it exhibits the property of metachromasia, wherein the granules appear in a colour other than the colour used for staining. When stained with polychrome methylene blue, the granules appear violet while the rest of the bacillus appears blue. The granules are made up of polymetaphosphates and are known by various other names such as volutin bodies, Babe-Ernst granules or polar bodies. The bacterium produces the granules in abundance when grown on nutrient rich medium such as Loeffler's serum slope.