TUBERCULOSIS 159 
anatomical changes. It may be entirely encysted, caseous or cal- 
careous and dead. In addition to the primary focus, there may be a 
succession of tubercles of various ages distributed in one or more 
organs. 
The lesions may be restricted to one organ, as the liver, in which 
the primary focus has spread by continuity due to its infiltrat- 
ing nature until the destruction of the tissues of the organ has be- 
come so extensive that death results. Such cases do not seem to be 
common. 
sec PT 
Fic. 33. TUBERCLE DISCHARGING INTO BRONCHUS. THIS SHOWS A SECTION THROUGH a 
BRONCHUS WHERE AT POINT (a) THE TUBERCULOUS TISSUE HAS EXTENDED INTO THE 
BRONCHUS MAKING IT POSSIBLE FOR THE TUBERCLE BACTERIA FROM THE TUBERCULOUS 
AREA TO PASS INTO THE BRONCHUS AND THROUGH IT TO THE MOUTH. FROM THE 
MOUTH THEY ARE DISSEMINATED WITH THE DROOLINGS OR THEY ARE SWALLOWED AND 
APPEAR IN THE INTESTINAL CONTENTS. (NATURAL SIZE). 
The primary lesion may be well marked and accompanied by 
miliary tubercles sprinkled extensively throughout the organs and 
tissues of the entire body. 
The lesions throughout the body may resemble each other very 
closely, so that difficulty may be experienced in determining the prim- 
ary focus. 
In the lungs, two distinct forms of lesions are observed. (1) The 
air cells may be infiltrated with the tuberculous mass spreading 
