506 



THE RESPIRATORY SYSTEM. 



lower lobes (see Plate VII. ). It is in fact probable that in many cases 

 of acute military tuberculosis of the lung, either associated or not with 

 older local tuberculous lesions from which the distribution of bacilli may 

 have taken place, the generalization has not occurred at once but by 

 successive fresh infectious. ' 



Miliary tubercles in the lungs are in structure essentially similar to 

 those formed elsewhere in the body, except that the filling of the air 

 spaces with exudate makes the lesion somewhat more complex. 



The tubercles may be composed of small spheroidal cells or of larger 

 polyhedral cells with more or less fibrous stroma, or of small and large 

 cells and stroma. Giant cells may be present ; coagulation necrosis is 

 usual (Fig. 119, page 244). Such forms of miliary tubercles may be and 

 commonly are associated with the presence of an exudate in the adjacent 



FIG. 286. A MILIARY TUBERCLE OF THE LUNG. 



Formed of a number of air vesicles, some containing tubercle tissue, others pus and epithelium. The walls 

 of the air .vesicles are in part still preserved. 



or involved air vesicles (Fig. 284). This exudate may be largely made 

 up of exfoliated epithelial cells which have proliferated ; or with these 

 there may be serum, leucocytes, and fibrin. The blood-vessels within 

 the tubercles which replace the lung tissue are partially or wholly oblit- 

 erated (Fig. 285). 



But the miliary foci of tuberculous inflammation in the lungs may 

 consist wholly of inflammatory exudate which early becomes necrotic, 

 often with necrosis of the walls of the involved airspaces (Fig. 120, page 

 246). Such tubercles of the exudative type are apt to occur in children 

 and usually contain large numbers of tubercle bacilli. They may occur 



1 For references to the origin of miliary tuberculosis see Benda, Lubarsch and 

 Ostertag's "Ergebnisse," Jahrg. v., p. 447. 



