192 



TUBERCULOSIS 



encysted, caseous or calcareous and dead. In addition to the 

 primary focus, there may be a succession of tubercles of vari- 

 ous ages distributed in one or more organs. 



2. The lesions may be restricted to one organ, as the 

 liver, in which the primary focus has spread by continuity due 

 to its infiltrating nature until the destruction of the tissues ot 

 the organ has become so extensive that death results. Such 



cases do not seem to be common. 



3. The primary lesion may be 

 well marked and accompanied by 

 miliary tubercles sprinkled ex- 

 tensively throughout the organs 

 and tissues of the entire body. 



4. The lesions throughout 

 the body may resemble each other 

 very closely, so that difficulty 



, may be experienced in determin- 

 I ing the primary focus. 



In the lungs, two distinct 

 forms of lesions are observed, (i) 

 The air cells may be infiltrated 

 with the tuberculous mass spread- 

 ing directly from the primary 

 focus. This may be purulent, 

 caseous or calcareous. The color 

 may be whitish, gray or of a yel- 

 lowish tinge. (2) The lesions 

 may consist of miliary tubercles. 

 In later stages these nodules, 

 more or less translucent, may be- 

 come yellowish, caseated and 

 calcareous in their centers. Large 

 tubercular nodules are frequently 

 formed by the massing of several 

 of these minute tubercles. 

 When the lungs are primarily attacked the caudal (prin- 

 cipal) lobes are most frequently involved. Smith considers 



Fig. 37. Tuberculous focus in 

 lung showing areas of, (a) casea- 

 tion, (b) calcification, and (c) 

 liquefaction. 



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