18 CLINICAL APPLIED ANATOMY. 



established foci local extension may occur radially by means of 

 lymphatics and also by direct continuity of tissue. During the 

 progress of a tuberculous lesion an incompletely thrombosed 

 artery may be opened, and localised embolic miliary tuberculosis 

 be set up in the part of the lung to which the invaded vessel is 

 distributed. 



A distinctive feature of lung tuberculosis in childhood is the 

 direct infection of lung tissue by adjacent tuberculous lymphatic 

 glands. Since glands can be traced into the lungs as far as the 

 fourth subdivision of the bronchi, they are apt to appear as 

 embedded caseous masses, and may be confused with true 

 pulmonary deposits. 



It is also possible for the lungs to be invaded through the 

 blood stream as part of a disseminated miliary tuberculosis, and 

 some authorities believe that phthisis is of embolic origin. 



The serous membranes are frequently the sites of tuberculosis. 



Invasion of the pleura is often secondary to that of the lung 

 and the bronchial glands. The intimate relation of the visceral 

 pleura to the lung, the subpleural course of many efferent 

 pulmonary lymphatics, the termination of these lymphatics in 

 the bronchial glands, and the close relation of the glands 

 themselves to the pleura, all facilitate invasion of the latter, 

 which may either occur by direct continuity or possibly by 

 lymphatic backflow. The pleura may also be invaded by the 

 medium of the blood stream, but its vessels are comparatively 

 unimportant. Yet another path for pleural invasion is from the 

 peritoneum through the lymphatics of the diaphragm. Carious 

 ribs or vertebrae may infect the pleura by contact. 



Very similar considerations apply to pericardial infection. 

 This sac is adjacent to the lungs and pleurae, also to the sternum, 

 ribs, and dorsal vertebrae ; the bronchial and other mediastinal 

 glands are in close apposition to it. From any of these sources 

 tuberculosis may spread. It is also open to infection from below 

 through the diaphragm and by the blood stream. 



The peritoneum maybe invaded by means of the blood stream, 

 but, as is the case with the pleurae, its vessels are small and 



