310 SPECIFIC MICRO-ORGANISMS 



recognizable occurs, or just below this amount, the general pur- 

 pose being to induce an immunity to tuberculin. It is often 

 possible to begin with a case which reacts to o.oooi gram of tuber- 

 culin and after treatment for 6 months so change the sensitive- 

 ness that 0.5 gram may be injected without reaction. Some 

 cases do remarkably well when treated with tuberculin together 

 with the usual careful hygienic-dietetic treatment 1 given in sanito- 

 ria, but the value of tuberculin for treatment of the average case, 

 is, perhaps, not yet fully established. 2 



Bacillus Tuberculosis var. Bovinus. The bovine type of 

 tubercle bacillus is found in the lesions of tuberculous cattle 

 (perlsuchi), frequently in hogs, in a considerable percentage of 

 tuberculous lesions in children, and very rarely in the tubercu- 

 lous lungs of adult human beings. In artificial culture on solid 

 media, the cell is about i/z long, shorter than that of the human 

 type, and is easily stained. In glycerin broth the length of the 

 cell and the staining is more irregular. On all media the growth 

 is at first much less abundant than that of the human type. 

 Smith has shown that the bovine type produces alkali in glycerin 

 broth during the first two months, whereas the human type 

 tends rather to .produce acid. The virulence of the bovine 

 bacillus is greater than that of the human type for all mammals, 

 and it also infects birds. Intravenous injection of o.ooooi 

 gram of culture in thin emulsion kills rabbits with generalized 

 tuberculosis in about three weeks, while a similar dose of the 

 human variety is without such effect. Subcutaneous injection of 

 rabbits shows a similar difference. Calves are very susceptible 

 to the bovine type, not to the human. 



Tuberculosis of cattle is widely distributed and is very preva- 

 lent in the older European dairy regions. The lesions are 

 most common in the bronchial and retropharyngeal lymph glands, 

 but they may occur anywhere in the body of the animal. The 

 disease may remain localized for years in a single lymph gland or it 



1 Brown: Journ. A. M. A., 1912, Vol. LVIII, pp. 1678-81. 



2 Brown: Amer. Journ. Med. Sciences, 1912, Vol. CXLIV, pp. 469-624. 



