266 THE FARMER'S VETERINARIAN 



advanced, coughing and perhaps difficult breathing. 

 If the disease is in the liver, it cannot be readily 

 distinguished until it is far advanced. If the dis- 

 ease is in the udder it manifests itself usually by 

 the organ becoming firm or hard, and when the 

 tissues are sufficiently broken down the milk from 

 that quarter will be changed in appearance; some- 

 times it is thick, containing pus, sometimes thin 

 and watery. It is very difficult to diagnose tuber- 

 culosis from the symptoms, as many other causes 

 may give rise to similar manifestations. 



As tuberculosis is caused by a specific germ, the 

 disease is spread by the germs escaping from the 

 diseased animals and getting into the bodies of 

 healthy ones. The tubercle bacteria escape from 

 the infected animal with some one or more of the 

 natural discharges of the body. For example, if 

 the cow has a bad tuberculous area in the lung, the 

 bacteria may be discharged into one of the air tubes 

 and coughed up into the mouth. Some of them 

 will escape with the saliva and infect mangers or 

 pastures. Some of them may be swallowed and 

 escape from the body with the feces. If the dis- 

 ease is in the udder the germs will escape with the 

 milk. There are some observations which indicate 

 that sometimes the bacteria will escape with the 

 milk where the udder is not affected. After the 

 bacteria leave the diseased animal and are left in 

 the manger, or in the pasture, or on the surface of 

 water in the drinking trough, they can be readily 

 taken up by healthy cattle that eat or drink after 

 them. If they escape with the milk, calves and 

 pigs that are fed with it readily become infected. 

 After the germs get into the body of the healthy 

 animal they will multiply and produce the disease, 

 just as the seed of a noxious weed will, if blown 



