352 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



science of protozoology are the practical applications of protozoan 

 research. 



The working up of the malaria case against Plasmodium and 

 Anopheles reads like a Sherlock Holmes detective story. In 

 remote lands investigators of divers nationalities collected their 

 bits of evidence, which have finally been fitted together into an 

 argument of unimpeachable completeness. In 1880 the malarial 

 parasite was discovered and studied in Algiers by a French army 

 surgeon, Laveran, who correctly and unhesitatingly (albeit with 

 very inconclusive evidence) affirmed its causal relation to the 

 disease. As early as 1883 the transfer of malaria by mosquitoes 

 was suggested by King in America, and strongly argued on the 

 basis of the parallel in the occurrence of mosquitoes and malaria. 

 At the time of the establishment of the Academy the problem 

 had not been advanced materially toward a settlement ; suspicions 

 were increasing, but the verdict was still "not proven". In 1893 

 Smith and Kilbourne demonstrated the transfer of Texas fever 

 of cattle by ticks of the genus Boophilus, giving further ground 

 for the suspicion of a similar infection in malaria. Later work 

 by McCallum in America and by Ross in India on a malaria- 

 like disease of birds, and by Ross on human malaria as well, 

 led up to the final complete proof by Grassi in Italy, 1898, that 

 malaria is produced by the sporozoan parasite observed eighteen 

 years earlier by Laveran, 'and that this parasite is transferred 

 from host to host by mosquitoes of the genus Anopheles. Fur- 

 ther work by Grassi and Schaudinn has left no obscure point in 

 the complicated life history of Plasmodium, with its double re- 

 productive cycle in man and mosquito. _ The disease has been 

 repeatedly produced experimentally by the bite of infected mos- 

 quitoes ; and the wholesale protective experiments by Grassi, 

 where an entire community has been freed from malaria by pro- 

 tection against Anopheles, are hardly less conclusive. This was 

 the first demonstration of the protozoan nature of a human 

 disease. 



Perhaps more dramatic, certainly more tragic, was the in- 

 vestigation of yellow fever, a disease accredited to a protozoan 

 parasite solely on its analogy with malaria, for the actual organ- 



