290 TUBERCULOSIS 



In considering the relationships of the specific immune 

 reactions against the tubercle bacillus, it is to be noted that 

 while the existence of such reactions has been established, the 

 development of these to an extent likely to benefit an infected 

 animal is limited, and the production of such a lasting immunity 

 as would enable it to resist an infection or to throw off an 

 infection already established is extremely difficult or impossible. 

 There are probably factors in the pathology of the tubercular 

 process which militate against such an occurrence. This pro- 

 cess seems to differ from what occurs in more acute infections, in 

 that a local lesion may be in existence for a very considerable 

 period without other parts of the body being much or at all 

 concerned. This is especially marked in certain tubercular 

 manifestations, the outstanding example of which is lupus, in 

 which for years, while the bacilli are present and active in the 

 skin, even the adjacent lymphatic glands may show no signs of 

 disease. What underlies this apparent independence of the 

 body generally in relation to a serious condition affecting one 

 locality is unknown. Other examples of a similar process are 

 found in leprosy and also in certain chronic suppurations of the 

 skin. f 



Therapeutic Applications of the Tuberculins. We have 

 already stated that the use of the old tuberculin to mechanically 

 remove local foci of tuberculosis through the use of large doses 

 of the reagent was soon found to be impracticable, but both this 

 preparation and its modifications have been largely used in 

 what is now denominated "vaccine-therapy." It has been 

 already pointed out that the tubercular process is peculiar in 

 that the disease may exist locally without much affecting the 

 general health of the infected individual. The principle of 

 vaccine-therapy may roughly be said to be to bring into play the 

 potential but latent defensive mechanisms of the body with the 

 object of so reinforcing the cells locally attacked as to enable 

 them to destroy the invading bacteria. This is effected by 

 introducing into the body small doses of the infecting agent, and 

 is in reality an immunisation carried through after infection has 

 already taken place. For this purpose all the tuberculin pre- 

 parations, but especially tuberculin-R and the "new tuberculin," 

 have been used. In the case of both the latter, doses commen- 

 cing with from T J^ to 3^ mgrm., gradually increased, were 

 given every second day, and the rule originally laid down for 

 the regulation of the dosage was that no amount should be 

 given which raised the temperature more than '5 F. Opinion 

 varied as to the efficacy of such treatment. There was little 



