BACILLI IN WATER. 403 



organism that closely resembles the bacillus pyocyaneus. It 

 liquefies gelatin rapidly, with the formation of a greenish-yellow 

 pigment, which is vividly fluorescent. Typical cultures form 

 upon glycerin-agar, which acquires* from an olive-green to a dark 

 olive-brown color. 



11. Bacillus Rubidus. This is a medium-sized rod, actively 

 motile, and arranged in threads of considerable length. It 

 generates a brownish-red pigment, both in gelatin and in agar, 

 and also in potato-cultures. Other than pigment-formation it 

 presents scarcely anything else characteristic. 



12. Bacillus Violaceus. This is a small, slender, actively 

 motile rod, that upon agar forms central spores. In its growth 

 upon gelatin-plates a bluish-violet bacterial mass appears in the 

 liquefied culture-medium. Upon agar-agar and potatoes the 

 formation of pigment is intense, and the color is dark violet, 

 almost black. 



ij. Bacillus Viscosus. This organism closely resembles the 

 bacillus fluorescens liquefaciens, from which, however, it is 

 differentiated by the formation of a chocolate-colored coating. 



14. Bacillus lanthinus. This is a motile bacillus of medium 

 size. Its appearance in growth upon gelatin-plates is usually 

 compared with the appearance of a drop of ink that has fallen 

 upon them. It forms a violet pigment in all nutrient media. 



15. Bacillus Helvolus. This appears in the form of motile 

 rods of varying length, which are oftea united into short threads. 

 These generate from a yellowish to a sulphur-yellow pigment. 

 Upon plates the colonies appear as circular, bright-yellow discs 

 that lie in a funnel of liquefaction. Upon agar an abundant 

 deposit of intensely yellow hue forms. 



16. Bacillus Prodigiosus. This is a small rod (formerly 

 designated micrococcus prodigiosus or monas prodigiosa), often 

 collected in small chains, of slight motility, occurring not rarely 

 in the air, less commonly in water, rather frequently upon amy- 

 laceous nutrient media (bread, potatoes), upon meat, and in 

 milk. It grows upon all nutrient niedia, with the development 

 of a bright-red pigment ; this is most intense on potatoes, which 

 present a blood-red coating. Upon gelatin-plates rather deep, 

 small, white dots appear, and . also superficial, roundish, red 

 colonies with an irregular border. Gelatin is energetically 

 liquefied. Upon agar-agar a coating of moderately dark-red 

 color appears, while the nutrient medium itself is not discolored. 

 On cultivation at a temperature of 37 C. (98.6 F.) the pro- 

 digiosus loses its red color in the course of several generations. In 

 cultures, especially upon potato, in addition to the red pigment, 

 trimethylamin forms (odor of pickled herring). Coagulation 

 is induced in milk. Saccharine nutrient media undergo fermen- 

 tation. The prodigiosus will thrive also in the absence of oxy- 



