4. By atmospheric currents malaria and mosquitoes are alike capable of being transported for considerable distances. 5. Malaria may be developed in previously healthy places by turning up the soil, as in making excavations for the foundation of houses, tracks for railroads, and beds for canals, because these operations afford breeding places for mosquitoes. 6. In proportion as countries, previously malarious, are cleared up and thickly settled, periodical fevers disappear, because swamps and pools are drained so that the mosquito cannot readily find a place suitable to deposit her eggs. 7. Malaria is most dangerous when the sun is down and the danger of exposure after sunset is greatly increased by the person exposed sleeping in the night air. Both facts are readily explicable by the mosquito malaria theory. 8. In malarial districts the use of fire, both indoors and to those who sleep out, affords a comparative security against malaria, because of the destruction of mosquitoes. 9. It is claimed that the air of cities in some way renders the poison innocuous, for, though a malarial disease may be raging outside, it does not penetrate far into the interior. We may easily conceive that mosquitoes, while invading cities during their nocturnal pilgrimages will be so far arrested by walls and houses, as well as attracted by lights in the suburbs, that many of them will in this way be prevented from penetrating "far into the interior." 10. Malarial diseases and likewise mosquitoes are most prevalent toward the latter part of summer and in the autumn. 11. Various writers have maintained that malaria is arrested by canvas curtains, gauze veils and mosquito nets and have recommended the rise of mosquito curtains, "through which malaria can seldom or never pass." It can hardly be conceived that these intercept marsh-air but they certainly do protect from mosquitoes. 12. Malaria spares no age, but it affects infants much less frequently than adults, because young infants are usually carefully housed and protected from mosquito inoculation. Correlated with the miasmatic theory was the belief that some animal or vegetable organism which lived in marshes, produced malaria, and frequent searches were made for it. Salisbury (1862) thought this causative organism to be an alga, of the genus _Palmella_; others attributed it to certain fungi or bacteria. In 1880, the French physician, Laveran, working in Algeria, discovered an amœboid organism in the blood of malarial patients and definitely established the parasitic nature of this disease. Pigmented granules had been noted by Meckel as long ago as 1847, in the spleen and blood of a patient who had died of malaria, and his observations had been repeatedly verified, but the granules had been regarded as degeneration products, and the fact that they occurred in the body of a foreign organism had been overlooked.