588 INFECTION AND IMMUNITY. 



gional or more extensive dissemination of the ba- 

 cilli throughout the lungs by respiratory forces. 

 A slower eccentric extension is seen, particularly 

 in the lungs, in which smaller and larger areas of 

 consolidation occur. By means of short lymphatic 

 metastases into contiguous territory new foci are 

 instituted, which eventually fuse with the original 

 lesion. It is suggested and generally believed that 

 bacilli may be carried longer or shorter distances 

 by wandering phagocytic cells. When tuberculosis 

 once involves a surface like that of the pleura, peri- 

 toneum, pericardium or pelvis of the kidney, the 

 whole surface frequently becomes involved in 

 thickly studded miliary tubercles. It is probable 

 that a great deal of dissemination is accomplished 

 by the movements of the fluids and the surfaces of 

 these cavities. In other instances, as in- the ure- 

 ters, Fallopian tubes and spermatic cords, exten- 

 sion seems to occur in the submucous tissue by 

 means of the lymphatics. The autopsy often dis- 

 closes that tuberculosis which appeared to be "pri- 

 mary" in such organs as bones, suprarenal glands, 

 and meninges was preceded by an old process in a 

 lymph gland from which metastases occurred to the 

 tissues in question. 



The Tubercle Certain anatomic conditions produced in tuber- 



and Tissue culosis which are associated with recovery from the 



changes. Disease, or the contrary, may be referred to. The 



tubercle, the histologic unit of the tuberculous 



process, is produced as follows, according to the 



interpretations of Baumgarten: When a bacillus 



reaches a lymph gland, for example, it multiplies 



slowly and, partly through its presence as a foreign 



body, but particularly through its toxic secretions, 



injures the surrounding connective tissue and en- 



