DISEASES OF CATTLE 269 



Where is Tuberculosis Found? It is world-wide in man and 

 practically so in cattle. The native cattle in different countries 

 were originally free from it, but the introduction of the improved 

 breeds of cattle from northwestern Europe to all parts of the globe, 

 resulted in the spread of the germs of tuberculosis. 



What Determines the Distribution of Tuberculosis? The 

 germs are carried in the bodies of the diseased animals. If such 

 animals are brought into a herd, the disease spreads from these 

 to the healthy animals. Thus, the custom of buying and selling 

 stock, especially of the improved types, is one of the most potent 

 means of spreading the disease from herd to herd. Where milk 

 is produced mainly for city use, the custom of disposing of milch 

 cows when they dry off and of replacing them with fresh milkers 

 is conducive to the introduction and rapid spread of the disease 

 in the herd. A large herd is more often affected than a small 

 one, because the opportunity for introducing a diseased animal 

 into the herd is dependent on the number of animals purchased. 

 If 50 animals are purchased from 25 different herds in the older 

 dairy regions of the state, some tubercular animals are almost cer- 

 tain to be found among them. One tuberculous animal is enough 

 to start the disease in a healthy herd. 



Is One Breed of Cattle More Susceptible to Tuberculosis Than 

 Another? Cattle of any breed, beef or dairy, acquire tuberculosis 

 easily and quickly, when once brought in contact with diseased 

 animals giving off tubercle bacilli. The reasons why more dairy 

 than beef cattle have been found to be affected is because of the 

 much greater interchange; the longer period for which they are 

 retained; and the closer confinement to which they are subjected. 



What Parts of the Body may be Affected by Tuberculosis? 

 Any part of the body may be affected, but in each kind of animal 

 there are certain parts in which the disease is most likely to occur 

 in case it is present at all. 



What Parts of the Body are most Often Affected by Tubercu- 

 losis? In man the lungs are most frequently involved. In cattle 

 the parts most frequently affected are: 



1. The lymphatic glands at the base of the skull, the pharyn- 

 geal glands, which can be readily recognized when the head is re- 

 moved by the butcher. These glands will be found on either side 

 of the wind pipe and gullet close to the joint between the head and 

 the first vertebra. 2. The lymphatic glands on the wind pipe be- 

 tween the lungs, the bronchial and mediastinal glands. 3. The 

 lungs. 4. The liver. 5. The spleen, (milt). 6. The lymphatic 

 glands of the intestine, the mesenteric glands, and the membranes 

 of the abdominal cavity. 



In hogs the lymphatic glands of the neck are most frequently 

 affected, as are also the lungs and associated lymphatic glands, the 

 liver, the spleen, and the lymphatic glands of the intestines. 



What Other Parts of the Body May Be Affected? The lym- 

 phatic glands in all parts of the body may be diseased, even those 

 situated in the muscles. The brain and spinal cord are sometimes 



