422 DISEASES OF CATTLE. 



The results of a much larger number of tests might be compiled 

 at this time, but they would not materially change the average of 

 those already mentioned. It is plain that tuberculin is a remarkably 

 accurate test of tuberculosis, that the animals which react may be 

 safely considered as tuberculous, and that when a careful clinical 

 examination is practiced in addition to the test there are few animals 

 in a dangerous condition which escape detection. 



The first questions asked by those who oppose the adoption of the 

 tuberculin tests are: Is this test infallible? and, if it is not infallible, 

 why should it be forced upon the cattle owners of the country? 



In answer to these questions it may be said that tuberculin is not 

 absolutely infallible, and yet it is by far the best method of diagnos- 

 ing tuberculosis that has been discovered. It is much better than any 

 test known. for pleuropneumonia when that disease was eradicated. 



Practically all the animals that react are affected with tuberculosis 

 and should be separated from the herd, not only in the interest of 

 the public, but in the interest of the owner of the herd. The best 

 authorities admit, after studying many thousands of tests, that there 

 are few, if any, mistakes made in condemning cattle which show a 

 typical tuberculin reaction. The errors are principally in the other 

 direction — that is, some tuberculous animals are not discovered by 

 the tuberculin test, but as the most dangerous of these may be 

 picked out by ordinary clinical examination this fault of tuberculin 

 is not so serious as it at first sight appears. This being the case, it 

 should not be necessary to force the tuberculin test upon owners. 

 They should be anxious to adopt it in their own interests and for 

 the protection of their patrons. There is to-day no greater danger 

 to the cattle and hog industries than that which confronts them in 

 the form of tuberculosis, a disease already widespread and rapidly 

 extending. Furthermore, in view of the results revealed by numer* 

 ous tests covering vast numbers of animals, tuberculin must be con- 

 sidered as harmless for healthy animals. It has also been clearly 

 demonstrated that tuberculin interferes in no way with the milking 

 function in healthy cattle; neither in the quantitj^ of milk nor in 

 butter-fat value has any variation been detected. The conclusions 

 of some of the best authorities on the subject of its harmlessness to 

 healthy animals are given below. 



Nocard and Leclainche state: 



Direct experiments and observations collected by thousands show that the 

 tuberculin injections have no unfavorable effect. With healthy animals the 

 system is indifferent to the inoculation ; with tuberculous animals it causes 

 slight changes which are not at all serious. 



Bang has written as follows on this question : 



We will now consider the following question, a very important one, in the 

 application of tuberculin, viz: Can the reaction produce a worse condition in 

 tul;erculous animals than before existed? Hess emphatically states that it can, 

 and on this account he earnestly warns against its application. My attention 

 has been directed to this question from the beginning. In my first publication 



