_Symptoms._—The incubation period varies from about five to ten days. The onset is very sudden, the temperature rising rapidly. Within an hour or two an initial rash appears, which varies in appearance and is transient. The patient suffers from severe headache and pain in the joints and back. Indeed, the condition closely resembles a sharp attack of influenza, but, as a rule, there are no signs of coryza. The eyes are very painful and insomnia is present. The high temperature lasts for three or four days, then drops, continues low from twelve hours to three days and rises again sharply. During the interval the patient feels better but the symptoms start again when the temperature rises for the second time. In the second stage the true rash of dengue appears, which is rather like that of measles, and it is followed by desquamation of the skin. The disease, though often causing great weakness, is very rarely fatal. _Prophylaxis._—Protect against mosquito bites by using a proper mosquito net or by employing mosquito repellents such as “sketofax.” _Treatment._—Light diet, rest in bed, phenacetin and aspirin for the relief of pain and headache. Cold sponging helps the febrile condition and the insomnia. During convalescence there is often much depression, and the patient benefits by being ordered tonics and a sound wine. _Diarrhœa._ Diarrhœa, or looseness of the bowels, is one of the most common and one of the most serious ailments of the tropics, and should never be neglected. In many cases it is a sign of enteric fever, dysentery, cholera, or sprue, the symptoms of which are given below. Ordinary attacks are usually due to the presence of some irritant in the bowels, such as irritating sand, bad food, unripe fruit, or other poisonous material. Amongst African and other natives diarrhœa is often due to a faulty or ill-cooked dietary. The importance of flies in fouling food should not be overlooked. _Treatment._—Begin the treatment by administering castor oil, fruit salt, cascara, or other mild aperient, to clear out the cause of the diarrhœa. If castor oil is used the following note as to its administration is likely to be of service. Place an ounce of brandy in a glass or cup. Carefully pour the oil into the centre of the brandy and then add one ounce of water. The mass of oil will then resemble the yolk of an egg enclosed in the white. Lime juice may be used instead of brandy. Failing these, black coffee helps to cover the taste and “feel” of the oil. Sometimes three grains of calomel with fifteen grains of sodium bicarbonate act better than castor oil. A warm-water enema of about a pint is useful. If the diarrhœa continues, give chlorodyne (20 minims) and tincture of ginger (10 minims) in an ounce of water two or three times a day. This treatment should not be persisted in for more than two days.