THE TUBERCULIN TEST OF CATTLE FOR TUBERCULOSIS. 855 



diagnosis are included among two classes of cattle. The first class con- 

 tains those that are tuberculous, but which do not react either because 

 of the slight effect of an ordinary-sized dose of tuberculin on an advanced 

 case of the disease with so much natural tuberculin already in the sys- 

 tem, or on account of a previous test with tuberculin which produces 

 a tolerance to this material lasting for about six wrecks. The second class 

 includes those that are not tuberculous, but which show an elevation of 

 temperature as a result of (a) advanced pregnancy; (6) the excitement 

 of oestrum; (c) concurrent diseases, as inflammation of the lungs, intes- 

 tines, uterus, udder, or other parts, abortion, retention of afterbirth, 

 indigestion, etc.; (d) inclosure in a hot, stuffy stable, especially in sum- 

 mer, or exposure to cold drafts or rains; or (e) any change in the method 

 of feeding, watering, or stabling of the animal during the test. 



Notwithstanding all these possibilities of error, the results of thousands 

 of tests show that in less than 3 per sent of the cases tested do these 

 failures actually occur. In the first class the chances of error are de- 

 cidedly reduced by the skilled veterinarian by making careful physical 

 examination and diagnosing these advanced cases, and by the injection 

 of double or triple doses into all recently tested cattle, with the taking 

 of the after temperatures beginning two hours following the injection 

 and continuing hourly for twenty hours. In the second class errors are 

 avoided by eliminating those cases from the test that are nearing parturi- 

 tion or are in heat, or show evidence of the previously mentioned dis- 

 eases, or exhibit temperatures sufficiently high to make them unreliable 

 for use as normal. Then, in reading after temperatures it is advisable 

 not to recognize as a reaction an elevation of temperature less than 2° F., 

 or one which at the same time does not go above 103.8° F., and the tem- 

 perature reaction must likewise have the characteristic rainbow curve. 

 (Those cases which approximate but do not reach this standard should be 

 considered as suspicious and held for a retest six weeks later.) In addi- 

 tion, a satisfactory tuberculin must be used, also an accurate thermom- 

 eter and a reliable syringe in order that a sufficient dose of tuberculin 

 may be given. Finally, the number of apparent errors of the tuberculin 

 test will be greatly diminished if a careful post-mortem examination is 

 made, giving special attention to the lymph glands. 



This low percentage of failures being the case, cattle owners should 

 welcome the tuberculin test not only for their own interest, but for the 

 welfare of the public as well. Where this method of diagnosing the 

 disease has been adopted tuberculosis is gradually being eradicated, while 

 it is spreading rapidly and becoming widely disseminated in those dis- 

 tricts where the tuberculin test has not been employed. Without its 

 use the disease can not be controlled, and the cattle owner is confronted 

 with serious and continuous losses; with its use the disease can be erad- 



