CHAPTEE III. 



BACILLUS TUBERCULOSIS. 



THE Bacillus tuberculosis is the specific cause of all tuber- 

 cular processes. It is one of the most commonly occurring 

 germs, and therefore also one of the most dangerous. As 

 early as 1868 Villemin showed that tuberculosis was an 

 infectious disease, and that it might be produced experimen- 

 tally by injecting tuberculous matter into healthy animals. 

 Cohnheim later confirmed these findings, and in 1882 Robert 

 Koch discovered the tubercle bacillus and succeeded in culti- 

 vating it. 



The tubercle bacillus is found in all tubercular lesions and 

 in the sputum of patients suffering from pulmonary or laryn- 

 geal tuberculosis ; in the milk of tubercular cows ; in rooms 

 inhabited by tubercular patients (unless proper precautions 

 are taken) who are not careful as to the disposition of their 

 sputum ; in food, especially the meat of tubercular cattle ; 

 and in the milk of a tubercular mother. It may also be 

 found in the excretions of animals and persons suffering from 

 intestinal tuberculosis ; further, in all places and convey- 

 ances where tubercular persons expectorate promiscuously, 

 thus favoring desiccation of the sputum and dissemination 

 of the bacillus. 



Biology and morphology: The tubercle bacillus is a very 

 slender, rod-shaped organism, 1.5 /j. to 4 p. in length, and 

 0.2 /j. to 0.4 n wide. It has rounded ends, and frequently 

 is slightly curved. It is non-motile and has no flagella. It 

 may be seen in a variety of arrangements. Usually it occurs 

 singly ; but it may be paired or form chains of three or 

 four, especially in culture. At times the bacillus may be 

 clubbed at one end, or it may exhibit central bulging sugges- 

 tive of sporulation. This appearance of sporulation is more 



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