FARM ANIMALS 139 



In Arizona as well as in Queensland and New 

 Zealand branding fluids have been tested on a small 

 scale. It has been found that although the brands 

 were legible at first the design gradually became 

 less conspicuous and when the animal was killed 

 and the hide tanned the leather was found to be 

 injured to about the same extent as after branding 

 with a hot iron. 



DISEASES 



Tuberculosis. Among the various diseases which 

 affect cattle tuberculosis is by far the most impor- 

 tant. This disease attacks not only cattle but also 

 all other domestic animals including poultry and 

 man as well. The disease is caused by the tubercle 

 bacillus, which gains entrance to the alimentary 

 tract in the feed or to the lungs in impure air. The 

 percentage of infection increases with the age of 

 cattle. Thus in calves only a small part are in- 

 fected while in old dairy cows from 15 to 60 or 

 even 90 per cent, of the animals in individual herds 

 are affected with this disease. Tuberculosis ap- 

 pears in the lungs or all of the lymphatic glands of 

 the body, upon the vital organs and even the skin. 

 The progress of the disease may be rapid or slow. 

 The disease, therefore, may at once become appar- 

 ent or may be hidden for years. The tubercle bacilli 

 are rarely found in the meat even in advanced cases 

 of tuberculosis. The milk of tuberculous animals 

 is, however, always dangerous and should never 

 be used without previous sterilization by heating. 



A long and bitter controversy has raged over the 

 identity of human and bovine tuberculosis. It has 

 finally been demonstrated beyond question, how- 

 ever, even to the disciples of Koch, that cattle may 



