INFECTIOUS DISEASES 217 



to the eye. The usual outcome of ocular necrobacillosis 

 is destruction of the eye, and if both eyes are involved 

 the animal becomes blind and usually has to be destroyed. 



Necrobacillosis as a sequel of castration has been 

 previously discussed (See p. 120). 



Necrobacillosis is a disease that may affect practically 

 any and all tissues of swine and is of considerable economic 

 importance. The most common forms of the disease 

 are necrotic stomatitis and enteritis, and necrosis of the 

 sheath. 



TUBERCULOSIS 



Tuberculosis is a specific infective disease caused by 

 the tubercle bacillus and characterized by the formation 

 of tubercles. 



History. Tuberculosis has been recognized from 

 the remotest time in the history of man as a prevalent 

 disease of mankind. In 1689 the tubercle was identified 

 by Morton as the typical lesion of tuberculosis. Various 

 investigators have given additional knowledge on the 

 subject of tuberculosis. In 1865 Villemin proved the 

 infectiousness of the disease, while Koch discovered the 

 tubercle bacillus in 1882, thus establishing firmly the 

 theory of the infectiousness of tuberculosis. The study 

 of tuberculosis has been advanced and its recognition 

 clinically has been made possible by the use of tuberculin 

 which was discovered by Koch in 1890. In 1901 he 

 startled the scientific world by announcing at the tubercu- 

 losis congress in London that human and bovine tuber- 

 culosis were separate and distinct diseases, a statement 

 that was responsible for the organization of different 

 scientific bodies that, after careful investigation, reported 

 that although there may be some slight difference between 

 the tubercle of human and bovine origin, the disease 

 produced is the same and that the disease is inter- 

 transmissible between animals and man. 



Occurrence. Tuberculosis is becoming very preva- 

 lent among swine.^ This is due to the fact that the dairy- 

 ing industry is becoming- more extensive and the byprod- 



