_Symptoms._—Diarrhœa with pains in the belly, straining and frequent desire to go to stool. The motions soon become small in amount, slimy, lose their natural colour, and contain more or less blood; when there is ulceration of the coats of the bowel, the motions are extremely offensive, and bleeding may be very free. There is heat, tenderness, and bearing down about the outlet of the bowel, with considerable prostration and probably some fever; there is frequently a constant desire to pass water. All these symptoms may be due to severe ordinary diarrhœa; but in the tropics it is best to treat them as if they were dysenteric. Some guide may be obtained as to the form of dysentery from which the patient is suffering by taking his temperature. As a rule there is little or no fever associated with the amœbic form, while in the case of the bacillary type the temperature is always raised and in severe cases may be considerably elevated. It is in this form that the small intestine is apt to become involved and then the condition is more serious. One help in diagnosis, though not a very reliable one, is the character of the stool. In amœbic dysentery the blood is apt to be mixed with the dejecta and to be dark in colour, while the whole mass looks brown or greyish green. The stool of bacillary dysentery, on the other hand, has a whitish appearance, the blood in it is bright coloured and is often in the form of streaks or spots. The amœbic form is apt, if not promptly and efficiently treated, to be followed by inflammation of the liver, which may go on to liver abscess. _Prophylaxis._—Avoid chill and debilitating causes of all kinds. In countries where there is a great difference between the day and the night temperature wear a cholera belt. Carefully protect food and water from contamination of any kind, and especially from flies. Doubtful water should be boiled or rendered sterile by some chemical method. All milk should be boiled. Care should be taken not to employ as cooks natives who have recently suffered from dysentery, and scrupulous cleanliness should be observed in the preparation of food. Unripe fruit and other materials apt to cause diarrhœa should be avoided. Camp conservancy methods should be carried out on approved sanitary principles which prevent the access of flies to human excrement and prevent the latter from being disseminated by wind or in any other way. All dysenteric stools should be carefully disinfected or burnt. _Treatment._—The general treatment is common to both forms, the essentials being rest, warmth and suitable food. Put the patient to bed, apply a cholera belt and get the bowels open by an initial dose of castor oil. If there is much pain ten drops of tincture of opium may be added to the oil. The usual dose of the oil is an ounce, but if the patient is feeble or exhausted half an ounce will be sufficient.