NON-PATHOGENIC BACILLI. 631 



observed. Grows best at the room temperature. Upon gelatin plates small, 

 yellowish-white colonies of irregular form are developed beneath the surface, 

 which under a low power are seen to present hemispherical projections ; 

 when they break through the surface they have a mulberry -like appearance 

 and yellowish-white color. In gelatin stick cultures a wrinkled, yellowish- 

 white layer with irregular contour is developed; at the end of one or two 

 weeks it is depressed and the gelatin gradually undergoes liquefaction : an 

 abundant development of small, granular, yellowish- white colonies occurs 

 along the line of puncture. Upon potato a thin layer is formed, which 

 soon becomes dry and friable and has a grayish-yellow color. 



267. BACILLUS JANTHINUS (Zopf). 



Synonym. Yiolet bacillus. 



Found in water and in sewage (at Lawrence, Mass.). 



Morphology. Very small, slender bacilli, often associated in short fila- 

 ments; about 2 n long and 0.5 to 0.6 ft broad. 



Biological Characters. An aerobic, liquefying, motile, chromogenic 

 bacillus. Forms a bluish-violet pigment. Spore formation not observed. 

 Grows best at the room temperature. Upon gelatinplates the deep colonies 

 are spherical or oval, with an even contour ; upon coming to the surface 

 they spread out as a broad, irregular expansion with deeply notched edges ; 

 these superficial colonies are at first thin, but later increase in thickness ; a 

 deep-violet color soon appears, sometimes near the centre of the colony, 

 sometimes around its edges; the gelatin is very slowly liquefied. In gelatin 

 stick cultures a scanty growth, without color, is developed along the line of 

 puncture, and a thin, violet-colored layer upon the surface. The gelatin is 

 slowly liquefied, and an abundant violet-colored precipitate is seen at the 

 bottom of the liquefied gelatin in old cultures. Upon the surface of agar a 

 rather tough and coherent layer is developed, which has a dark-violet color. 

 Upon potato the development is rapid and covers the entire surface ; the 

 growth frequently has a beaded appearance, and the membranous growth is 

 with difficulty detached from the surface; it has a black-violet color. In 

 milk an abundant development occurs without producing coagulation, and 

 causing it to acquire a violet color. Reduces nitrate to nitrite very rapidly 

 and completely. (Above characters given by Jordan.) 



268. BACILLUS VIOLACEUS LAURENTIUS (Jordan). 



" Found in large numbers in the effluent of Tank 1 " at Lawrence, Mass. 



Morphology. Bacilli with round ends, from 3 to 3. 6 /* long and 0.7 ft 

 broad; often in pairs, and sometimes in chains of four or five elements. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing, actively motile bacillus. Produces a dark- violet pigment. Spore for- 

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

 plates the deep colonies, at the end of two days, are small, spherical, and 

 coarsely granular ; they usually have a radiating margin, and a dark centre ; 

 upon coming to the surface a thin, irregular expansion occurs and the gela- 

 tin is quickly liquefied in the vicinity of the colony ; at the centre a violet- 

 colored spot is seen, and around this a zone of slightly clouded liquid gelatin ; 

 liquefaction progresses rapidly, but the central violet mass does not mate- 

 rially increase in size. In gelatin stick cultures liquefaction occurs rapidly 

 along the line of inoculation; the liquefied gelatin is clouded and of a violet 

 color, and an abundant dark- violet precipitate accumulates at the bottom of 

 the tube. Upon agar an abundant development occurs, which at first has a 

 dark-violet color and later becomes jet-black. Upon potato an abundant 

 growth of a dark- violet color spreads over the entire surface; this soon be- 

 comes jet-black, except near the edge. In milk the bacillus develops rapidly 

 and abundantly, causing rapid coagulation of the casein and an acid reac- 

 tion; the milk acquires a deep blue- violet color. In ordinary bouillon the 



