Probably, if the French had been trying to propagate yellow fever, they could not have provided conditions better adapted for this purpose than the conditions which they did establish with an entirely different object. The stegomyia were bred everywhere about the Ancon Hospital grounds in the usual numbers found in almost every tropical community, due to old cans, bottles, rain-water barrels, roof gutters, etc. As I have mentioned before, the grounds were most beautifully laid off and every kind of tropical bush and shrub carefully fostered in the various plots about the grounds. There is down there a large ant, known as the umbrella ant, that is very destructive to most shrubs and plants. A colony of these ants will, in the course of a single night, cut every leaf from a good-sized orange tree. The leaf is cut into a piece about half an inch in diameter and carried off by the ant in his nippers, and when you see a column of these ants crossing the path, hundreds and thousands of them, with these circular pieces of leaves in their nippers, it looks very much as if they were carrying them for protection against the sun. Hence their name, “umbrella ant.” Now, in order to raise any vegetation at Ancon, the plant has to be protected from these ants. The French used for this purpose a pottery ring. The ring was filled with water and the plant was placed in the large hole in the center. This thoroughly protected the plant, as the ant was unable to cross the water. But the water in the ring was an ideal breeding-place for the stegomyia mosquito, and as there were several thousand of these earthenware rings about the grounds, close to the wards, a more perfect arrangement for the propagation of yellow fever could not have been adopted, if the authorities had this object in view. Knowing that shrubbery protected and harbored mosquitoes, we cleared off, as was our rule, everything within two hundred yards of any of the buildings. It looked very much like vandalism on our part to see all the beautiful plants, rose bushes, flowers, etc., which had been for so many years carefully nurtured and cared for by our French predecessors, ruthlessly destroyed. But our work was successful, and in the course of time we got rid of mosquitoes entirely in the grounds of Ancon Hospital. We continued to keep the buildings well screened, however, though I feel sure that we could now treat cases of yellow fever in Ancon Hospital in unscreened wards and still not have the disease transmitted to the non-immunes in the ward, for the reason that there are no stegomyia there to transmit the disease. This statement is not altogether theory on my part.