In the rumen, reticulum and manifolds, the mucosa and submucosa usually show limited areas of thickening and punctiform or arborescent congestion with softening and even detachment of the epithelium.
The abomasum is profoundly involved, especially in the vicinity of the pylorus. The folds are of a deep blood red or purple, or blackish, port wine hue, or they may be in part brownish red, or when necrotic, slate colored or mottled. The peptic glands are swollen, elevated and dilated, and patches and spots of softened and loosened epithelium are easily detached leaving a deep red surface with, it may be redder oozing points. Ulcerous sores may show on the summits of the folds. The contents are a viscous, fœtid grayish yellow, or reddish liquid, without solid ingesta.
The small intestines show similar lesions, deep, dark red congestions, most intense on the summits of the folds, softened, loosened, ragged patches of epithelium, erosions, ulcers, circumscribed sloughs, casts of the gut formed by desquamating epithelium, and congested, enlarged, and prominent aguimated and solitary glands are more or less in evidence. The contents are liquid and yellowish, grayish or reddish and fœtid. Microscopically the distension of the glands, (of duodenum, Lieberkuhn and Peyer), the proliferation and softening of the epithelium, the enlargement of the nuclei of these and of the cells of the submucosa, and the profusion of microörganisms are marked features.
In the cæcum and colon the lesions are usually less prominent, though swelling, softening and desquamation of the epithelium often exists, and points and patches of congestion, ecchymosis, and necrosis are not uncommon, particularly in the cæcum, and may extend to the muscular layer.
The terminal portion of the rectum is especially liable to marked congestion and blood extravasation, with more or less desquamation and erosion. The summits of the mucous folds are often of a dark red (port wine) hue, and as this is everted and exposed in defecation or later by the relaxation of the sphincter it becomes a marked lesion even in life.
The spleen is normal in strong contrast with anthrax in which similar gross lesions are often found on the mucosæ and especially the rectum.
The liver is usually rather pale and soft, as in other cases of high fever and centres of necrosis may be present. The gall bladder contains a variable amount of thin bile. The pancreas is nearly or quite normal. The lymph glands generally and especially those of the mesentery and abomasum are congested, enlarged and softened.
The kidneys are congested, often petechiated, swollen and softened, with centres of necrosis. The bladder, vagina and uterus show mucous congestion, and thickening uniformly or in spots with muco-purulent secretion.
The lungs show spots of hyperæmia, extravasation and at times hepatization, but a very characteristic lesion is the interlobular emphysema already referred to as connected with the abdominal pain and the sudden arrest of inspiration. This gives a gross appearance of marbling as in lung plague, only in this case the inflated interlobular tissue is dark colored instead of white as in lung plague, and it collapses at once when incised.
The encephalon, medulla and nerves present more or less hyperæmia and even exudation.