352 BA CTERIOL OGY. 



stitutional manifestations commonly seen in cases of 

 advanced pulmonary tuberculosis are attributed. 



ENCAPSULATION OF TUBERCULAR Foci. It not 

 uncommonly occurs that round about a necrotic tuber- 

 culous focus there is formed a fibrous capsule which may 

 completely shut off the diseased from the healthy tissue 

 surrounding it ; or a tuberculous focus may, through the 

 resistance of the tissue in which it is located, be more 

 or less completely isolated. In this condition the dis- 

 eased foci may lie dormant for a long time and give no 

 evidence of their existence, until they are caused to 

 break through their envelopes by some disturbing 

 cause. With the passage of the bacilli or their spores 

 from such a focus into the vascular or lymphatic cir- 

 culation the disease may become general. 



It is to some such accident as this that the sudden 

 appearance of general tubercular infection in subjects 

 supposed to have recovered from the primary local 

 manifestations may often be attributed. The breaking- 

 down of old caseous lymphatic glands is a common 

 example of this recurrence of tuberculosis. 



PRIMARY INFECTION. Primary infection occurs 

 through either the vascular or lymphatic circulation. 

 Through these channels the bacilli gain access to the 

 tissues and become lodged in the finer capillary ramifi- 

 cations or in the more minute lymph-spaces. Here 

 they find conditions favorable to their development, 

 and in the course of their life-processes produce sub- 

 stances of a chemical nature which serve to bring 

 about characteristic changes in the immediate neighbor- 

 hood. In the beginning the fixed cells, particularly the 

 endothelial cells of the capillaries and lymph-spaces, 

 are stimulated to proliferation. With the onset of this 



