_Lesions._ The alimentary canal is the main seat of morbid changes. The intestinal walls, and especially the mucosa, have points and patches of blood extravasation, extensive areas of congestion with ramified redness, exudation and thickening. The intestinal contents are watery, frothy, browned or blackened by effused blood, and swarming with ferments including the specific bacterium. The mucous surface is brownish or blackish, and epithelial degeneration and desquamation with abrasions are not uncommon especially on the summits of the duodenal folds and villi. Croupous exudates and swelling or ulceration of the follicles are met with. The lymph glands at the base of the cæcum are often enlarged and congested. The crop is full of watery, pulpy, frothy or slimy contents, and its mucosa and that of the pharynx may be deeply congested. Elsewhere the lesions suggest rather the action of destructive toxins and the profound changes in the blood. Pericardium and endocardium are usually studded with dark petechiæ, and congestion and even slight exudation may be present. The spleen is enlarged, soft, and gorged with blood. The liver is swollen, congested, extremely friable, and mottled, grayish white from degenerations. The kidneys are dark red, and friable. The lungs may show slight hyperæmia only, or a blood engorgement and consolidation, and are then easily reduced to a dark red pulp. Friedberger and Fröhner say that respiratory changes are most frequent in land birds; and intestinal and cardiac in water fowl. The blood is diffluent coagulating loosely if at all, of a brownish red color, reddening slowly and imperfectly in contact with air, and like the tissues contains an abundance of the characteristic bacterium staining deeply at the poles and clear in the center. In birds that survive a few days there are marked anæmia and emaciation, and the muscular system is of a grayish red color, with fatty degeneration. In acute and fulminant cases on the other hand the muscles may be full and of the normal red color. In arthritic cases the congestion and thickening of the soft tissues, and the excess of synovia, are supplemented by destruction of the articular cartilage and by areas of bone abrasion. In the more tardy cases collections of caseous matter are found.