3/0 AGRICULTURAL BACTERIOLOGY. 



This last fact forms at once the strength and the weakness 

 of the tuberculin test. Tuberculin does pick out with great 

 accuracy all mild cases, arid clinical symptoms will pick out 

 the rest. But this test fails to distinguish between severe and 

 mild forms, putting in one class the animal that may have a 

 small tuberculous gland, which could be healed in a short time, 

 and the animal with a severe case of intestinal tuberculosis 

 which is scattering bacilli, to the great danger of the rest of 

 the herd. Experience has shown that, of the animals respond- 

 ing to the test, some run down rapidly and require slaughtering 

 in a few weeks, while others wholly recover, live several years 

 of useful life, and after death show, by post-mortem examina- 

 tions, that the original tubercle has been healed and the ani- 

 mals have come again into normal condition. There is thus 

 a great difference between clinical tuberculosis and tuberculin 

 tuberculosis. The former results practically always in the death 

 of the animal, the latter may be temporary and insignificant. 

 The former certainly is y and the latter may or may not be, a 

 source of danger to the herd. 



In the enthusiasm which followed this easy means of detec- 

 tion, it was claimed that it might be possible to eradicate 

 tuberculosis completely from our herds, and some States started 

 upon a sweeping plan of testing all cattle and slaughtering 

 immediately all animals that responded to the test. This re- 

 sulted in the slaughter of large numbers of very valuable cows 

 which were so slightly affected that their owners rightly be- 

 lieved that they could properly have been retained for further 

 use. A violent opposition was developed at once, which soon 

 forced an entire change of the laws, but not before there had 

 arisen a great prejudice against the use of tuberculin, which has 

 not yet disappeared. This prejudice was based upon the be- 

 lief that it was a useless waste to slaughter all animals that 

 responded to this test. That belief was certainly well founded 

 and, to-day, no one will be found who will advocate such radi- 



