstance strengthening the argument for regarding this parasite as being in causal relationship to that lesion, and therefore, pro tanto, to dysentery. In support of this statement, I may mention that recently Wenyon has produced not only amœbic dysentery but also liver abscess in cats by injecting stools containing large numbers of E. tetragena cysts, while similar experiments with E. coli cysts were uniformly negative.* 'Pathology of amœbic dysentery.— The main seat of the ulceration in amœbic dysentery is the large intestine; the small is rarely affected, though the lymphatic glands and liver may be invaded. Single or multiple abscesses of the latter organ are often concomitant features.

It is probable that amœbic lesions unmodified by bacterial action are rarely seen. In nearly every fatal case the mucous membrane is the subject of a secondary bacterial infection, so intense as to destroy all the amœbæ, which can in such cases be demonstrated only in the deeper layers of the intestinal 'wall. The ulcers, which are most numerous in the cæcum, hepatic, splenic, and sigmoid flexures, may be recognized by their circumscribed, punched-out appearance, the loss of tissue extending down to the muscular coats; the intervening mucous membrane may be normal or show varying degrees of inflammatory change. The coats of the intestine are much thickened; the degree of thickening depending on