Governor Magoon arrived at the isthmus in May 1905, just as the yellow fever epidemic was reaching its climax. From that moment he and Colonel Gorgas, to whom he gave the most complete support, set themselves to fight the fever. The first thing to do was to get all the patients within screened buildings, whether the hospital or their own homes, so that no _stegomyia_ mosquitoes could saunter in and take the poison. Then the towns of Colon and Panama were handed over to a campaign of spring-cleaning such as the world has never witnessed. Then the canal building was thoroughly fumigated with pyrethrum powder or sulphur, and not simply the official building but every single house in the city of Panama was similarly disinfected. Dust and refuse were everywhere burnt. A very efficient system of inspection was adopted, and a rigid quarantine enforced against all foreign places whence the yellow plague could be imported into the zone. But more important than the immediate expedients were the more permanent sanitary improvements carried out in Colon and Panama. These towns were repaired with brick or cement, and provided with what they had never yet enjoyed, a proper system of drainage. Waterworks were also constructed outside the towns, and a supply of pure water made available for every household. Hitherto water had had to be stored during the dry season in tanks and cisterns, in which the _stegomyia_ mosquito revelled exceedingly. These were now no longer necessary, and stagnant water, wherever it collected in the town, was drained away. In order to expedite these splendid reforms, Governor Magoon withdrew the workers from the canal and concentrated all efforts on the sewers and waterworks. So speedily was the work carried forward that the water was turned on for public use from the main in the Cathedral Plaza on July 4. The results of this drastic campaign were soon apparent in the dwindling of the yellow fever returns. In July there were still forty-two cases and thirteen deaths on the isthmus, with twenty-seven cases and ten deaths among the employees. August showed a great improvement, with twenty-seven cases and nine deaths on the isthmus, and twelve cases and only one death on the canal. The improvement continued through September, October, November, and in December only one case was reported on the isthmus and one on the canal. Three months having elapsed since the last case, and, therefore, every _stegomyia_ which could possibly be infected with malaria having departed this life, the epidemic was entirely past and over. As I have pointed out, there cannot possibly be any return of it under these conditions unless the infection is brought from without. And if any new cases are at once isolated and screened from afternoon calls of the mosquito, the outbreak may be easily and infallibly suppressed. We may say, therefore, that the yellow spectre at the isthmus has been shorn of all its terrors.