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to encourage the destruction of rats in the city, and a reward of 2 

 cents Mexican money was offered for each rat brought to the health 

 department. A certain number of these rats were examined from 

 day to day from different districts. 



In August, 1901, arrangements were made by which the health 

 department collected and examined a specified number of rats 

 each day to try to determine in some degree the relative prevalence 

 of plague among these animals. This practice was continued for 

 several months, with the result that the mortality among rodents 

 from the disease was shown to have rapidly decreased until in Novem- 

 ber practically no plague-infected rats were found. 



In a discussion of the subject, furnished February 2, 1909, by Dr. 

 W. W. Pierce, medical officer of health, through Consul-General A. P. 

 Wilder, it is stated that in 1902 the fee for rats was raised to 5 cents, 

 and a special staff of coolies was engaged to destroy rats. The abuses 

 on account of these bounties were so great, however, that it was 

 found necessary to discontinue it in 1903, but the method of trapping 

 rats was continued. 



While the total number of rats taken in 1903 was 101,047, Doctor 

 Pierce stated in effect that on account of the prejudice against dis- 

 infection, it was practically impossible to secure the addresses where 

 the infected rats were found. The services of the staff were con- 

 tinued, however, until 1908, when they were abolished because it was 

 thought, as stated by Doctor Pierce, that results were not commen- 

 surate with the cost, and many complaints were heard. The plan of 

 furnishing traps to all persons who applied was then introduced, and 

 in addition, structural methods which had gone on for years were 

 continued. 



The traps were distributed through district committees consisting 

 of the more educated natives, who were informed that with their 

 assistance it would be possible to avoid abuses which had been prac- 

 ticed by the official rat-catching staff. 



Doctor Pierce stated that it had been impossible under other sys- 

 tems to secure the addresses where infected rats were found, and in 

 order to overcome this prejudice, several hundred receptacles were 

 placed in different parts of the city whereby the rats could be col- 

 lected. These tins were visited from day to day. and by this means 

 it was possible to locate infected districts. 



Doctor Pierce stated that the use of ordinary disinfectants in 

 plague-infected houses had been discontinued, and that a 2 per cent 

 mixture in water of a kerosene emulsion made by stirring warm 

 tank oil, 85 parts added gradually to 15 parts of hot, strong solution 

 of " sunlight" soap, was used. This solution .was found to instantly 

 kill fleas and bugs, and it has been used systematically. 



