258 TUBERCULOSIS. 



one or two bacilli are found, especially if they deviate in their 

 morphological characters from the tubercle bacillus. 



Action of Dead Tubercle Bacilli. — The remarkable fact has 

 been established by independent investigators that tubercle bacilli 

 in the dead condition, when introduced into the tissues in suffi- 

 cient numbers, can produce tubercle-like nodules. Prudden and 

 Hodenpyl, by intravenous injection in rabbits of cultures ster- 

 ilised by heat, produced in the lungs small nodules in which 

 giant-cells, but no caseation, were occasionally present, and 

 which were characterised by more growth of iibrous tissue than 

 in ordinary tubercle. The subject has been very fully investi- 

 gated with confirmatory results by Straus and Gamaleia, who find 

 that, if the number of bacilli introduced into the circulation is 

 large, there result very numerous tubercle nodules with well- 

 formed giant-cells, and occasionally traces of caseation. The 

 bacilli can be well recognised in the nodules by the ordinary 

 staining method. In these experiments the bacilli were killed 

 by exposure to a temperature of 115° C. for ten minutes before 

 being injected. Similar nodules can be produced by intraperi- 

 toneal injection. Subcutaneous injection, on the other hand, 

 produces a local abscess, but in this case no secondary tubercles 

 are found in the internal organs. Further, in many of the ani- 

 mals inoculated by the various methods a condition of marasmus 

 sets in and gradually leads to a fatal result, there being great 

 emaciation before death. These experiments, which have been 

 confirmed by other observers, show^that even after the bacilli 

 are dead they preserve their staining reactions in the tissues for 

 a long time, and also that there are apparently contained in the 

 bodies of the dead bacilli certain substances which act locally, 

 producing proliferative, and to a less extent degenerative, 

 changes, and which also markedly affect the general nutrition. 

 The long period during which the tubercle bacillus, as compared 

 with other organisms, retains even when dead its morphological 

 and staining characters, is a very striking feature. S. Stockman 

 has recently found that an animal inoculated with large numbers 

 of dead tubercle bacilli afterwards gives the tuberculin reaction. 



Practical Conclusions. — From the facts above stated with 

 regard to the conditions of growth of the tubercle bacilli, their 

 powers of resistance, and the paths by which they can enter the 

 body and produce disease (as shown by experiment), the man- 



