238 



TUBERCULOSIS. 



but retains its form and staining power for a much longer 

 period than most organisms. This is true of the bacilli 

 both in cultures and also in the tissues. 



As regards their position in the tissues, the bacilli are 

 usually scattered irregularly or in small groups amongst the 

 cells or granular material. Most of the bacilli lie free, 



FIG. 65. 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-fuchsin and Bismarck-brown. x 1000. 



and their occurrence within the cells is relatively un- 

 common, there being in this respect a contrast to what is 

 seen in the lesions in leprosy. Occasionally we find them 

 within the giant cells, in which they may be arranged in a 

 somewhat radiate manner at the periphery, occasionally also 



