NOX-PATHOGENIC BACILLI. 625 



Biological Characters. An aerobic, non-liquefying, actively motile, 

 fhromogenic bacillus. Forms a green pigment, which after several weeks 

 becomes yellowish-brown and then dark-green and fluorescent. Spore 

 formation not observed. Grows best at the room temperature rather slowly. 

 Upon gelatin, plates the deep colonies are small and spherical ; the superficial 

 colonies are flat, with irregular but well-defined margins and a finely gran- 

 ular surface; at the end of two to three days the colony and the surrounding 

 gelatin have an intensely green color ; later the colony becomes thicker, softer, 

 and of a still deeper green color. In gelatin stick cultures growth occurs on 

 the surface only ; the gelatin acquires a decided green color. Upon agar an 

 abundant development occurs upon the surface. Upon potato a nut-brown, 

 moist layer is formed, and the potato around it acquires a dirty-violet color. 

 In bouillon forms a layer upon the surface, which is with difficulty made to 

 sink to the bottom, and not until it is broken up by shaking ; the upper por- 

 tion of the bouillon has a green color. 



252 BACILLUS IRIS (Frick). 



Morphology. Very small, slender bacilli. 



Biological Characters. An aerobic, non-liquefying, non-motile, chromo- 

 genic bacillus. Produces a fluorescent green color, which later becomes 

 yellowish-brown, and finally dark-green and fluorescent. Spore formation 

 not observed. Grows best at the room temperature. Upon gelatin plates 

 forms prominent, whitish, round, sharply defined superficial colonies with 

 a, smooth, shining surface ; a green color is slowly developed. In gelatin 

 stick cultures a prominent mass develops about the point of puncture ; no 

 growth along the line of puncture. Upon potato a dry, pale-brown layer is 

 formed. In bouillon no layer is formed upon the surface, and the bouillon 

 is not colored 



253. BACILLUS FUSCUS (Zimmermann). 



Found in water. 



Morphology. Straight or curved bacilli with round ends, an irregular 

 contour, here and there slightly bulging ; about 0.63yu in diameter and of 

 various lengths. 



Biological Characters. An aerobic, non-liquefying, non-motile, chromo- 

 genic bacillus. Forms a dark chrome-yellow pigment. Spore formation 

 not observed. Grows slowly at the room temperatm-e in the usual culture 

 media best at 30 C. Upon gelatin plates the deep colonies are punctiform 

 -and yellowish-brown in color ; later they project from the surface in button 

 form, and often have an irregular, knobby form ; under the microscope such 

 colonies are seen to be made up of smaller, spherical masses. The deep col- 

 onies, under a low power, are spherical or irregular in form, granular, and 

 grayish-yellow or brownish -yellow in color ; the superficial colonies have a 

 brownish-yellow central portion surrounded by a highly refractive marginal 

 zone. In gelatin stick cultures a button-like mass develops at the point of 

 puncture; later the growth extends over the surface, forming a thick, 

 wrinkled layer, at first pale-yellow and then chrome-yellow in color. The 

 growth upon agar is similar to that upon gelatin. Upon potato a dark 

 chrome-yellow, friable layer is developed. 



254. BACILLUS RUBEFACIENS (Zimmermann). 



Found in the Chemnitz water supply. 



Morphology. Bacilli with round ends, from 0.75 to 1.65 /* long and about 

 0.32 n thick; united in pairs, or in chains consisting of several elements. 



Biological Characters. An aerobic, non-liquefying, actively motile, 

 chromogenic bacillus. Produces a pale-pink pigment. Grows best at the 

 room temperature. Upon gelatin plates the deep colonies are spherical or 

 lenticular in form, and white with a shade of yellowish-red ; the superficial 



