Histopathological studies were carried out on the gastro-intestinal tract, mainly the abomasum, of 113 out of 558 Japanese steers and dairy cattle received by the Sasayama and other slaughterhouses in Hyogo, Ishikawa, and Ehid Prefectures during a period of 9 years from 1955 to 1963. The following results were obtained.
1. Principal lesions observed on the abomasum were erosion, ulcer, and atrophy of the mucous membrane. Of the 113 cases examined, 74 cases (65.8%) had erosion, 10 cases (8.8%) ulcer, and 16 cases (14.2%) atrophy.
2. Erosion must have developed in the abomasum not only from trauma produced by the ingestion of foreign bodies, but also from necrosis and desquamation of the epithelium. These changes had been brought about by atrophy of the cells of the mucous membrane and reduction of its defense mechanism due to hemorrhage or local metabolic disturbances, in addition to the function of gastric juice. At the same time, degeneration and necrosis must have expanded into the surrounding tissues.
3. Ulcer developed progressively after lesions had broken through the muscularis mucosae as the result of marked cellular infiltration. It developed also spontaneously from the necrotic process in the deeper part of the mucous membrane, together with edema and leukocyte infiltration. Vegetable fibers piercing the base of an ulcer were found in 3 cases (33.3%) of the 10 examined.
4. Atrophy, necrosis, and disappearance of the mucous membrane occurred not only by hyperplasia of lymphatic tissue but also by devitalization of epithelial cells and circulatory cisturbance.
