To meet this condition of affairs, as soon as the case was concluded, the house in which the patient had been sick and all the contiguous houses were fumigated with such material as would kill the mosquitoes. In order that the fumigation might be effective the house had to be carefully gone over and all cracks and crevices stopped, so as to make the building as nearly air-tight as in the nature of things it could be made. This was a very laborious process and required care and expert supervision. Most of the stopping of crevices was done with paper and paste. Sulphur is probably the most effective substance in killing the mosquito. The rolled sulphur was used at the rate of about a pound to the thousand cubic feet of space to be fumigated. We generally used the Dutch oven placed in a box of sand or vessel of water, so that in case of a leak, or in case of the oven’s getting too hot, the floor would not catch on fire. With a large force of ignorant men engaged in this work constant watchfulness has to be used to see that fires do not occur. The proper amount of sulphur is placed in the Dutch oven, a little alcohol poured over the sulphur, and a match applied. The sulphur will burn for three or four hours, and will produce very dense fumes which will fill the building and kill all the mosquitoes. The fumes of sulphur in a building which has been well prepared will kill not only all mosquitoes, but all insect and animal life, and is by far the best material to use for this purpose. It is generally somewhat difficult to start the sulphur burning with alcohol alone, and I have noticed that the men got in the habit of using an ounce or two of pyrethrum placed on top of the sulphur for the purpose of starting the fire. The pyrethrum was moistened with the alcohol and would burn for a considerable time after the alcohol was consumed, in almost every instance starting the sulphur burning. The fumes of sulphur will tarnish gilt metals of all kinds, and injure most light-colored fabrics. This occurs particularly where the air is heavily charged with moisture. In cases in which sulphur was likely to do damage, we used pyrethrum powder. This powder does not tarnish or injure fabrics of any kind. The building must be prepared in the same way as for sulphur, and the vessel in which the pyrethrum is burned must be arranged as above described for sulphur. The fumes of pyrethrum do not generally kill the mosquito, but simply intoxicate her. In the course of time she revives and eventually entirely recovers. For this reason the building should be opened up within a couple of hours after the burning of the pyrethrum, and all mosquitoes carefully gathered and burned.