198 BACTERIA 



bacilli of the human type. The bovine type of bacillus differs 

 from the human in the following ways: 



1. It is much more pathogenic for guinea pigs and rabbits. 



2. It produces more extensive lesions in cattle. 



3. It is shorter than the human. . 



4. It produces more alkali in acid media. 



5. It is more readily isolated from original lesions and does not 

 demand animal juices in culture media so emphatically. 



The subject of the infectiousness of bovine tuberculosis for 

 man has lately been exhaustively studied by Park and Krumwiede. 

 Their conclusions are that bovine tuberculosis is practically a 

 neglible factor in adults. It very rarely causes pulmonary tuber- 

 culosis or phthisis, which disease causes the vast majority of deaths 

 from tuberculosis in man, and is the type of disease responsible for 

 the spread of virus from man to man. In children, however, the 

 bovine type of tubercle bacillus causes a marked percentage of 

 cases of cervical adenitis leading to operation, temporary disable- 

 ment, discomfort and disfigurement. It causes a large percentage 

 of the rarer types of alimentary tuberculosis requiring operative 

 interference or causing the death of the child directly or as a con- 

 tributing cause in other diseases. In young children it becomes a 

 menace to life and causes from 6J to 10 percent of the total fatal- 

 ities from this disease. 



It is not always easy to differentiate the tubercle bacillus from 

 other pathogenic and comparatively harmless acid-fast bacilli. 

 Among these are the B. lepra, the B. smegmatis, and a number of 

 organisms found in butter, milk, hay, grass, and in the blind 

 worm. Culturally, the difference is great. "Tuberculins" (using 

 the term as a convenience to describe extracts of cultures), of the 

 different acid-fast bacilli, if injected into animals already infected 

 with the same type of organism from which the extract was made, 

 cause the animal to react toward the "tuberculin." If a tuber- 

 cular cow was injected with a "tuberculin" of a grass bacillus, 

 no reaction would occur, while a tubercle bacillus "tuberculin" 



