CONFUSION IN BACTERIUM TUBERCULOSIS. 355 



VACCINATION AGAINST TUBERCULOSIS. Recent ex- 

 periments by Pearson and Gilliland, v. Behring, and 

 others have shown that it is possible to immunize ani- 

 mals with lowly virulent tubercle bacteria of human ori- 

 gin, and after one or two injections with such organisms 

 the animals showed a marked degree of tolerance to the 

 more highly virulent bovine strains. The results of 

 experiments in this direction have been so encouraging 

 that it is probable this method may be systematically 

 utilized for the active immunization of cattle against 

 tuberculosis. 



We have reviewed the three common pathogenic 

 organisms that may be encountered in the sputum of 

 tuberculous individuals. Occasionally other species may 

 be present. The pyogenic forms are not rarely found, 

 and for some time after an attack of diphtheria the 

 bacillus of Loffler is demonstrable in the pharynx, so 

 that it, too, may be present under exceptional circum- 

 stances. 



ORGANISMS WITH WHICH BACTERIUM TUBERCULOSIS 

 MAY BE CONFUSED. 



It is important to note that in the study of tubercu- 

 losis one may fall into error unless it be borne in mind 

 that there is a group of bacilli whose members are in 

 many respects so like the genuine bacillus tuberculosis 

 as easily to be mistaken for it. While its peculiar 

 micro-chemical reaction is usually sufficient for identifi- 

 cation, particularly in connection with human patho- 

 logical lesions, it is well to remember that the confusing 

 organisms are not only characterized by the same stain- 

 ing peculiarities as bacillus tuberculosis, but may readily 



