120 BACTERIAL POISONS. 



covered with a vegetable resin, then smeared with the slime 

 of swampy places. 



LiERMANN found that material taken from the arm of a 

 man who had died from tetanus, and who had been buried 

 for two and one-half years, induced tetanus in animals. 

 This would seem to show that the poison retains its viru- 

 lence for a long time. In this material there were found 

 nine kinds of bacteria, but none of these in pure culture, 

 or in mixed culture, induced the disease. This is explained 

 by the supposition that non-pathogenic bacteria may receive 

 toxicogenic properties from the media in which they grow. 



Tuberculosis. — Whatever may be the ultimate verdict 

 concerning the curative properties of Koch's tuberculin, its 

 employment has made us familiar with the action of the 

 chemical products of the bacillus tuberculosis on man. Un- 

 fortunately, Koch has given us but little information con- 

 cerning the nature of his tuberculin, and the little which he 

 has given us has been to some extent misleading. We 

 would not imply that he has intentionally been misleading. 

 Indeed, we believe that such was not his intention. He 

 speaks of the agent as an extract of a pure culture of the 

 bacillus tuberculosis with 50 per cent, glycerin. One would 

 infer from Koch's statements that tuberculin is prepared 

 by extracting the bacterial cells with 60 per cent, glycerin, 

 and that the bacterial products are not present. But, 

 as has been shown by Hubppe and Scholl, the proteids 

 of the cells of the bacillus tuberculosis cannot be extracted 

 with 50 per cent, glycerin. Moreover, the same investiga- 

 tors have prepared a fluid identical in physical properties, 

 in chemical reactions, and in its eflects on animals, with 

 Koch's fluid, by each of the three following methods : 



1. Cultures of the bacillus are filtered, sterilized by heat, 

 and concentrated. 



2. The supernatant, fluid portion of the culture is de- 

 canted from the mass of germs at the bottom of the flask, 

 and then concentrated. 



3. The culture is freed from germs by filtration through 

 a Chamberland filter, and concentrated. 



