Of the greatest value have been the observations of Stott. Using native Indian troops he gave one group (3931) prophylactic quinine while the other (3906) did not take quinine prophylactically. He continued this experiment one year giving 15 grains 3 times weekly for five months, and 10 grains 3 times weekly for the remaining seven months. Those taking quinine gave 170 primary admissions while those not taking it gave 179 (43.2 per thousand strength for the former as against 45.8 per thousand for those not taking quinine prophylaxis). Further observations were that those taking quinine prophylaxis showed a greater tendency to relapse, had somewhat longer fever, and required more quinine for treatment. Linnell states that he used quinine prophylaxis among 2000 coolies for a year, giving 5 grains or more daily with most discouraging results. It seemed to act as a slow poison and did not protect. _Quinine Immunity._—Bignami thinks that malarial relapses may be connected with insufficient initial treatment so that quinine-resisting forms survive and later, when some factor lowers the patient’s resistance, active multiplication of parasites, which are not readily destroyed by quinine, follows. While quinine prophylaxis may not be desirable on board ship, where one is in a position to readily recognize and treat the onset of malaria and to more or less efficiently carry out mosquito protection methods, or in a wealthy seaport, where sufficient interest in and funds for draining and screening exist, yet on military expeditions or exploring trips in tropical or subtropical countries it is the only practical method of keeping a force efficient. Of course, one should also utilize mosquito nets as assisting in protection from malaria, and as effective for yellow fever, dengue and filariasis. _Methods of Prophylaxis._—There are innumerable methods of carrying out quinine prophylaxis among which may be noted. (_a_) Celli’s method. In this there is given 3 grains of quinine each morning and 3 grains each night. Taken in this way Celli thinks that harmful effects from quinine are avoided, that quinine immunity does not occur and that there is no danger from quinine haemoglobinuria. For children he recommends the tannate in chocolate tablets. (_b_) In 1909 Bertrand and other members of a French Commission recommended two consecutive doses of 5 to 10 grains every seventh and eighth day for benign infections and two consecutive prophylactic doses of 10 to 15 grains every third and fourth days where malignant tertian was prevalent. (_c_) Ziemann gives 15 grains every fourth day with the idea that the quinine is entirely eliminated in four days. Nocht gives about 12 grains on two succeeding days of each week in divided doses of 2 or 3 grains instead of the entire amount in one dose. Koch gave 15 grains on tenth and eleventh days.