MORBID ANATOMY 



141 



to its infiltrating nature until the destruction of the tissues of 

 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 accom- 

 panied by miliary tubercles sprinkled extensively 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 

 determining the primary focus. 



In the lungs, two distinct 

 forms of lesions are observed. 

 (i) The air cells maybe infil- 

 trated with the tuberculous mass 

 spreading directly from the pri- 

 mary focus. This may be puru- 

 lent, caseous or calcareous. The 

 color may be whitish, gray or of 

 a yellowish tinge. (2) The le- 

 sions may consist of miliary 

 tubercles. In later stages these 

 nodules, more or less translucent, 

 may become yellowish, caseated 

 and calcareous in their centers. 

 Large tubercular nodules are 

 frequently formed by the massing 

 of several of these minute tuber- 

 cles. 



When the lungs are pri- 

 marily attacked the caudal 

 (principal) lobes are most fre- 

 quently involved. Smith con- 

 siders the seeming predilection 

 for the larger lobes to be due to 

 mechanical conditions. The 



writer has found, however, that puration. (a) caseous 



cous centers. 



Fig. 28. Tuberculous focus 

 'ith center, {c) undergoing sup- 



(b) calcar- 



in certain herds that have been 



killed after the tuberculin test, the primary and only lung 



lesions were in the ventral and cephalic lobes. It is important 



