=The Symptoms of Tuberculosis= vary according to the location of the disease. If it is in the glands of the throat it is suggested by their enlargement. If it is in a gland about the lungs, which, because of its enlargement, presses on the œsophagus (gullet), there might be bloating. If the disease is in the lung tissue there would be, after it is sufficiently 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 disease 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; sometimes it is thick, containing pus, sometimes thin and watery. It is very difficult to diagnose tuberculosis 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 disease 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 into a new field, germinate and produce the weed there. Tuberculosis spreads from animal to animal on the same principle that weeds spread from one field to another.