THIRTY-SEVENTH ANNUAL CONVENTION. 199 



My experience is that an animal that has once showed a 

 sign of tuberculosis is a source of danger at any subsequent 

 time. That virulence of the tubercular germ is so great that 

 the animal once affected has a very slight chance of recovery. 

 Occasionally you get cases where an application of the tuberculin 

 test fails to give a positive response. That may be due to the 

 fact that the disease is being held in abeyance. I know such 

 cases as that where this latent tuberculosis has broken out again 

 so when the test was later used they responded. Where there 

 is once a reaction it becomes a ticklish matter to leave such 

 animals in your herds. 



Member: If a cow is tested and reacts, if she is inoculated 

 in from two to four weeks would she react again? 



Prof. Russell : No, that is not a sufficient length of time 

 to eliminate the tuberculin that was put in in the first time. That 

 period of time we cannot definitely fix, it varies from thirty to 

 sixty days. I should not advise retesting a herd within sixty 

 days ; after sixty days you can retest it with safety. You cannot 

 tell until then that the elimination is complete. When you ap- 

 ply a retest you use a larger dosage. 



Member: Is there any way of telling whether a cow has 

 been tested first? 



Prof. Russell : None at all. That constitutes one of the 

 most serious difficulties that we have to contend with. . There 

 are unscrupulous men in all communities that if they have a 

 tuberculosis animal, they will pump tuberculin into it before 

 they sell it. In Wisconsin we have penitentiary laws against it. 



Member : Does this tuberculin have any effect on the quali- 

 ty of milk? 



Prof. Russell : None whatever. I have drank milk during 

 the process of testing without knowing the difference. Occas- 

 ionally where you bring strangers into the barn you may get a 



