THE TUBERCULIN TEST FOR TUBERCULOSIS 199 



sible for cattle to be so roughly handled during the test that 

 the milk flow may be seriously affected ; but this cannot be 

 charged to the tuberculin. In cases where serious results ac- 

 company or follow tuberculin tests, the disturbance usually can 

 be traced to some cause other than tuberculin. 



There are three methods of making tuberculin tests — the 

 thermal or subcutaneous, the intradermal, and the ophthalmic. 

 These may be used to good advantage in various combinations. 

 Accuracy. — Averages of very large numbers of animals tested 

 show tliat tuberculin has a high accuracy, but is not infallible. 

 Advanced cases, recently tested animals, recently infected ani- 

 mals, and certain latent and healed cases may fail to give plain 

 reaction. These are all exceptions ; in general, tuberculous 

 cattle react, and the tests are accurate enough to be thoroughly 

 practical. 



Thermal or subcutaneous test. — Any number of animals up 

 to 100 or so may be included in one test. These large numbers 

 can be handled to advantage only by one who is thoroughly 

 familiar with the test, who can use a number of thermometers, 

 and has good assistants. The injection is usually made on the 

 neck, on the flat of the rump, or beside the tail head. A veteri- 

 nary hypodermic syringe, holding 10 to 30 c.c. and provided 

 with several short and well sharpened needles is required. The 

 syringe should be first sterilized and kept clean. 



The needle should be short, of fair size, and inserted by sharp 

 push rather than a stab. Some cattle are inclined to kick. This 

 can usually be prevented if an assistant gives the tail a vigorous 

 pull sidewise at the right moment. 



Tivo periods. — The time of each test is divided into two 

 periods: (A) before, and (B) after injection. During {A) the 

 temperatures are taken e.g. at about 8 a.m., and then again at 2 

 and 4 p.m. The tuberculin is given by hypodermic injection at 

 10 P.M. During (B) the temperatures would be taken at 6, 8, 10, 

 and 12 a.m., 2, 4, and sometimes (i and 8 p.m. 



The thermometer. — Self-registering veterinary thermometers 

 are necessary for the thermal test and they slioukl be correct 

 between 100° and 105° F. Any thermometer wliich varies one 

 half degree or more from the records shown by several others 

 should be discarded. 



Temperatures are taken by inserting tlie thermometer into 

 the rectum or vagiiui, usually the former. If a number of cattle 



