igi2\ FATE OF TUBERCLE BACILLI OUTSIDE THE ANIMAL BODY 285 



have produced tuberculosis in test animals (guinea pigs and rab- 

 bits) by injecting dead cultures. These results have been confirmed 

 in the laboratory here. (See experiments page 312). 



The injection of dead cultures killed by heat or 

 DEADCULTU ( RES b y chemical disinfectants will produce necrosis, 



abscesses, caseation, emaciation, and death. So 

 closely do these lesions resemble those produced by the living germs 

 that it is difficult to know whether we are dealing with dead or with 

 living cultures. Rosenau 123 suggests that much of the work done 

 upon the duration of life of tubercle bacilli has little value for 

 lack of a clear criterion of death. Lesions from dead cultures, as 

 from live ones, may be characterized by giant cells. Tuberculin 

 cannot be depended upon to distinguish between the lesions pro- 

 duced by dead tubercle bacilli and those produced by live germs. 

 The reactions caused by the injection of 2 cc. of tuberculin under 

 the skin of guinea pigs with lesions produced by dead cultures are 

 similar to those caused by a like injection into guinea pigs with 

 lesions produced, from living cultures, even to the death of the 

 guinea pig. 



Most investigators have not taken into account the fact that 

 dead tubercle bacilli produce lesions, and in reporting their results 

 have taken for granted, when at autopsy even local lesions have 

 been found, that the tubercle bacilli have been alive and virulent. 

 The only safe method of distinguishing is by inoculating a second- 

 ary healthy guinea pig with a small amount of the tuberculous 

 material from the lesions of the original test animal. If the bac- 

 teria are alive, there develops a generalized tuberculosis, usually 

 severe; if dead, either no lesions at all or only a slight localized 

 effect will occur. Cultivations from this tuberculous material from 

 both the original and the secondary test animal will give further 

 evidence. If the organisms are (lead, no growth occurs; if alive, 

 growth is usually evident. This method, tho time consuming, is 

 Accessary to obtain the most trustworthy information. 



That the tubercle bacillus does not possess the re- 

 REL IL ON OF sistance to external agents as do the spore-bearing 



TUBERCLE BA- . . 1 fr\* / 7-. 



PILLI TO OTHER organisms is unquestioned. The spores of Bact. 

 ORGANISMS authracis have been known to hold their virulence 

 from ten to twelve years (Aiello and Drago 2 ). 

 We have found that the spores of B. snbtilis dried on an agar slant 

 and remaining in this state for eight years, gave growth when 

 seeded into broth. It might be expected, however, that tubercle 

 bacilli, from their waxy-fatty content and from their analogy to 

 spores in respect to staining qualities, would be more resistant to 



