BACTERIUM TUBERCULOSIS 447 



reaction results, consisting of sudden but temporary ele- 

 vation of temperature, with, at the same time, the occur- 

 rence of marked hyperemia about the tuberculous focus, 

 a change histologically analogous to that seen in the pri- 

 mary stages of acute inflammation. This zone of hyperemia, 

 with the coincident exudation and infiltration of cellular 

 elements, probably aids in the isolation or casting off of 

 the tuberculous nodule, the inflammatory zone forming, 

 so to speak, a line of demarcation between the diseased and 

 healthy tissue. 



As a curative agent for tuberculosis, tuberculin has not 

 proved worthy of the confidence that was at first accorded 

 to it. Its field of usefulness is now almost limited to the 

 diagnosis of obscure cases. 



In veterinary medicine it has proved trustworthy as a 

 diagnostic aid, and is practically everywhere in use for the 

 detection of incipient tuberculosis in cattle. 



VACCINATION AGAINST TUBERCULOSIS. Experiments by 

 Pearson and Gilliland, v. Behring, Calmette, and others have 

 shown that it is possible to partly immunize animals with 

 lowly virulent tubercle bacteria of human origin. After one 

 or two injections with such organisms the animals showed for 

 a time some degree of tolerance to the more highly virulent 

 bovine strains. The results of experiments in this direction 

 have been so encouraging as to justify further research 

 in this direction, but complete immunity has not as yet 

 resulted. 



We have reviewed the three common pathogenic organ- 

 isms 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 



