ACTION ON THE TISSUES 



271 



*ire present. In subacute lesions, with well-formed tubercle 

 follicles and little caseation, the bacilli are generally scanty. 

 They are most numerous in acute lesions, especially where 

 caseation is rapidly spreading, for example, in such conditions as 

 case. HI* catarrlial pneumonia (Fig. 80), acute tuberculosis of the 

 spleen in children, which is often attended with a good deal of 

 rapid casemis change, etc. ; in such conditions they often form 



*" 



Fi<;. 81. 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 Rismarrk-brown. x 1000. 



large masses which are easily seen under a low power of the 

 microscope. In acute miliary tuberculosis a few bacilli can 

 generally be found in the centre of the follicles ; but here they 

 are often much more scanty than one would expect. The 

 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 jK)sition. Occasionally they occur within the 

 iriant -cells, in which they may lie arranged in a somewhat radiate 



