NON-PATHOGENIC BACILLI. (j^o 



later it becomes drier at the periphery, slightly granular, and has a striped 

 appearance. 



36G. BACILLUS MYCOIDES (Fltigge). 



Found in the soil and in water common. 



Morphology. Bacilli from 1.6 to 2.4 /* in length and about 0. 9 /* thick; 

 usually in long filaments, which when stained are seen to be made up of 

 separate elements ; as a rule, the long filaments are united in tangled bun- 

 dles. 



Biological Characters. An aerobic, liquefying, motile bacillus. Forms 

 elliptical spores from 1.3 to 1.48 n long and from 0.74 to 9 u broad. Grows 

 very rapidly best at the room temperature. Upon gelatin plates the colo- 

 nies first appear as cloudy, white spots, in which fine, white, interlaced 

 threads are soon developed; very soon a mycelial-like branching occurs, 

 giving the colony the appearance of the commencing growth of a microsco- 

 pic fungus ; as long as the bundles of filaments remain beneath the surface 

 of the gelatin they are delicate and slender, but when they reach the surface 

 they spread out, lose their sharply defined outlines, and liquefy the gelatin. 

 In gelatin stick cultures, at the end of eighteen hours, a superficial layer of 

 about four millimetres in diameter has formed and already commences to 

 sink in the gelatin; on the third day liquefaction has reached the walls of 



FIG. 233. FIG. 224. 



FIG. 223. Bacillus mesentericus vulgatus, from a culture in bouillon, x 1,000. (VignalO 

 FIG. 224. Bacillus mesentericus vulgatus, from an agar culture. X 1,400. (Vignal ) 



the test tube, and from the line of puncture a branching, filamentous growth 

 is given off; liquefaction extends downward from the surface, and after the 

 tenth day the bacterial growth is seen suspended in the liquefied gelatin. 

 Upon the surface of agar a mycelial-like, branching growth develops along 

 the line of inoculation. Upon potato, at the end of twenty-four hours, a 

 whitish-gray, shining layer, about three millimetres broad, is developed; at 

 the end of forty-eight hours this has extended over the entire surface. 



367. BACILLUS MESENTERICUS VULGATUS. 



Synonym. Potato bacillus. 



First found upon potatoes a common and widely distributed species ; 

 found in milk by Loftier, in the Freiburg water supply by Tils, in the ali- 

 mentary tract of man by Vignal. etc. 



Morphology. Thick bacilli with round ends, from 1.2 to 3.5 ju. long; often 

 united in pairs, or in chains containing several elements. 



Biological Characters. An aerobic, liquefying bacillus. Forms spheri- 

 cal spores. Grows rapidly at the room temperature also in the incubating 

 oven. Upon gelatin plates the colonies are at first almost transparent, blu- 

 ish white, later with an opaque, white centre; the superficial colonies may 

 attain a diameter of nearly one centimetre; they are somewhat sunken in 

 the liquefied gelatin ; under a low power they are seen to be granular and 

 have rough margins ; liquefaction of the gelatin is rapidly induced. In 



