FIFTIETH ANNUAL CONVENTION 169 



tablishing free areas. This work is, in fact, now being 

 taken up. If a county contains, say, 25,000 cattle and 250 

 of them are tuberculous, why not kill the affected ones and 

 obtain a 100 per cent healthy county? Of course one test 

 will not accomplish such a clean-up, but by a persistent ef- 

 fort a tuberculosis-free county may be attained. 



This is proved by the results of the co-operative tuber- 

 culosis-eradication work in the District of Columbia. In 

 1909 the Commissioners of the District promulgated an 

 order requiring a tuberculin test on all cattle within the 

 District and on all intended for movement into this area. 

 As a result of this co-operative work conducted by the Bu- 

 reau of Animal Industry the per cent of tuberculous cattle 

 has been reduced from 18.87 per cent in 1910 to 0.63 of 1 

 per cent in 1919, thus establishing an area practically free 

 from the disease. If this area can be made free from the 

 cattle plague, why not all the counties in States where the 

 disease exists to a much more moderate degree than was 

 found at the beginning of the work in the District of Co- 

 lumbia? 



In time it will be possible so to reduce any area infect- 

 ed with tuberculosis in live stock that owners will find it 

 unprofitable to keep infected animals or those suspected of 

 being infected with that disease. Experience has shown 

 also that the longer diseased cattle are kept in a herd 

 the greater will be the loss when the clean-up campaign 

 begins. 



Methods of Testing. 



The methods employed by the co-operating State and 

 Federal officials include not only the application of the 

 subcutaneous tuberculin test, to be followed by the proper 

 cleaning and disinfection of the premises, but also include, 

 in special cases of badly infected herds, the application of 

 the ophthalmic and intradermal methods of tuberculin test- 

 ing. The intradermal test can be and is profitably employ- 

 ed on range cattle or others which are difficult to restrain 

 or on animals showing abnormal preliminary temperatures. 

 The ophthalmic test has proved to be especially valuable 



