follicles of the large intestine. The rest of the small intestine may be slightly injected, or may be normal. The mesenteric glands may be enlarged; other abdominal organs are normal. The intestinal contents consist usually of tenacious, slimy mucus intermingled with thick green fecal matter; fæcal matter may be absent, and merely blood-stained mucus resembling frog's spawn, or, on the other hand, solid fæces, may be found. Intestinal adhesions may occur, but perforation is extremely rare.
The microscopic pathology varies with the severity of the lesions. In the gangrenous form the epithelial cells of the mucous layer can no longer be distinguished, the whole of the mucous membrane undergoing coagulation necrosis with destruction of the glandular elements. The muscularis mucosse may be intact, or in places destroyed. The outstanding feature is the infiltration of the submucosa (Plate VIII.) and destruction of the nutrient blood-vessels. (These appearances are very similar to those produced in the large intestine of rabbits by intravenous injection of dysenteric toxins.) In subacute cases portions of the crypts can still be distinguished, but the cells stain badly and are vacuolated, and the submucosa is invaded by large wandering plasma cells, liable in sections to be mistaken for amœbæ. Dysentery and other bacilli can be seen crowding the mucous layer and in the lymphoid follicles, but bacilli are not found in the subinucous layer save where there is a break in continuity of the muscularis mucosæ. The muscular coat is normal.
By employing the appropriate technique (see p. 530) the dysentery bacillus can be isolated from the necrotic mucous membrane and also from the mesenteric glands, occasionally from the gall-bladder, but never from the blood.
AMŒBIC DYSENTERY
As distinguished from other forms the characteristics of this type of dysentery are, generally, insidious onset, marked tendency to chronicity, relapses alternating with periods of comparative quiescence, great
