i83 PA THOGENIC BACTERIA . 



tuberculous woman, were fatal to guinea-pigs into which 

 they were inoculated. 



The most frequent channel of infection is the respira- 

 tory tract, into which the finely-pulverized dust of rooms 

 and streets enters. Probably all of us at some time in 

 our lives inhale living virulent tubercle bacilli, yet not 

 all of us suffer from tuberculosis. Personal predisposi- 

 tion seems of great importance, for it has been shown 

 that without the formation of tubercles virulent bacilli 

 may be present for considerable lengths of time in the 

 bronchial lymphatic glands the dumping-ground of the 

 pulmonary phagocytes. 



In order that infection shall occur it does not seem 

 necessary that the least abrasion or laceration shall exist 

 in the mucous lining of the respiratory tract. The 

 tubercle bacillus is a foreign body of irritating prop- 

 erties, and, lodging upon a cell, is soon engulfed in its 

 protoplasm, or, arrested by a leucocyte, is dragged off to 

 some other region in whose narrow passages a most hos- 

 tile strife doubtless takes place. 



Infection also commonly takes place through the g as- 

 tro-intestinal tract by infected food. At present an over- 

 whelming weight of evidence points to the presence of 

 bacilli in the milk of cattle affected with tuberculosis. It 

 does not seem necessary that tuberculous ulcers shall be 

 present in the udders ; indeed, the bacilli have been 

 demonstrated in considerable numbers in milk from 

 udders without tubercular lesions discoverable to the 

 naked eye. 



The meat from tuberculous animals is less dangerous 

 than the milk, because the meat is nearly always cooked 

 before being eaten, while the milk is generally taken 

 uncooked. The bacilli enter the intestinal lymphatics, 

 sometimes produce lesions immediately beneath the mu- 

 cous membrane, and lead later on to the formation of 

 ulcers ; but generally they first involve the mesenteric 

 lymphatic glands. The thoracic, duct is sometimes af- 

 fected, and from such a lesion it is easy to understand the 



