Enteritis consists in inflammation of the intestine, or, more precisely, in inflammation of the intestinal mucous membrane. All the constituent portions of the intestinal tube may be affected (duodenum, jejeunum, ileum, colon, cæcum); but clinical distinctions and localisation of inflammation in the various parts are very difficult in the domesticated animals, and at present it is impossible to describe with any accuracy the differences between duodenitis, enteritis of the jejeunum and ileum, colitis or typhlitis. Without doubt certain symptoms suggest that some regions are more affected than others; but clinically we are only able to distinguish between acute and chronic enteritis. Acute enteritis may assume different forms, according to its intensity, rapidity of development, and lesions, so that it is possible to distinguish between such conditions as simple acute enteritis and hæmorrhagic enteritis. Chronic enteritis, an abstraction founded on our knowledge of such specific forms of enteritis as are due to tuberculosis, distomatosis, helminthiasis, etc., usually assumes the diarrhœic form. ACUTE ENTERITIS. As acute enteritis, whether localised in one portion of the intestine or involving the whole intestinal tube, is produced by varying causes, and assumes very varying degrees of intensity, its clinical symptoms are equally diverse. =Causation.= The various forms of enteritis result from two great series of causes: infections and intoxications. Normally the intestine contains an extremely large number of different microbes, which may prove of service so long as circulation, secretion, and peristalsis continue normal; but as soon as any perturbation occurs, either in the blood supply or in the movement of the bowel, normal secretion is impeded; abnormal organic fermentation commences, producing irritant principles or toxins which at once set up local irritation, or, being absorbed, produce that complex of symptoms which we recognise as enteritis, intoxication of intestinal origin, or even infection. Bearing in mind these facts, we are better able to understand the part played by cold, by damaged fodder, by intense, stimulating feeding, or sudden changes in the food, as well as by the action of drastic purgatives, which modify beyond physiological limits the condition of the glands, or even cause local desquamation of epithelium. Toxic substances or plants act similarly by modifying either the circulatory, secretory, or motor systems. =Symptoms.= The first appreciable external symptoms appear to result from fever—loss of appetite, suspension of rumination, dryness of the muzzle and of the mouth, earthy-red colour of the conjunctival mucous membrane, etc. On manipulating the left flank one notes neither tympanites nor sensitiveness—in a word, there is no indication of functional disturbance of the rumen.