466 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 84 



Trypanosome of sleeping sickness, the Leishman bodies of kala- 

 azar, the Spirochaete of syphiHs, and others. 



The first discovery which impHcated insects as carriers was the 

 finding by Sir Patrick Manson in 1879 of the role of the mosquito, 

 Culex fatigans, in the development and carriage of filarial worms. 

 The second was the discovery by Theobald Smith in 1889 to 1891 of 

 the carriage of the causative microorganism of Texas fever of cattle 

 by a tick. The third was the discovery by Sir (then Major) Ronald 

 Ross in 1898 of the carriage of malaria by Anopheles mosquitoes. 

 The fourth was that by Reed, Carroll, Lazear, and Agramonte of the 

 carriage of yellow fever by the mosquito, Acdes acgypti (then known 

 as Stegomyia fasciata). The fifth was the discovery by Graham in 

 Syria that dengue fever is carried by mosquitoes. Then followed the 

 discoveries of the carriage of certain spirochaete diseases by ticks, the 

 carriage of a fatal disease of cattle in Africa by tsetse flies, and the 

 carriage of sleeping sickness in Africa by tsetse flies. 



In all of these diseases, insects or ticks were found to be necessary 

 secondary hosts of the parasitic organisms, but along with these dis- 

 coveries were others in which insects were shown to be mechanical 

 carriers of disease. Among these were the carriage of bubonic plague 

 by fleas, typhoid or enteric fever by the house fly, typhus fever by 

 lice, and so on. 



Practically all of these discoveries were made by medical men, but 

 they indicated in a most striking way the value of entomological knowl- 

 edge. They gave an entirely new aspect to the study of entomology, 

 and it is not to be wondered at that the skilled entomologists at 

 once turned their attention to the groups of insects that were involved. 

 At first the medical men seemed to feel that entomology was after all 

 a rather simple thing and that it would be easy for them to handle the 

 whole field thus developed. But it has become obvious that to secure 

 the best results men trained in economic entomology and broadly 

 trained in the biology of insects are of the utmost importance. One 

 way to control the disease is to control the insect that carries it ; hence, 

 men trained in the control of insects are the ones to do the work to 

 best advantage. 



The greater importance of insect-borne diseases in the Tropics was 

 early recognized, and England's great colonial possessions justified 

 and in fact necessitated the founding of the great schools of tropical 

 medicine at Liverpool and London. A similar school was founded 

 later at Hamburg by the German Govermnent, but the loss of her 

 tropical possessions has minimized the later work at this institution. 



