(_d_) Castellani’s method of 5 grains daily and a double dose once a week is the one I recommend. _Sterilization of Carriers._—In addition to quinine prophylaxis for those not infected we also have quinine disinfection for native or other carriers of malaria. For these infected persons Koch recommends 15 grains on two to three successive days of each week, the course to be continued for three months. This plan of extirpation of the parasites of _malarial carriers_ is of great practical application. Gill uses 10 grains of quinine daily for six months after discharge from hospital. The effect of tartar emetic on malarial gametes may prove of value. =Treatment.=—Cinchona bark was first introduced into Europe in 1640 and has its name from Countess Chinchon, wife of the Peruvian Viceroy, who was cured of a fever by this bark in 1638. Much of our knowledge of the therapeutics of cinchona bark is due to Torti. In giving the drug he used a large dose the first day and the same for the subsequent two days. After that he administered smaller doses for a week and then still smaller doses for two or three weeks. Quinine was not introduced until 1820. At present quinine or some salt of the alkaloid is used in malaria instead of preparations of cinchona bark. _Toxic Effects of Quinine._—The most important untoward manifestations of cinchonism are the very common scarlatiniform, eczematous or urticarial rashes, gastric disturbances and vertigo. Impairment of vision may be brought about by quinine and quinine haemoglobinuria is a recognized possibility. In quinine amblyopia the pupils do not react to light and the optic disc is very pale, thus distinguishing the impairment of vision due to the plugging of the retinal vessels by the malarial parasite, in which condition the pupils do react to light and the disc is a grayish red. _Quinine Idiosyncrasy._—Fortunately the taking of quinine is well borne by the great majority of persons but in exceptional cases we may have developing, even after doses as small as one grain, of (_a_) severe nausea vomiting or diarrhoea, (_b_) various skin eruptions, usually of a scarlatiniform or urticarial type, (_c_) marked ringing in the ears, dizziness or deafness, (_d_) impairment of vision, (_e_) dyspnoea and (_f_) malarial haemoglobinuria. To determine an idiosyncrasy make a scratch on the flexor surface of the forearm and apply a drop of a 1 to 10 solution of quinine. Oedema with a wide zone of erythema in about 5 minutes shows idiosyncrasy. A control with normal saline should be made. It is well to make this skin test before giving quinine intravenously. For desensitization we give 1/10 grain of quinine combined with 5 grains of bicarbonate of soda and in about 1½ hours we give 1 grain with 5 grains of bicarbonate of soda.