CHAPTEE XI 



THE ETIOLOGY OF TROPICAL DISEASES 



Malaria : Forms of Malarial Fever, the Mosquito Theory, Prevention of Malaria — 

 Cholera: Methods of Diagnosis^Plague : Symptoms, Rats and Plague, 

 Bacteriology, Administrative Considerations — Leprosy — Yellow Fever — 

 Malta Fever — Sleeping Sickness — Beri-beri. 



It is now generally accepted that the future prosperity of the Anglo- 

 Saxon race depends upon the measure to which it is able to control 

 the Tropics. For it is obvious that that great middle band of the globe 

 which we term the Tropics is increasingly one of the most valuable 

 and important areas for colonisation in the world. Yet, though the 

 rewards are great, the risks and penalties are also great. The 

 coloniser from temperate regions knows this to his cost. Malaria 

 and plague and cholera, to speak of no other tropical diseases, have 

 made irretrievable claims upon him. Eecently it has come to be 

 recognised that much of this great loss is preventable, and ought 

 therefore to be prevented. The establishment of Schools of Tropical 

 Medicine in London, Liverpool, and other places, and the practical 

 means adopted for preventing cholera epidemics and stamping out 

 plague and malaria, are examples of the new sense of responsibility 

 which is stimulating nations and governments to do their utmost 

 to bring under control those scourges of pestilence, which have made 

 the Tropics so often the grave of the white man. 



The channels of infection in tropical diseases are various. 

 Unhealthy surroundings, diet, the soil, bad water, and parasite 

 hosts (as, for example, rats in plague and mosquitoes in malaria), 

 seem to be the chief. But there is much yet to be done in the 

 investigation of the causes of certain tropical diseases. 



We may now enter upon the consideration of five typical diseases 

 mostly limited to the Tropics : (1) Malaria ; (2) Cholera ; (3) Plague ; 

 (4) Leprosy ; (5) Yellow Fever. It is apparent that many bacterial 



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