INFECTIOUS DISEASES OF CATTLE. 429 



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

 accurate test of tuberculosis, that the animals which react mny 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 authori- 

 ties 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 direc- 

 tion — 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 pro- 

 tection 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, tuberculin must be considered as harmless for healthy 

 animals in view of the results revealed by numerous tests covering 

 vast numbers of animals. And it has also been clearly demonstrated 

 that tuberculin interferes in no way with the milking function in 

 healthy cattle; neither in the quantity 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 sys- 

 tem 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 

 tuberculous 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 



