Care must be taken as to the quality of the wire netting. We were put to a great deal of expense at Panama by sometimes getting wire netting that would last only two or three months. We finally adopted a specification requiring that our netting should be at least ninety per cent copper, allowing not more than ten per cent of non-corrosive metals. All netting was carefully tested to see that it came within these specifications. It was the very general opinion on the Isthmus that houses thus screened protected us much more thoroughly from insect life than is the case in most parts of the United States during the summer months. The dwellers in these houses habitually sat on the galleries, with electric lights burning, and would read for a whole evening without being disturbed by any kind of insect. The inspector had a man constantly employed patching holes and looking after the condition of this wire screening. In our barracks, in which forty or fifty Jamaican negroes lived, it was much more difficult to keep the wire netting in repair, and to keep the screened door of entrance closed, and some mosquitoes would always get in, if there were any mosquitoes around. In many of our stations we succeeded in entirely eliminating the mosquito, as in the district of Ancon. In such districts it made little difference as to the condition of the wire netting; in other districts where the anti-malarial work had been curtailed, mosquitoes were troublesome, and every day some would get into such barracks as I have described. For these cases Mr. Le Prince and his assistants developed a very effective method. They took an ordinary test tube, put at the bottom of it a few pieces of ordinary rubber, dropped on this rubber a few drops of chloroform and placed a small layer of absorbent cotton over it to keep it in place. When the mouth of this test tube is placed over the mosquito, she in a few seconds becomes narcotized by the chloroform and dies. This method of killing infected mosquitoes was developed by Mr. Le Prince and his sanitary inspectors into one of our most effective anti-malarial measures. It can be used where none of the other anti-malarial measures is possible.