Fig. 170—Mosquitoes in resting position. (From Howard's Mosquitoes.) On left the malarial mosquito (Anopheles); on the right the harmless mosquito (Culex).
Remedies against Mosquitoes.—The natural method of preventing the spread of malaria is, of course, the destruction of mosquitoes. This is accomplished by draining pools of water where they are likely to breed, and by covering pools of water that cannot be drained with crude petroleum or kerosene. The kerosene, by destroying the larvae, prevents the development of the young. In communities where such measures have been diligently carried out, the mosquito pest has been practically eliminated. Other methods are also under investigation, such as the stocking of shallow bodies of water with varieties of fish that feed upon the mosquito larvae.
Fig. 171—Stegomyia, the yellow-fever mosquito (after Howard).
Yellow Fever.—This scourge of the tropics is, like malaria,[pg 403] caused by animal germs. It is also propagated in the same manner as malaria, but by a different variety of mosquito (Stegomyia, Fig. 171). The stamping out of yellow fever in Havana, the Panama Canal Zone, and other places, through the destruction of this variety of mosquito, affords ample proof of the correctness of the "mosquito theory."
Fig. 172—Consumption germs from the spit of one having the disease. Highly magnified and stained. (Huber's Consumption and Civilization.)
Consumption, or tuberculosis of the lungs, spoken of as the "white plague," was among the first diseases shown to be due to bacteria. Consumption is now recognized as an infectious disease, though not so readily communicated as some other diseases. Several methods are recognized by which the germs are passed from the sick to the well, the most important being as follows:
1. By personal contact of the sick with the well, especially in kissing.