TUBERCULOSIS. 321 



the slightest influence upon the tubercle bacillus, but acts 

 upon the tuberculous tissue. In the description of the 

 tissue-changes already given it has been shown that the 

 tubercle bacillus effects the coagulation-necrosis of the 

 cells, but does not derive its nutriment from the dead 

 tissue. As the cells die and are incorporated in the 

 necrotic mass, the bacilli find the conditions of life un- 

 favorable, and likewise die. The active bacilli, therefore, 

 are found at the margins of the tuberculous tissues, where 

 the cells are fairly active. The necrosis is due to bacillary 

 poisons. When tuberculin is injected into the organism 

 the result is to augment greatly the amount of poisonous 

 influence upon the cells surrounding the bacilli, to destroy 

 their vitality, to remove the favorable conditions of growth 

 from the organism, and to leave it for a time checkmated. 

 This action of tuberculin is accompanied by a marked 

 hyperemia of the peri-tuberculous tissue, with transuda- 

 tion of serum, softening of the tuberculous mass, and 

 absorption of poisonous material into the blood. The 

 process is always followed by a marked febrile reaction. 



Virchow, who well understood the action of the tuber- 

 culin, soon showed that as a diagnostic and therapeutic 

 agent in man its use was attended with great danger. 

 The destroyed tissue was absorbed, and with it the bacilli, 

 which were transported to new areas, in which a rapid 

 invasion occurred. Old tuberculous lesions which had 

 been encapsulated were softened, broken down, and be- 

 came sources of dangerous infection to the individual, so 

 that, a short time after its enthusiastic reception as a 

 "gift of the gods," tuberculin was placed upon its proper 

 footing as a diagnostic agent valuable in veterinary prac- 

 tice, but dangerous in human medicine, except in cases 

 of lupus and other external forms of the disease where the 

 destroyed tissue could be discharged from the surface of 

 the body. 



A recent important work upon tuberculin done by Koch 1 

 has resulted in a new preparation, TR or tuberculin-R. 



1 Deutsche med. Wochenschrift, 1897, No. 14. 

 21 



