282 TUBERCULOSIS 



tubercle bacillus is one which not only has comparatively slow 

 growth, but retains its form and staining power for a much 

 longer period than most organisms. As a rule the bacilli are 

 extra-cellular in position. Occasionally they occur within the 

 giant-cells, in which they may be arranged in a somewhat radiate 

 manner at the periphery, occasionally also in epithelioid cells 

 and in leucocytes. 



FIG. 82. Tubercle bacilli in giant-cells, showing the radiate 

 arrangement at the periphery of the cells. Section of tubercular 

 udder of cow. 



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



The above statements, however, apply only to tuberculosis 

 in the human subject, and even in this case there are exceptions. 

 In the ox, on the other hand, the presence of tubercle bacilli 

 within giant-cells is a very common occurrence ; and it is 

 also common to find them in considerable numbers scattered 

 irregularly throughout the cellular connective tissue of the lesions, 

 even when there is little or no caseation present (Fig. 82). 



In tuberculosis in the horse and in avian tuberculosis the 

 numbers of bacilli may be enormous, even in lesions which are 

 not specially acute ; and considerable variation both in their 



