414 



BACTERIA PATHOGENIC TO MAN 



length of the bacilli varies, but on the average is about 1.6// (1.5// to 1.7/*), 

 breadth 0.5/* to 0.7/*. Besides the usual oval form the plague bacillus 

 has many exceptional variations which are characteristic of it. In 

 smears especially from old buboes one looks for long bacilli with clubbed 



FIG. 129 



Involution forms on salt agar. (Kolle and Wassermann.) 



ends (similar to involution forms, Fig. 129), yeast-like forms, and 

 bladder shapes. Some of these stain with difficulty. When obtained 

 from cultures the bacilli present not only the forms already mentioned, 

 but also long chains. 



FIG. 130 



Bacilli in acutely inflamed gland. 



Staining. They stain readily with the ordinary aniline dyes, and 

 especially well with methylene blue, the ends being usually more deeply 

 colored than the central portion; does not stain by Gram's method. 



