144 TUBERCUI^OSIS 



often becomes the seat of tubercular deposits in cases of gen- 

 eralized tuberculosis. 



When the primary infection is restricted to a single focus 

 the disease is said to be localized. \'\''hen the specific bac- 

 teria are spread from the primar}- lesion through the agencj' 

 of the l\mph and blood streams, sprinkling other organs with 

 the infecting bacteria each of which becomes the starting point 

 for the development of a new tubercle, the disease has become 

 generalized,* 



It was formerly considered that when the lesions existed 

 in both of the large (abdominal and thoracic) cavities of the 

 body the disease was generalized. It is possible, however, for 

 it to be generalized when the lesions are restricted to the 

 organs of one cavity as the secondary seeding with the bacteria 

 that have escaped from a primary focus through the circulation 

 may be restricted to the cavity in which the first lesion devel- 

 oped. It seems better, therefore, to accept Ostertag'.s views and 

 classif3' local and general tuberculosis in accordance with the 

 nature of the lesions rather than their distribution in the body. 



The fact is worthy of consideration, that ver)- often cattle 

 killed after reacting to tuberculin do not show extensive dis- 

 tribution of lesions. Frequently animals are killed soon after 

 infection has taken place, in which case the lesions are re- 

 stricted to a single lymphatic gland or other organ. In other 

 cases old lesions of considerable proportion are found as shown 

 in plate II, where the heart muscle was entirely encased in a 

 thick calcareous tubercular deposit. In this case, the animal 

 was in good flesh and killed for beef without a suspicion that 

 it was in any way diseased. 



§ 112. Tuberculosis in swine. Channels of infection. 

 It is stated that young animals belonging to the precocious 

 breeds seem to be more liable to tuberculosis than others. In 

 nine cases out of ten the animals are infected by ingestion. The 

 pig easily becomes tuberculous when fed on material rich in 

 tubercle bacteria. If pigs are fed on the refuse from dairies 

 and cheese manufactories in districts where there is much 



*The Federal meat inspection regulations state, that animals affected 

 with "extensive or generalized tuberculosis" are to be condemned. 



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