620 NON-PATHOGENIC BACILLI. 



colonies are flat, gray with a reddish tint ; under the microscope the deep 

 colonies are seen to be granular, spherical, and yellowish or brownish in 

 color. In gelatin stick cultures development occurs along the line of punc- 

 ture, and upon the surface a tolerably thick, grayish-white layer is formed, 

 which later has a yellowish tint, while the gelatin around it has a bluish- 

 white lustre. In old cultures the gelatin frequently acquires a pale wine 

 color. Upon agar a smooth, rather thick, bluish-gray layer is formed. 

 Upon potato an abundant, yellowish-gray layer is developed, which later 

 has a reddish-brown color, while the potato around it after forty -eight hours 

 acquires a pink color. 



255. BACILLUS STRIATUS FLAVUS (Von Besser). 



Found in nasal mucus rare. 



Morphology. Small, thick rods, often curved, of about the dimensions 

 of the diphtheria bacillus. In preparations stained with methylene blue, has 

 a striated appearance. In old preparations various involution forms are 

 seen. 



Biological Characters. An aerobic, non-liquefying, chromogenic bacil- 

 lus. Forms a sulphur- yellow pigment. Grows at the room temperature in 

 the usual culture media. Spore formation not observed. Upon gelatin 

 plates forms thick, dry, granular colonies of a yellowish color. Upon agar 

 plates projecting milk-white colonies of about 0.5 centimetre in diameter 

 are developed ; later these acquire a sulphur-yellow color. Upon the sur- 

 face of agar a white, thick layer develops along the impfstrich ; after some 

 days this acquires a sulphur-yellow color. Upon potato a narrow, yellow 

 stripe is developed along the impfstrich. 



256. BACILLUS SUBPLAVUS (Zimmermann). 



Found in the Chemnitz water supply. 



Morphology. Bacilli with round ends, from 1.5 to 3;* long and about 

 0.77 n broad ; united in chains of several elements. 



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

 genic bacillus. Forms a pale-yellow pigment. Grows best at the room tem- 

 perature. Spore formation not observed. Upon gelatin plates the deep colo- 

 nies are small, yellowish-white, and spherical; these break through the 

 surface and form hemispherical, yellowish-white, shining masses, which 

 later extend over the surface and have an irregular outline; under a low 

 power the surface is seen to have a pearly lustre ; they gradually acquire a 

 dirty-yellow color. In gelatin stick cultures a thin, yellowish-gray layer 

 with finely dentate margins forms about the point of puncture. Upon the 

 surface of agar a pale-yellow layer gradually extends over the entire sur- 

 face; the color gradually becomes darker and is finally between a pale 

 chrome-yellow and yellow ochre. Upon potato a scanty, dull, clay-yellow 

 layer is formed. 



257. BACILLUS CYANOGENUS (Hueppe). 



Synonyms. Bacterium syncyanum; Bacillus lactis cyanogenus; Bacil- 

 lus of blue milk. 



Found in milk. 



Morphology. Bacilli with slightly rounded corners, from 1.4 to 4 n long 

 and from 0.3 to 0.5 n broad. 



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

 chromogenic bacillus. Produces a grayish-blue pigment. Forms spores, 

 which are located at the extremities of the rods, giving them a club shape. 

 Grows rapidly at the room temperature or in the indicating oven. Upon 

 gelatin plates, at the end of two days, small, punctiform, grayish -white 

 colonies are developed ; the superficial colonies appear as slimy drops which 



