FLIES AND TYPHOID FEVER 237 



tioning of the body, and hence may be said to be the 

 direct cause of disease. Generally speaking, however, 

 the diseases with which insects have to do are actually 

 produced by bacteria and unicellular animals. The in- 

 sect merely serves as a carrier for these lesser organisms. 

 They may attach to the hairs or the outer surface of the 

 insect's body and be carried from place to place; or .the 

 disease-producing parasite may actually live within the 

 body of the insect, and there undergo certain stages in 

 its development before being transmitted to some other 

 organism. 



Flies and Typhoid Fever. — The first of the two 

 methods whereby insects transport germs is exemplified 

 by the history of the ordinary house fly. In the course 

 of its wanderings, always on the search for decomposing 

 organic matter, it may settle upon the excreta of a dis- 

 eased patient, pick up a million or two bacteria (as has 

 been repeatedly proven) that attach to the pads of its 

 feet or elsewhere on the body,, and then alight upon food 

 or drinking and cooking utensils and dislodge thousands 

 of bacteria in the process. By this means disease germs 

 are widely distributed, and unfortunately find new 

 hosts in which to live and multiply. 



The habits of the house fly are now so well known to 

 the physician and sanitarian that he is able to prescribe 

 effective means of control. He knows that by disinfect- 

 ing the excreta of typhoid patients he can prevent the 

 fly from becoming a carrier of the disease organism. 

 Moreover by screening all animal excreta, where the flies 

 breed, he can greatly reduce the number of flies. By 

 " swat the fly " campaigns he can still further reduce 

 their numbers, especially if this be >done late in the 

 season. Then by insisting on having all foods screened 

 or otherwise protected from flies he prevents the few that 

 remain from doing serious harm. 



Flies and Sleeping Sickness. — Through the me- 

 dium of the press much publicity has been given to sleep- 



