208 BACTERIOLOGY. 



In the human subject the most common portals of 

 infection are doubtless the air- passages, the alimentary 

 tract, and cutaneous wounds. When introduced sub- 

 cutaneously the resulting process finds its most pro- 

 nounced expression in the lymphatic system. The 

 growing bacilli make their way into the fine lymphatic 

 spaces of the loose cellular tissue, are taken up in the 

 lymph stream and deposited in the neighboring lymph- 

 atic glands. Here they may remain, and give rise to no 

 alteration further than that seen in the glands themselves, 

 or they may pass on to neighboring glands and eventually 

 be disseminated throughout the whole lymphatic system, 

 ultimately reaching the vascular system. 



When having gained access to the bloodvessels, the 

 results are the same as those following upon intra- 

 vascular injection of the bacilli : general tuberculosis 

 quickly follows, with the most conspicuous production 

 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 tis- 

 sues 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 the mechanical pressure. of 

 the bacilli upon the walls of the intestines. Investiga- 

 tion has shown that lesions of the intestinal coats are 

 not necessary for the entrance of the tubercle bacilli 

 from the intestines into the body. They may be trans- 

 ported from the intestinal tract into the lymphatics in 



