426 DISEASES OF CATTLE. 



contains those that are tuberculous, but which do not react either be- 

 cause 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 system, or on account of a recent previous test with 

 tuberculin which produces a tolerance to this material lasting for 

 about six weeks. The second class includes those that are not tuber- 

 culous, but which show an elevation of temperature as a result of 

 (a) advanced pregnancy, (b) the excitement of cestnim, (c) concur- 

 rent diseases, as inflammation of the lungs, intestines, uterus, udder, 

 or other parts, abortion, retention of afterbirth, indigestion, etc., 

 (d) inclosure in a hot, stuffy stable, especially in smnmer, or exposure 

 to cold drafts or rains, (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 cent of the cases tested do these failures actu- 

 ally occur. In the first class the chances of error are decidedly 

 reduced by the skilled veterinarian by making careful physical ex- 

 amination and diagnosing clinically these advanced cases, and by the 

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

 the taking of the after temperature, beginning two hours follow- 

 ing the injection and continuing hourly for 20 hours. 



It is therefore apparent that tuberculin should be applied only by 

 or under the direction of a competent veterinarian, capable not only 

 of injecting the tuberculin but also of interpreting the results, and 

 particularly of picking out all clinical cases by physical examination. 

 The latter observation is extremely important and should always be 

 made on every animal tested. 



In the second class errors are avoided by eliminating those cases 

 from the test that are nearing parturition or are in heat or show evi- 

 dence of the previously mentioned diseases 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. and which at the 

 same time must go above 103.8° F., and the temperature reaction 

 must likewise have the characteristic rainbow curve. (Those cases 

 which approximate but do not reach this standard should be con- 

 sidered as suspicious and held for a retest six weeks later.) In 

 addition, a satisfactory tuberculin must be used, also an accurate ther- 

 mometer anjd 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 especial 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 



