The screening was very carefully done under the supervision of Mr. Le Prince, who formerly had charge of similar work at Havana. Only one entrance was used for each ward, and this entrance was closed by a screened vestibule, with double doors. A watchman was always on duty in this vestibule, whose business it was to see that any person entering the vestibule from the outer door, closed the outer door before opening the inner. Notwithstanding the large number of cases of yellow fever treated in the yellow-fever wards of Ancon Hospital in the years 1904 and 1905, and in spite of the fact that in these wards were a considerable number of non-immune patients who did not have yellow fever, and the further fact that most of the doctors and nurses were non-immunes, not a single case of yellow fever developed in Ancon Hospital during American control of that institution. I wish to except from this statement one of the female nurses. This nurse did have a very severe case, and came very near dying. The evidence seemed very strong that she had not contracted the disease in the hospital. She was in the habit of going down frequently into the city of Panama in the evening after sunset where infection was very rife. Soon after her recovery she married one of the young doctors connected with the hospital upon whom public opinion settled the blame for her contracting the disease, because he had so frequently inveigled her into taking trips into town. That no case of yellow-fever infection occurred in the hospital is the greatest possible compliment to the efficiency of the system established by the authorities for its prevention. It made a very strong impression both upon the Americans and Panamanians. All could see that we had done something that had radically changed conditions as they had existed before in Ancon Hospital. Formerly, nearly every white non-immune who was taken to the hospital developed yellow fever. Now, they could see that the yellow-fever wards of Ancon Hospital were safer for a non-immune than was any part of the city of Panama. When it was explained to them that there was no mystery about this; that it had been discovered that yellow fever could not be conveyed from man to man except by the stegomyia mosquito, they were prepared to accept this as the proper explanation.