206 



they closed in. Behind them thorough rat proofing was carried out. 

 One section after another was treated in this way tmtil they had all 

 been wiped out. Once weeldy thereafter rats were caught in the pre- 

 viously infected sections and at other places which were insanitary and 

 which had been infected in years gone by. This was continued for 

 one year. 



The city was then divided as is shown in the diagram facing this 

 page, and rats are caught once weekly at each point at which the 

 lines intersect and sent to the laboratory for examination. 



In addition, sanitary inspectors are instructed to bring in dead rats 



Fig. 59. — Isolated plague-infested center, Manila, P. I. 



which have evidently died of disease, and more detailed rat catchings 

 are made along the water front. 



It is understood of course that rat proofing of the entire city 

 should be thoroughly carried out and constantly maintained. 



CONCLUSIONS. 



1. Since the above system was adopted plague has disappeared in 

 the city of Manila; among human beings in 1906; among rats in 19G7, 

 and it has not reappeared since. 



2. That the cost is only a small fraction of that of general rat 

 extermination. 



3. That the plan is thoroughly practical for any kind of a city. 



