122 



Insects and Disease 



support in the fact that serious outbreaks of the 

 fever often followed the coming into port of vessels 

 from the tropics with the water in their holds in an 

 offensive condition. When it was discovered that 

 bacteria were the cause of fermentation and also of 

 many diseases this theory was considered abun- 

 dantly proven. From time to time, announcements 

 have been made that the particular species of bac- 

 teria that causes the disease has been isolated, but 

 there has always been something lacking in the 

 final proof. 



Yellow fever has always been regarded as a very 

 highly contagious as well as infectious disease, and 

 the utmost precaution has been taken to isolate the 

 patients when possible and in recent years strict 

 quarantines have been established against infected 

 localities and no person or commerce or even the 

 mails were allowed to come from such places with- 

 out thorough fumigations. But all these things 

 proved unsatisfactory. The disease could not or- 

 dinarily be checked by simply isolating the patients. 

 Many people became sick without ever having been 

 near a yellow fever patient, while others worked in 

 direct daily contact with the disease and did not 

 suffer from it. Those who had once had it and re- 

 covered became practically immune, rarely suffer- 

 ing from a second attack. Negroes may suffer 



