436 APPLICATION OF METHODS OF BACTERIOLOGY 



In the contents and in the walls of tubercular cavities 

 in man bacteria other than bacillus tuberculosis are found. 

 It is to the influence of some of these, as we have seen, that 

 diseases other than tuberculosis may sometimes be produced 

 by the inoculation of animals with the sputum from such 

 cases; and it is also to the absorption of their toxic products 

 that some of the constitutional manifestations, particularly 

 fever, commonly seen in cases of advanced pulmonary tuber- 

 culosis are attributed. 



Encapsulation of Tubercular Foci. It not uncommonly 

 occurs that round about a necrotic tuberculous 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 diseased foci may lie dormant for a 

 long time and give no evidence of their existence, until 

 they are made to break through their envelopes by some 

 disturbing cause. With the passage of the bacilli from such 

 a focus into the vascular or lymphatic circulation the disease 

 may become general. 



It is to some such accident as this that the sudden ap- 

 pearance 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 ramifications or in the 

 more minute lymph spaces. Here they find conditions 



