438 



PLAGUE. 



from the bodies of these animals found dead in the plague- 

 stricken district, the same bacillus was obtained by Kitasato 

 and also by Yersin. 



Bacillus of Plague Microscopical Characters. As 

 seen in the affected glands or buboes in this disease 

 the bacilli are small oval rods, somewhat shorter than 

 the typhoid bacillus, and about the same thickness 

 (Fig. 113). They have rounded ends, and in stained 

 preparations a portion is sometimes left unstained in the 



middle of the bacilli, 

 giving the so-called 

 " pole-staining." In 

 the tissues they are 

 found scattered 

 amongst the cells, 

 for the most part lying 

 singly, though pairs 

 are also seen ; but 

 in cultures, especially 

 in fluids, they have 

 a tendency to grow 

 into chains, the form 

 known as a strepto- 

 bacillus resulting 

 FIG. 114. Bacillus of plague in chains /pjg 114) Some 

 showing polar staining. From a young . * . , 

 culture in bouillon. times m the tlSSUCS 



Stained with thionin-blue. x 1000. they are seen to be 



surrounded by an 



unstained capsule, though this appearance is by no means 

 invariable. They do not form spores. Gordon, who has 

 shewn that they possess flagella which, however, stain with 

 difficulty, states that they are motile. They stain readily 

 with the basic aniline stains, but are decolorised by Gram's 

 method. 



Anatomical Changes and Distribution of Bacilli. The 

 disease occurs in several forms, the bubonic and the 

 pulmonary being the best recognised ; to these may be 

 added the scpticamic. ' The most striking feature in the 



