34 BACILLUS TUBERCULOSIS 



This power of resistance to the decolorising 

 action of acids has been shown by Klebs and others 

 to be due to the presence in the bacillus of a fatty 

 body, extraction of which removes the specific stain- 

 ing property. 



When stained by this method a specimen of 

 tubercular sputum examined with a magnification 

 of 500 diameters presents the appearance shown in 

 Fig. 25. Amongst the scattered nuclei of cells are 

 seen numbers of fine red-stained bacilli of very vary- 

 ing length and curvature, sometimes lying singly 

 and sometimes collected into groups. 



Examined with a higher power (Figs. 26 and 27), 

 the bacillus usually presents a highly characteristic 

 dotted or beaded appearance. Within a delicate 

 sheath the protoplasm is collected into regular 

 strongly stained masses separated by comparatively 

 clear spaces. This appearance was originally 

 ascribed to spore formation, but is now regarded as 

 a segregation of the protoplasm without relation to 

 spore formation. 



This beading of the bacillus is by no means 

 constant and may be entirely lacking as the photo- 

 graps show. Not unfrequently there is a ten- 

 dency for the bacilli to lie in pairs parallel to 

 one another, and occasionally (Figs. 27 and 28) 



