256 



MALARIA 



To complete the cycle, the parasites return to 

 swine from human offal ; so that they propagate 

 alternately from men to swine, and from swine to 

 men. The blood-parasites which cause the deadly 

 tsetse-fly disease among cattle in South Africa are 

 transferred from one ox to another on the proboscis 

 of the ox-biting tsetse-fly. The progeny of the 

 flukes of sheep enter a kind of snail, which spread 

 the parasites upon grass. The progeny of the 

 guinea-worm of man enter a water flea. The 

 progeny of the parasites which cause Texas cattle- 

 fever, and which are very like the malarial parasites, 

 live in cattle-ticks, and are transferred by the young 

 of these ticks into healthy cattle." (Ross, Malarial 

 Fever, 1902.) 



It has further been discovered, that of the many 

 species of mosquitoes or gnats, Anopheles is the go- 

 between of malaria, and Culex of yellow fever and 

 filariasis. For want of space here, the facts relating 

 to filariasis must be left out. They are given in 

 Manson's Tropical Diseases (second edition, 1900), 

 and in the reports of the Nigerian Expedition of 

 the Liverpool School (1901). 



1. Malaria. 



The Plasmodium malaria was discovered by 

 Laveran in 1880, in the blood of malarial patients. 

 For many years his work stopped there, because it 

 was impossible to find the Plasmodium in animals : 

 "the difficulties surrounding the subject were so 

 great that this discovery seemed to be almost 

 hopeless." In 1894, Dr Patrick Manson — who had 

 proved mosquitoes to be the intermediate host in the 



