PROPHYLAXIS OP MALARIA. 
IS 
The selection of screening material. —The screening used for 
quarters and barracks should be of as durable material as it is 
possible to secure and of fine enough mesh to keep out all anophelines. 
The material for screening should be of wire composed of copper, 
zinc, and iron, the copper content being higher than that of brass. 
In the Tropics this is of special importance, as the heat and moisture 
rapidly corrode wire netting having a low percentage of copper. 
The observations of Nauss, in the Canal Zone, reported by Darling, 31 
proved that the deterioration of wire screening in the Tropics is due 
to the presence of iron plus the influence of a hot and moist climate. 
Brass screens, by reason of the amount of iron alloy present are, 
therefore, unsuitable, and copper-wire screens should always be 
selected. 
If copper screening can not be obtained ordinary iron-wire screens 
may be used, but they should be covered with two coats of good paint 
and frequently repainted. Even so, they will be found more ex¬ 
pensive in the end than the best copper-wire screening, which should 
be used if it can be obtained. 
The size of the mesh in the wire screening used to protect houses 
and barracks is a matter of prime importance. It must be close 
enough to keep out all anopheles mosquitoes, and in regions where 
yellow fever is endemic or may be introduced the mesh should be 
small enough to keep out the yellow-fever mosquito, Stegomyia fas- 
ciata. Nothing is gained by using a screen in which the meshes are 
closer than necessary, and something is lost, for the closer the mesh 
the more air is excluded from the room or building, and this is a 
matter of much importance, especially in the Tropics and subtropics. 
A considerable amount of experimental work has been done along 
this line. As a result of my own observations at Camp Stotsenburg, 
in the Philippines, where anophelines were very numerous, I con¬ 
cluded that wire netting containing 16 meshes to the linear inch 
(No. 16, as it is called) excluded all the Anopheles tested and that 
this size netting should be used in the prophylaxis of malaria. 32 My 
observations were confirmed, so far as Anopheles are concerned, by 
Guiteras, 33 Darling, 34 and the United States Army Board 35 for the 
Study of Tropical Diseases in the Philippines. This netting was not 
efficient, however, in excluding the yellow-fever mosquito, as the 
majority of investigators have shown, and a netting containing 18 
meshes to the linear inch should be selected when Stegomyia are 
present, as shown by the experiments of Darling and the Board for 
the Study of Tropical Diseases. 
It is very probable that mosquitoes vary in size, even when full 
grown, for Goeldi has shown that delayed development during the 
larval stage, due to various local conditions and a poor supply of 
food, results in dwarfed adult mosquitoes, and this doubtless accounts 
