CHAPTER XXVII 

 TUBERCULOSIS 



TuBEKCULOsis IS a contagious and infectious disease of man 

 and domestic animals, affecting any body tissues, but esi)ecially 

 the lymphatic glands and lungs. The characteristic diseased 

 change in the tissues is the fonnation of the tubercle or nodule. 



History. — Tuberculosis is one of the oldest of known diseases 

 of domestic animals and man. Its contagious and infectious char- 

 acter was proven by Villeniin in 1S05, who by experimental in- 

 fection transmitted tuberculosis from 

 man to animals and from animal to 

 animal. It was in 1882 that Dr. Rob- 

 ert Koch discovered and proved by in- 

 oculation experiments that the disease 

 was caused by a specitic genu (Fig. 

 88). Prior to the experiments by Ville- 

 min and Koch, the belief was that tuber- 

 culosis was due to heredity, unsanitary 

 conditions and inbreeding. Following ^^°- ss.— Koch's Badiius tuber- 



culosis. 



discovery of the specific germ and con- 

 ditions favoring its development and sjiread, numerous scientifi- 

 cally conducted experiments were made. These have resulted in 

 practical methods of control and elimination of tuberculosis from 

 herds having tliis disease. By carefully conducted experi- 

 ments and other forms of educational work the infectious charac- 

 ter of tuberculosis and the economic importance of preventive 

 measures have been demonstrated. The average stockman 

 is well informed regarding the character and economic impor- 

 tance of this disease, but there is no general application of this 

 knowledge, and tuberculosis is increasing in dairy and breeding 

 herds. The slow development of tuberculosis, and tlie absence of 



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