670 NON-PATHOGENIC BACILLI. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing, actively motile bacillus. Spore formation not observed. Grows at the 

 room temperature in the usual culture media. Upon gelatin plates the dee}) 

 colonies appear as small, white spheres ; the superficial colonies are seen as 

 round, white, not homogeneous masses at the bottom of a funnel of lique- 

 fied gelatin; under a low power they have a granular-thready structure 

 and yellowish-gray color, and the margins are surrounded by thread-like 

 processes of various lengths. In gelatin stick cultures growth is visible 

 along the line of puncture at the end of twenty-four hours; on the second 

 or third day an air bubble is seen at the upper portion and a whitish growth 

 below; the funnel-shaped cavity gradually extends in dimensions without a 

 trace of liquid being seen, and the growth is distributed upon the walls and 

 at the bottom of this cavity ; often liquefaction occurs. Upon the surface of 

 agar a thin, uniform, gray layer is developed, which covers the entire sur- 

 face at the end of two or three days. No growth upon potato. 



359. BACILLUS GRACILIS (Zimmermann). 



Found in the Chemnitz water supply. 



Morphology. Long bacilli with round ends, usually more or less curved, 

 from 2.4 to 3.6 fj, long and about 0.77 ju broad; grow out into long filaments, 

 which are bent at an angle or present several wave-like curves. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing bacillus. Forms oval spores 1.83 // long and 1.3 fi broad. Exhibits ro- 

 tatory and oscillatory movements only. Grows slowly at the room tempe- 

 rature not in the incubating oven. Upon gelatin plates the deep colonies 

 appear as small, grayish-white spheres, which at first are well defined, but 

 later have very indistinct outlines; under a low power they are first seen as 

 sharply defined, pale-yellow discs, which are gradually surrounded by nu- 

 merous thread-like outgrowths, which after a time form a thick network. 

 Upon the surface there is no development or small, yellowish-gray, drop-like 

 colonies are seen ; at the end of five days these attain a diameter of four to 

 six millimetres and are circular in outline ; the centre is round, nebulous, 

 and bluish-gray, and outside of this one or two concentric, nebulous rings 

 are seen. In gelatin stick cultures there is a scanty growth upon the sur- 

 face, often appearing as an opalescent film, or the superficial layer of the 

 gelatin is penetrated by radiating lines given off from centres of growth 

 which do not extend above the surface. Along the line of puncture a row 

 of whitish discs is developed which are largest above ; at the end of three 

 to five weeks the upper portion of the gelatin is liquefied to some extent. 

 Upon the surface of agar a thin, irregular layer of a bluish- white color is 

 developed ; an abundant growth occurs along the line of puncture in agar 

 stick cultures. Upon potato the development is very scanty. 



*360. BACILLUS GUTTATUS (Zimmermann). 



Found in the Chemnitz water supply. 



Morphology. Bacilli with round ends, from 1 to 1.13 n long and 0.93 n 

 broad ; at first solitary or in pairs, later united in chains containing several 

 elements. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing, actively mottle bacillus. Appears to form spherical spores (?). Grows 

 best at the room temperature. Upon gelatin plates the deep colonies are 

 small, grayish- white spheres; under a low power these are seen to be finely 

 granular and have a gray or bluish-brown color. The superficial colonies 

 appear as bluish-gray drops ; under the microscope a brownish shimmer is 

 observed at the centre, while the sharply defined margins are colorless and 

 are distinguished from the surrounding gelatin only by being less transpa- 

 rent; later the outline sometimes becomes irregular. In gelatin stick cul- 

 tures an irregular, bluish-white, shining layer is developed, the surface of 



