VACCINES : DIAGNOSTIC AND CURATIVE 111 



culosis-free) were tested again with avian tuberculin 

 eight months after the first test, and only 88 per cent, 

 gave a positive result. This may have been due to 

 spontaneous recovery in the interval between the tests, 

 or to a curative effect of the vaccine ; or, again, it may 

 have been due to failure on the part of the vaccine. 

 Other observers have found that an animal may give 

 quite different results within a month with the same 

 dose of avian tuberculin (vide infra). 



O. Bang recommends mixing avian tuberculin with 

 ordinary diagnostic tuberculin with the object of 

 testing for Johne's disease and tuberculosis at the 

 same time. He concludes that if an animal reacts to 

 avian tuberculin it may safely be assumed to be suffer- 

 ing from pseudo-tuberculous enteritis, but a negative 

 result would seem to be of doubtful value. 



In 1909, Le Sueur of Jersey, in conjunction with 

 O. Bang, tested 194 head of cattle with avian tuber- 

 culin, and in a private communication Le Sueur 

 writes: "With regard to the avian tuberculin test I 

 do not regard it as practical, and feel convinced that 

 the reaction which takes place after injection is simply 

 due to the large amount of tuberculin injected." In 

 the same year Malm tested with avian tuberculin two 

 calves in which the disease had been produced by 

 feeding with infected mtestine. The first animal was 

 tested subcutaneously on five occasions, with two 

 positive and three negative results. In the tests 

 that proved positive large doses were given. The 

 ophthalmic test was applied with avian tuberculin 

 three times, two reactions being positive and one 

 uncertain. Of intradermal tests one was positive and 

 two were negative. The animal was slaughtered, and 

 the diagnosis of Johne's disease confirmed by B. Bang. 

 The second calf, with avian tuberculin, gave three 



