DISEASES OF CATTLE 345 



healthy cattle. In case the germs escape in the milk, whatever 

 feeds upon it is liable to infection. The length of time that 

 will pass after infection and before the disease visibly appears 

 varies widely, even to months or years. The length of time 

 the animal may possess the disease varies equally as much. 

 With some it may prove fatal in a few months; others may 

 carry it for years. 



The tuberculin test. — Often it is not possible to tell by a phys- 

 ical examination which animals are infected with tuberculosis 

 and which are not. The most accurate means of detecting the 

 disease in cattle is by noting the temperature of the animal 

 following the injection of a small amount of tuberculin be- 

 neath the skin. The tuberculin is prepared by sterilizing, 

 filtering, and concentrating the liquids in which the tubercle 

 bacillus has been allowed to grow. It contains the cooked 

 products of the growth of these germs, but not the germs them- 

 selves. Hence when this liquid is injected under the skin of 

 cattle, it is absolutely unable to produce the disease, but it sets 

 up a characteristic reaction or symptoms. 



Any inteUigent owner of cattle, who will make a little effort 

 to familiarize himself with the test and its limitations, can use 

 it on his own cattle with safe results. It does not require 

 the trained veterinarian. The operator must, however, be 

 familiar with the method, be very careful, painstaking, and 

 patient. 



The testing outfit. — The testing outfit consists of five things : 

 (1) tuberculin, (2) syringe, (3) thermometer, (4) disinfectant, 

 (5) vaseline. 



1. Tubercuhn. — Tubercuhn can be procured from the ex- 

 periment stations in the various states. If the Experiment 

 Station fails to provide it, the Bureau of Animal Industry, Wash- 

 ington, D.C., can tell where to secure it. 



2. Syringe. — A hypodermic syringe of 6 c.c. to 10 c.c. 

 capacity, such as is commonly used to inject liquid vaccine, is 



