THE ACID FAST GKOUP 381 



open tuberculosis the organisms are being thrown off more 

 or less constantly by the body. In the closed type, the bac- 

 teria are not leaving the body and the disease is in this 

 condition, noncontagious. 



Cattle are probably most commonly infected by ingestion, 

 perhaps occasionally by inhalation. Hogs generally show 

 tuberculosis when they are following tubercular cattle and 

 infection is undoubtedly by ingestion. The same apparently 

 is true of tuberculosis in fowls. 



Transmission of Bovine Tuberculosis to Man. It has 

 been noted that the bovine and human tubercle bacilli are 

 relatively distinct varieties, and that the human tubercle 

 bacilli do not readily infect cattle. The conclusion was 

 reached by some investigators, therefore, that bovine 

 tubercle bacilli do not affect man. In recent years, how- 

 ever, it has been shown that in certain types of cases, and 

 particularly in children, bovine tubercle bacilli produce a 

 considerable proportion of the cases. Evidently tubercu- 

 losis can be transmitted to man, therefore, by milk from 

 tuberculous cows. The chart given on page 380 adapted 

 from Park and Krumweide summarizes the types of 

 tubercle bacillus producing disease in man in 1511 cases. 

 An examination of this table would seem to prove quite 

 conclusively that the tuberculosis of bovine origin is fre- 

 quent enough in children under sixteen years to justify 

 all reasonable precaution against the ingestion of infected 

 meat and milk. On the other hand, the bovine tubercle 

 bacillus is very rare as a cause of disease in adults. 



MYCOBACTERIUM PARATUBERCULOSIS 



Synonyms. Bacillus paratuberculosis and Bacillus of 

 Johne's disease. 



This organism is the cause of a peculiar chronic dysentery 

 in cattle. The early investigators concluded the organism 



