1 84 PATHOGENIC BACTERIA. 



of tubercles), and a widespread invasion of the lungs, 

 liver, kidneys, peritoneum, and other organs and tissues, 

 with tuberculous tissue in a more or less advanced con- 

 dition of necrosis. Sometimes there are no tubercles 

 discoverable at the point of inoculation. There is no 

 regularity in the distribution of the disease. Tubercle 

 bacilli are demonstrable in immense numbers in all the 

 diseased tissues. The disease as seen in the guinea-pig is 

 more extended than in other animals because of its greater 

 susceptibility, and the death of the animal is more rapid 

 than in other species for the same reason. In rabbits the 

 lesion runs a longer course with similar lesions. In 

 bovines and sheep the infection is generally first seen 

 in, and is principally confined to, the alimentary appa- 

 ratus and the associated organs, though pulmonary dis- 

 ease also occurs. In man the disease is chiefly pulmonary, 

 though gastro-intestinal and general miliary forms are also 

 common. The development of the lesions in whatever 

 tissue or animal always depends upon the distribution of 

 the bacilli by the lymph or the blood, and is first inflam- 

 matory, then degenerative, in type. 



The experiments of Koch, Prudden and Hodenphyl, 

 and others have shown that when dead tubercle bacilli 

 are injected into the subcutaneous tissues of rabbits 

 small local abscesses develop in the course of a couple 

 of weeks, showing that the tubercle bacilli are chemotac- 

 tically potent. 



While it is extremely interesting to observe that this 

 chemotactic property exists, it seems to be by some other 

 irritant that most of the lesions of tuberculosis are caused. 

 When the dead tubercle bacilli, instead of being injected 

 en masse into the areolar tissue, are so introduced info 

 the body as by intravenous injection as to disseminate 

 themselves or remain in small groups, the result is quite 

 different, and much more closely resembles that of the 

 action of the living organism. 



Baumgarten, whose researches were made upon minute 

 tubercles of the iris, has shown that the first manifesta- 



