Sanitation in Panama

by William Crawford Gorgas

One of these methods was the open ditch, such as the farmer used for the ordinary draining in agricultural work. At Panama, there were several objections to this method. While the ditch drained the surrounding ground and stopped mosquito-breeding at this point, it became a most excellent breeding-place itself, as the grass grew in the bed of the ditch. At Panama, rain fell daily for eight months of the year, and the temperature was always high enough from one year’s end to another to encourage vegetable growth. The grass, therefore, grew so rapidly that the ditch had to be cleaned out every two or three weeks. The cost of keeping open a surface drain of this kind we found to be very high.

Another system of drainage which the inspectors used very freely and found very useful, was that of filling the ditch, after it had been excavated, with broken stone. This largely prevented the growing of grass, and also prevented any development of mosquitoes in the ditch itself. Another form much resorted to was that of lining the ditch with concrete. This entirely prevented the growth of grass and did away with the expense of up-keep. The only expense involved in caring for such a ditch was that of a man going over it now and then and removing such obstructions as may have gotten in. Mr. Le Prince and his inspectors became very expert in this style of concrete work, and finally, by the use of chicken wire as a framework for strengthening the concrete, were enabled to lay a ditch of this type very cheaply. Wherever the drainage was expected to be used for a year or more, we found it more efficient and economical to use concrete rather than the open ditch.

Mr. Le Prince and his staff devised several processes whereby the cleaning of these ditches of grass was much cheapened. Several solutions of arsenic were found which, when applied to the grass, killed it. Such a process kept the grass down for a much longer time than that of simply cutting it out with a hoe. A burner was devised which atomized oil under air pressure, making a very hot flame which destroyed the grass roots.

After once clearing a piece of ground the inspector had to keep it in such condition that it would not protect adult mosquitoes. He had, therefore, not only to keep it clear of brush, but also must not allow the grass to grow more than a foot in height. For grass-cutting, there was a great economy in using the horse-mower wherever we could. Numerous open ditches interfered with the use of a horse-mower. To meet this difficulty, the inspector used sub-soil tiled drainage wherever it was feasible. This is the ideal anti-mosquito drainage. It carries off the water, so that there is no formation of breeding-places on the surface. After it is once laid it requires no work or expense for up-keep, and a horse-mower can be used just as freely over its surface as if there were no ditch there.

With the various methods just mentioned we drained pretty well about one hundred square miles of territory, constructing in all some five million feet of open ditch, some one and a half million feet of concrete ditch, some one million feet of rock-filled ditch, and about one million feet of sub-soil tile.

For doing this ditching, each inspector had a gang of men under a competent foreman. In many instances, where the work was extensive and required unusual skill, such as tile-laying, the gangs especially experienced in this work were transferred from district to district. Often it is not possible to drain—for instance, a large swamp area, or where the locality is to be occupied so short a time that it is not economical to drain. In such an extensive engineering work as was being carried out on the Isthmus, the construction work was constantly interfering with the drainage and making pools and puddles which had to be looked after. In these instances, and many others of similar character, the use of kerosine oil was our only resource. The oil was distributed from a can on a man’s back, by a pump which he worked with his hand, forcing the oil through a nozzle to the place which he wished to affect. In general, we used crude oil of commerce, not because it was the best, but because it was so cheap that we could use it much more extensively than the rectified oil. It was so thick, however, that we had to thin it with various mixtures before we could spray it through the nozzle. This cost us a fraction over two cents a gallon, and we used about fifty thousand gallons a month over the hundred square miles of territory we were treating. It is not necessary to look after all collections of water in order that mosquito-breeding may be prevented. If the water is sufficiently deep and clear of grass, so that the fish can have free access, these fish will destroy all the larvæ, and mosquitoes will not develop. But all natural collections of water in a warm climate such as Panama have grass and algæ freely growing on its edges, and these obstructions protect mosquito larvæ, particularly the larvæ of the malarial mosquito, the anopheles.

Gatun Lake, the large lake made by the damming of the Chagres River, gave us a great deal of trouble on this account during the last two years of construction. Not only would the anopheles breed freely around the edges of the lake, but wherever trees or vegetable matter were floating, there algæ grew freely and anopheles larvæ were found in abundance. We found that the anopheles larvæ on the Isthmus developed just about as freely in the mountains as they did in the lowlands. The clear mountain torrent seemed to be just as acceptable a home for the anopheles as the edge of the lowland swamp. At Panama, the temperature remains the same all the year round. The water of the mountain stream is sufficiently warm for his development, just as in the swamp. The stream, as it winds down the mountain, grows grass and algæ freely on both sides of its tortuous course, and here the larvæ of the anopheles find safe harbor. Into this grass and algæ oil will not spread. We had to find something that would dissolve in the water and poison the larvæ protected by the grass and algæ.

Dr. Samuel Darling, of the laboratory, finally worked out a mixture of carbolic acid, resin and alkali, which would emulsify in water and accomplish this purpose. The mixture was known as larvacide. The method of its manufacture was as follows:

One hundred and fifty gallons of crude carbolic acid are heated in an iron tank having a steam coil, with steam at fifty pounds pressure. Two hundred pounds of finely crushed and sifted common resin are dissolved in the heated acid, and thirty pounds of caustic soda dissolved in six gallons of water are added. There is a mechanical stirring rod attached to the tank. The product is ready in a few minutes, yielding about three and one-half barrels.

Cost of Manufacture, August, 1909.