the chronicity of the infection; they may be matted together and adherent to the liver and spleen. The intestines themselves are very friable and easily tear when handled.
In chronic cases polypoid gangrenous tags of mucous membrane hang into the lumen of the gut. The surface of isolated ulcers may be covered with large yellow and gangrenous sloughs. The intestinal contents in these cases are composed of dark, almost black hæmorrhagic fæcal matter possessing a characteristic penetrating odour. Circumscribed areas of the large intestine, or the entire mucosa, may be thus affected, and may then resemble lesions of bacillary origin in which extensive sloughing has taken place. Perforation of the large intestine, resulting in purulent peritonitis, is common. Ulceration of the appendix may also be found. Contractions often leading to occlusion and scars, and pigmentation at the seat of old ulcerations, are commonly encountered in juxta-position to areas of bowel in which the process is still active.
Microscopic sections through an amœbic ulcer (Fig. 81) reveal amœbæ invading the submucous coat. There are subacute concomitant inflammatory changes. The blood-vessels are dilated. There are no hæmorrhages, but the tissue reaction, as evidenced by invasion by fibroblasts and by round-cell infiltration, is not marked. Red blood-corpuscles may often be demonstrated inside the amœbæ. In more extensive cases, where ulceration has extended into the circular muscular coat, amœbæ may be seen penetrating between the fibres and even inside the dilated capillary vessels of the serous coat.
The adjacent apparently healthy mucous membrane shows comparatively few microscopic changes ; there is some round-cell infiltration of the interstitial tissue, into which amœbæ may be seen penetrating and actually lying within the crypts of Lieberkiihn. Bacilli can be demonstrated in great numbers in the superficial layers of the ulcer. The amœbæ can be stained in sections by hæmatoxylin and eosin or by iron hæmatoxylin (see p. 529). In
