SPOROZOA 1103 



only the pigmented trophozoite, but also the crescentic gametocytes and 

 flagellating microgametes, and, because of the activity of the flagella, 

 called the parasite Oscillaria malaria, a name afterwards given up. 

 Later, in 1885, Celli and Marchifava described the parasite with 

 greater accuracy and named it Plasmodium malarias, a poor name, 

 since it describes merely a condition assumed by some fungi and 

 mycetozoa, yet, according to the rules of zoological nomenclature, it 

 must stand. In the same year, Golgi described the quartan parasite 

 and in the following year demonstrated the relation of the various 

 stages of the life,cycle of the tertian parasite to the temperature .curve. 



Even in antiquity many had noted the curious distribution of 

 malaria, and its intimate relation to swamps and marshy places. 

 Manson, who had already shown the role played by an infected mos- 

 quito in transmitting filarial disease, in 1894, suggested that the 

 epidemiology of the disease could best be explained by the hypothesis 

 that it was conveyed by the bite of some blood-sucking insect, probably 

 the mosquito. 



For years the interpretation of the flagella was a subject of con- 

 troversy. They were regarded as degeneration products by some and 

 as living elements by others. In 1897, MacCallum, working with 

 halteridium, was able to show that they were, in fact, spermatozoa, as 

 he saw them penetrate and fertilize the macrogametes, or large 

 spherical forms without flagella. 



In 1897, Ross, of the British- Indian Medical Service, described the 

 beginning of the sporogenous cycle in what he called a dapple-winged 

 mosquito, which we now recognize as an anopheline. Following out 

 further Manson 's hypothesis, he was able the same year after long and 

 laborious research to clear up the method of transmission of bird 

 malaria, proteosoma, an analogous disease. Grassi and Bignami and 

 Bastianelli, in 1898, succeeded in demonstrating the complete life 

 cycle of the human form of malaria in the anopheles mosquito. 



Geographical Distribution. The disease is found in a belt round 

 the world extending from 40 degrees S. latitude to 60 degrees N. ; it is, 

 however, not equally distributed throughout this zone, and even in the 

 tropics there are many malaria-free areas, principally in the regions 

 of higher altitudes, since the special home of malaria is in the low- 

 lying, swampy and torrid coastal districts and river basins. Islands 

 at a distance from the main land may be entirely free. Malaria 

 reaches its maximum intensity in the tropics, where the anopheline 

 mosquitoes breed continuously throughout the year- and new infec- 



