352 BACILLI OF NO KNOWN PATHOGENIC PROPERTIES. 



To the bacilli which produce colouring matter 

 belong : 



Bacillus prodigiosus. 

 (Micrococcus prodigious, monas prodigiosa.) 



Tliese are elliptical cells, about 1 p. in their greatest 

 diameter, distinctly rod- shaped before division, and at 

 times forming pseudo-threads. When the multiplica- 

 tion is rapid the short egg-shaped cells predominate ; 

 but their contour is seen under a high power to present 

 the form of an oblong with rounded ends, and not that of 

 a circle or ellipse. This circumstance, taken in con- 

 junction with the observation that when they grow 

 slowly, distinct rods and threads appear, renders the 

 previous designation of these organisms as micrococcus 

 no longer tenable. 



Cultiva'.io Bacillus prodigiosus grows very rapidly in nutrient 



jelly. In plates kept at 20 to 22 C., the deeply lying 

 colonies are evident after 20 hours as light grey points, 

 the superficial ones as light grey discs of about 1 mm. 

 in diameter, which are somewhat depressed and sur- 

 rounded by an area of liquefied, but perfectly clear, 

 gelatine, about 2 mm. in diameter. Under a low power 

 the deep colonies are seen to be round or oval with 

 sharp outlines, of a light reddish-brown colour, clear 

 and transparent at their margin. The superficial 

 colonies present an irregular rough outline, a granular 

 surface, and a light greyish-brown colour in their 

 middle, darker towards the periphery. The liquefac- 

 tion of the gelatine goes on so rapidly that after a few 

 hours the whole material on the plate is fluid ; this fluid, 

 as well as filter paper impregnated with it, gradually 

 assumes a bright red colour; before the gelatine is com- 

 pletely liquefied, the colonies themselves show only very 

 little of the red coloration. As the gelatine plates of 

 the bacillus prodigiosus require great attention in order 

 that they may be examined before they have become 

 completely liquid, it is on the whole better to employ 

 agar. The agar is not liquefied, and on this material 



