vin CONQUEST OF DISEASE 231 



vigorous fight against the death-dealing mosquito, with 

 the result that yellow fever has been practically stamped 

 out. Death from yellow fever on the Isthmus of Panama 

 since 1905, when the canal zone came under the complete 

 control of the United States, is almost unknown. By 

 the destruction of a little grey gnat, a great engineering 

 enterprise was made possible of realisation. 



Wherever steady war has been waged upon the mos- 

 quito, yellow fever and malaria have practically dis- 

 appeared. Formerly, yellow fever was the constant 

 scourge of the West Indian Islands. One writer 

 says : ' The churchyards of Barbados and the other 

 islands are full of the bones of the victims ; and it is 

 said of the slopes of the Morne, in St. Lucia, that there 

 is not a square yard without the remains of a soldier 

 under it, more being there from the results of yellow 

 fever than from the bullets of the enemy." Now what 

 do we find ? The scourge which terrified the inhabitants 

 of the West Indies every year in the old days has 

 entirely vanished as the result of establishing regulations 

 dealing with the breeding-places of mosquitoes. Action 

 founded upon the word of science has converted into 

 health resorts districts in which formerly a European 

 could scarcely hope to survive. 



Malaria and yellow fever have thus been formidable 

 barriers to colonisation ; and to .have discovered their 

 cause and their remedy is of the highest importance to 

 the human race. Let us give one more instance of a 

 similar kind. In certain districts of Central and Southern 

 Africa thousands of cattle and animals die yearly of 

 what is known as fly disease. This disease is carried 

 from a sick to a healthy animal by the bite of a tsetse-fly 

 an insect only slightly larger than an ordinary house- 

 fly. Domestic animals which enter fly-districts are 



