MODES OF INFECTION. 297 



selves, or they may pass on to neighboring glands, and 

 eventually be disseminated throughout the whole lymph- 

 atic system, ultimately reaching the vascular system. 



After having gained access to the bloodvessels, the 

 results are the same as those following upon intravas- 

 cular injection of the bacilh', namely, general tubercu- 

 losis quickly follows, with the most conspicuous pro- 

 duction of miliary tubercles in the lungs and kidneys, 

 less numerous in the spleen, liver, and bone marrow. 



When inhaled into the lungs, if conditions are favor- 

 able, multiplication of the bacilli quickly follows. With 

 their growth they are mechanically pressed into the 

 tissues of the lungs. As multiplication continues some 

 are transported from the primary seat of infection to 

 healthy portions of the lung tissue, there to give rise 

 to a further production of the tubercular process. 



In the same way infection through the alimentary 

 tract is in the main due to mechanical pressure of the 

 bacilli upon the walls of the intestines. Investigation 

 has shown that lesions of the intestinal coats are not 

 necessary for the entrance of tubercle bacilli from the 

 intestines into the body. They may be transported 

 from the intestinal tract into the lymphatics in the 

 same way that the fat-droplets of the chyle find 

 entrance into the lymphatic circulation. 



The evidence produced by Cornet,* together with 

 general statistical evidence, points to the lungs as the 

 most common portal of natural infection for the human 

 being. Unlike most pathogenic organisms, the tubercle 

 bacillus is believed to have the property of forming 

 spores within the tissues. These s[X>res, which are pre- 



1 Cornet : Zeit. fur Hygiene, 1889, Bd. v. S. 191. 



