96 PRACTICAL ZOOLOGY 



on the blackboards in the schools for information as to the 

 progress of the competition, and great enthusiasm was stirred 

 up. In addition to these measures, a course of stereopticon 

 lectures was arranged, which the pupils attended in groups of 

 about one thousand. 



The result of this work, it is pleasing to say, was a decided 

 diminution of mosquitoes in San Antonio. There was some 

 opposition from the people, but on the whole the movement was 

 very popular. One result of this work was that, whereas pre- 

 viously there had been from fifty to sixty deaths a year from ma- 

 laria, this mortality was reduced seventy-five per cent the first 

 year after the work was begun, and in the second year it was 

 entirely eliminated from the mortality records of San Antonio. 



In organizing community work against mosquitoes, the school 

 children hereafter must be counted upon as a most important 

 factor. Almost every child is a born naturalist, and interest in 

 such things comes to children more readily than anything else 

 outside of the necessities of life. They are quick-witted, wonder- 

 fully quick-sighted, and as finders out of breeding places they 

 usually cannot be approached except by adults of special train- 

 ing. One of the first steps that a community should take is, 

 therefore, to arouse the interest of the children in the public 

 schools (Howard). 



Mosquitoes and Other Diseases. — There are many other 

 tropical diseases caused by minute living things that are probably 

 transmitted by mosquitoes, although we have yet to learn how 

 guilty these insects really are. A great many scientists are now 

 employed in the study of these diseases and we may hope that 

 as a result of their studies the tropics in the near future will be 

 as healthful as any other part of the world. The cause of dengue 

 or breakbone fever is not known, although it is supposed to be a 

 germ similar to those present in malaria and yellow fever. 

 Whatever it is, it is known to be transmitted by mosquitoes. 

 Elephantiasis is a disease caused by minute worms (see Chap. 

 XX) which occur in vast numbers in the blood of human 



