460 



grounds or water of animals and fishes which are natural enemiefe' 

 of mosquito larvae. To the presence of a small fish called 

 ^' millions " in the ponds of Barbados has been attributed the 

 absence of malaria from that island. 



Modern science has shown that nearly all diseases, directly 

 or indirectly, are caused by germs. In many cases these 

 germs have been discovered ; in others they are yet to be 

 found. In the majority of cases, disease germs are parasites, 

 and therefore, to keep in existence, these species require to 

 pass from host to host. Many require for their transmission 

 from one individual to another the services of a third and 

 entirely different animal. Whatever may have been the 

 original source of the pathogenic parasites of man, it is certain 

 that many which have a wide distribution at present were 

 much more restricted originally. There is yet one factor which 

 undoubtedly has contributed powerfully to delay the diff'usion of 

 certain protozoal Tropical diseases. It has been mentioned that 

 most of these depend on definite animal intermediaries for their 

 transmission. Although this necessity has undoubtedly operated 

 powerfully against the spread of certain Tropical diseases, there 

 is reason to believe that in time this difficulty will disappear.- 

 Two years ago the Entomological Research Committee for 

 Tropical Africa was formed under the auspices of the Colonial 

 Office (August 26, 1909). It consists of twenty members, 

 including Sir David Bruce, Sir Patrick Manson and Sir John 

 Macfadyean. All officers proceeding to take up appointments in 

 Tropical African colonies now receive a short course of instruction 

 in the fundamental principles underlying " Insects and Disease," 

 and, as a consequence, many of these, by collecting and observing, 

 have greatly added to the sum of our knowledge. The telling of 

 this story is short and simple enough ; but the hardships and 

 difficulties encountered by the early pioneers must ever remain a 

 sealed book. Many sacrifices have already been laid down on the 

 altars of science ; several brilliant investigators have succumbed 

 to the subtle diseases whose secrets they have helped to elucidate 

 silent heroes whose names will never cease to live in the roll of 

 the martyrs of science. 



Dr. Simpson then exhibited a number of interesting lantern 

 slides, photographs of some of the insects referred to, and of the 

 type of country in Gambia where the tsetse is found, other views- 



