290 BACTERIOLOGY. 



rise of temperature, a noticeable improvement in the 

 tuberculous process results. The amount of tuberculin 

 injected is continually increased, so as to continue the 

 moderate reactions. After several months all reactions 

 cease, the patients having become temporarily immune 

 to the toxin, but not to the growth of the bacillus. 

 Further injections are now useless until this immunity 

 has passed. During the treatment the bacilli themselves 

 have not been directly affected, and when the treatment 

 is interrupted the tuberculous process is apt to progress. 

 Many cases, however, of pure tuberculosis become cured 

 or greatly benefited by several periods of treatment. 



The substances produced in the body by the old tuber- 

 culin neutralized the tubercular toxins, according to 

 Koch, but were not bactericidal. After a series of ex- 

 periments, he considered the difficulty to be due to the 

 nature of the envelope of the tubercle bacillus, which 

 made it difficult to obtain the substance of the bacilli 

 in soluble form without so altering it by heat or chem- 

 icals that it was useless to produce immunizing sub- 

 stances. He conceived that immunity was not produced 

 in man for somewhat similar reasons possibly, the 

 bacilli never giving out sufficient toxin to cause cura- 

 tive substances to be produced. He therefore decided 

 to grind up the dried bacilli and soak them in water, 

 and thus obtain, if possible, without the addition of 

 heat, a soluble extract of the body-substance of the 

 bacilli, which he hoped would be immunizing. He 

 also tried to eliminate as much as possible of the toxic 

 products which produce fever. Biichner by a different 

 method, through crushing under a great pressure 

 tubercle bacilli mixed with sand, and thus squeezing 

 out their protoplasm, obtained a very similar substance. 



