Abstract
'Chronic relapsing pancreatitis' was seen in 81 per cent of 108 rats of 3 inbred strains. Clinically, even in advanced cases, there were no symptoms of disease and the physical status of the animals was satisfactory. The least histological sign of involvement was a decrease or loss of cytoplasmic basophilia in acinar cells in some lobules, and infiltration of the intralobular connective tissue by mononuclear cells. More severe forms of the disease were characterized by flattening of the epithelium of acini by 'microcystic-transformation' of the gland, and fatty atrophy. Fibrosis of the connective tissue and dilatation of the ducts were usual events. In few cases 'polyarteritis-like' lesions of the arteries of the pancreas were observed. Microbiological investigation of the aetiology is in progress.