Dr. Reed here considers a squad of fifty men doing sanitary work in a city of two hundred thousand inhabitants at large. Four years afterwards, in the city of Panama, a place of twenty thousand inhabitants, we had six hundred men doing the same work. Major Reed is inclined to think fifty pounds of pyrethrum to a case a large amount. In 1905 in Panama we used two hundred and forty thousand pounds during the year. I call attention to this as showing how little any of us appreciated the magnitude of the job when we first started in. (5) Havana, Cuba, June 13, 1901. MY DEAR REED: Yours of June 5th received. I inclose you a copy of Dr. Guiteras’ report for May. We see still no success from our inoculations in twenty-two cases, but the great “but” comes in. I am not sure that any of the cases bitten were yellow fever. One of the last, from Tampico, I thought a pretty well marked case, though not dangerously ill, but his mosquitoes, on the 20th day, did not infect. I am disappointed beyond measure. I had hoped by this time to have Las Animas full to overflowing with inoculated cases, and be turning out immunes at the rate of some two hundred a month. But may be it is well as it is; in our enthusiasm we might have infected the city. No case of yellow fever since May 7th, and still none on hand. The Board diagnosed one early in the month, but it turned out a well-marked case of typhoid fever. Of course I agree with you that nothing very definite can be deduced from our results this early in the season, though personally I am very much impressed by them. Our condition now is very much better than it was even in ’99, with regard to yellow fever, and of course our liability to it is very much better. ’98 and ’99, with regard to yellow fever, should be left out, as in these years there were no non-immunes in Havana, and they would not have had yellow fever no matter what the condition of infection would have been. I except of course, the latter part of ’99. From the 1st of March to the 16th of June in ’99 (and mind you this has been far and away the best record Havana ever made), we had four deaths from yellow fever. In the same period this year, we have had one, which occurred March 16th. The deaths in ’99 occurred scattered over this period. It seems to me that the present condition of affairs indicates that we have been doing something that has had a great effect upon infection; and of course the only thing we have done this year that we did not do last year is the destruction of the mosquito. We commenced this work about the middle of February, just about the time that yellow fever practically disappears.