270 



TUBERCULOSIS 



especially pyogenic, organisms, secondarily present in the tuber- 

 cular lesions. This matter, however, requires further elucidation. 

 Presence and Distribution- of the Bacilli. A few facts may 

 be stated regarding the presence of bacilli, and the numbers in 

 which they are likely to be found in tubercular lesions. 

 They are usually very few in number in chronic lesions, 

 whether these are tubercle nodules with much connective tissue 



FIG. 80. Tubercle bacilli in section of human lung in acute phthisis. 

 The bacilli are seen lying singly, and also in large masses to left of 

 field. The pale background is formed by caseous material. 



Stained with carbol-fuchsiu and Bismarck-brown, x 1000. 



formation or old caseous collections. In caseous material one 

 can sometimes see a few bacilli faintly stained, along with very 

 minute unequally stained granular points, some of which may 

 possibly be spores of the bacilli. Whether they are spores or 

 not, the important fact has been established, that tubercular 

 material in which no bacilli can be found microscopically, may 

 be proved, on experimental inoculation into -animals, to be still 

 virulent. In such cases the bacilli may be present in numbers so 

 small as to escape observation, or it may be that their spores only 



