5 so BOVINE TUBERCULOSIS. 



Cattle should not be placed so that their heads are close together; 

 each animal should have plenty of room and occupy the same place in 

 the stable at all times. These precautions will prevent the nasal, lung, 

 or vaginal discharges from one animal striking the head or soiling the 

 feed of another. It is true that it is impossible to prevent animals 

 licking each other outside of the stable, but it should be remembered 

 that prevention must begin with the removal of all cases which are 

 suspected of discharging tubercle bacilli. Stables should, furthermore, 

 be carefully protected from the expectorations of human beings affected with 

 (consumption^ tuberculosis of the lungs. 



In endeavoring to comprehend the peculiar nature of this disease 

 bear in mind that the virus, i. e., the tubercle bacilli, do not live and 

 multiply in the blood. They are simply carried in the blood, in 

 advanced cases, from organ to organ, and speedily fixed in the tissues, 

 where they produce fresh crops of tubercles. In the earlier stages, 

 when single glands only are the seat of the disease, the blood is free 

 from infection. This accounts for the immunity of the milk in these 

 stages. If there were any method of distinguishing these cases the 

 danger incident to the milk supply could be easily removed. In prac- 

 tice, however, no such distinction can be definitely made; hence the 

 suspicion which rests on all milk which comes from infected herds. 



Tuberculosis thus differs from other infectious diseases not so much 

 in its nature as in the degree of its activity. It is a disease long drawn 

 out, presenting stages, covering months and years, the duration of 

 which in other more rapid diseases is measured by days. 



THE CONTAGIOUSNESS OF THE DISEASE. 



This is linked to the tubercle, bacillus, for without it tuberculosis 

 cannot develop. Hence our knowledge of the transmission of the dis- 

 ease is derived largely from what v/e know of the life history of the 

 tubercle bacillus within and without the animal body. Tubercle bacilli 

 may pass from diseased animals in the following ways: 



(i) In discharges coughed up, in the case of advanced disease of the 

 lungs. When the glands of the throat are diseased, they may, after a 

 time, break down and discharge into the throat. Other glands about 

 the head and neck may discharge directly outward. 



(2) In discharges from bowels, in advanced stages. 



(3) In discharges from vagina, in case of tuberculosis of the uterus. 



(4) In milk, when the udder is tuberculous or the disease generalized. 



