BACILLUS OF PLAGUE 



489 



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. 145), though considerable 

 variations in size occur. They have rounded ends, and in 





BJgVA- f, * 7 ' 



$1 ;Mii , 



4^%r' 



./ : V C^* > x * * ^^ v 



\ fi: -7 % -fK 



% i. /; %> *ji . * I* 



FIG. 145. Film preparation from a plague bubo, showing enormous 

 numbers of bacilli, most of which, show well-marked bipolar staining. 

 Stained with weak gentian-violet, x 1000. 



stained preparations a portion in'* the middle of the bacillus is 

 often left uncoloured, giving the so-called " polar staining." In 

 films from the tissues they are found scattered amongst the cells, 

 for the most part lying singly, though pairs are also seen. On 

 the other hand, in cultures in fluids, e.g., bouillon, they grow 

 chiefly in chains, sometimes of considerable length, the form 

 known as a streptobacillus resulting (Fig. 147). In young agar 

 cultures the bacilli show greater variation in size, and polar 

 staining is less marked than in the tissues : sometimes forms 



