ACTION OF DEAD TUBERCLE BACILLI. 227 



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 intraperitoneal 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 animals 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, degene- 

 rative 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. 



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 manner by which tuberculosis is naturally 

 transmitted can be readily understood. Though the ex- 

 periments of Sander show that tubercle bacilli can multiply 

 on vegetable media to a certain extent at warm summer 

 temperature, it is doubtful whether all the conditions 

 necessary for growth are provided to any extent in nature. 

 At any rate, the great multiplying ground of tubercle bacilli 

 is the animal body, and tubercular tissues and secretions 

 containing the bacilli are the chief, if not the only, means 

 by which the disease is spread. The tubercle bacilli leave 



