Malaria is, however, a very different proposition. A corresponding crusade has been carried on for six years against the little _anopheles_ gnat, the little criminal who carries the malarial poison. His happy breeding-grounds are in open country marshes and pools, and there is no lack of these in the canal zone. It was impossible to deal with the entire three-quarters of a million acres of that territory, but wherever the canal workers were settled determined war was waged against the mosquitoes. It should be remembered that the _anopheles_ can fly only about a hundred or two hundred yards. The jungle was therefore cleared away for a few hundred yards round each village and settlement, marshes and pools in this area were drained off, and into all the ditches where stagnant water had collected oil was poured, which so effectually turns the mosquito's stomach that it never recovers. Some 1,200 acres of the zone were thus treated, and of course the regulations as to house-screening applied to malaria no less than to yellow fever. The employees were also supplied freely and generously with quinine. The result has been not the eradication of malaria, but the reduction of the cases to about one-third the number at which they stood in 1906. Yet even so, among the 40,000 employees on the canal during the year ending June 30, 1912, there were 7,000 malaria cases in the hospitals, with 32 deaths, 22 of these being white people. The heavy rainfalls at the isthmus will probably prevent the complete sanitation of the country in this respect, for the simple reason that the destruction of the _anopheles_ mosquito or the eradication of the malarial germ can never be complete. There will always be people going about with the malarial organism in their blood, and always _anopheles_ mosquitoes ready to become infected with it and to carry the infection about. But, as we have seen, much can be done by the means described to reduce the ravages of the disease. In 1906, out of a working force of 26,000, there were 21,739 cases of malaria. We have seen how this figure had been brought down in 1912. In 1906 it was almost certain that any white person coming to reside at the isthmus would catch malaria. Now it is quite possible to live there in perfect health, quite free from any malarial infection.