426 DISEASES OF CATTLE. 



Details concerning the accredited-herd plan may be obtained by 

 applying to the Chief of the Bureau of Animal Industry, Washing- 

 ton. D. C. 



THE TUBERCULIN TESTS. 



Testing animals with tuberculin is the process of introducing 

 tuberculin into the animal and interpreting results according to well- 

 known standards. 



From the investigations and observations that have been men- 

 tioned, it may be safely concluded — 



1. That the tuberculin test is a wonderfully accurate method of 

 determining whether an animal is affected with tuberculosis. 



2. That by its use the animals diseased with tuberculosis may be 

 detected and removed from the herd, thereby eradicating the disease. 



3. That it has no injurious effect upon healthy cattle. 



4. That the comparatively small number of cattle which have 

 aborted, suffered in health, or fallen off in condition after the test 

 were either diseased before it was made or were affected by some 

 cause other than the tuberculin. 



THE SUBCUTANEOUS TEST (UNDER THE SKIN). 



The most frequently used method of testing is the subcutaneous 

 test, which consists in injecting the proper quantity of tuberculin 

 underneath the skin into the subcutaneous tissue. If an animal is 

 tuberculous, the action of the tuberculin causes a fever, which is 

 indicated by a rise in temperature. This rise, under ordinary con- 

 ditions, may occur any time between the eighth and twentieth hours 

 after the tuberculin is injected, but in some cases it is desirable to 

 measure the temperature before the eighth hour and continue to 

 the twenty-fourth hour or longer. 



The temperatures are measured at least 3 times in advance of the 

 injection, at 2-hour intervals, to learn whether the animal is in proper 

 condition to receive the test. The temperatures after injection are 

 taken every 2 hours until the test is completed. The proper inter- 

 pretation of the temperatures is made by the person applying the 

 test, and a careful observance of any clinical changes is always impor- 

 tant in determining the result. It can not be set forth too strongly 

 that the test, including the two following methods, should be at- 

 tempted only by those who are properly qualified to do the work. 



THE INTRADERMIC TEST (INTO THE SKIN). 



The intradermic test for detecting tuberculosis is used to a con- 

 siderable extent, especially in area work and on range cattle not 

 easily controlled. When made by those who have become skilled in 

 its application, it is very accurate. In this test the tuberculin is 

 injected between the layers of the skin, only a few drops being used, 

 and it is usually applied in the region at the base of the tail, where 

 the skin is soft and nearly hairless. The intradermic test is satis- 

 factory also for the diagnosis of tuberculosis in swine and, when so 

 used, the tuberculin is applied into the skin of the ear near its base. 



