NON-PATHOGENIC BACILLI. 665 



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

 formation not observed. Motion slow and sinuous. Grows at the room 

 temperature in the usual culture media much better at 37 C. Upon gela- 

 tin plates the deep colonies send out long, spiral filaments, which give a hazy 

 appearance to the colony ; under a low power the colony, surrounded by ra- 

 diating filaments, resembles a jelly-fish with streaming tentacles; the sur- 

 rounding gelatin is slowly liquefied. Oncoming to the surface the colony 

 spreads out as an irregular expansion, under which the gelatin is slowly 

 liquefied, and at the same time dried out so as to form shallow, cup-shaped 

 depressions.; the surface of these cavities is mottled in appearance, as if cov- 

 ered with a fine, irregular reticulation. In gelatin stick cultures, at the end 

 of two days, the growth at the surface resembles a cup with flaring edges ; 

 liquefaction occurs slowly, and the liquefied gelatin is dried by evaporation, 

 so that the cup-shaped cavity gradually increases in dimensions ; it is lined 

 with a reticulated growth similar to that seen in the colonies upon gelatin 

 plates ; at the end of three days fine filaments begin to grow out from the line 

 of puncture, but these do not reach any considerable length. This bacillus 

 exhibits a scanty development under a mica plate. Upon the surface of agar 

 ,a prominent, dull, dry layer is slowly developed. Upon potato a white, 

 dull, dry layer is developed at the end of two days, and at the end of five 

 days this has a characteristic woolly appearance. Milk acquires an acid re- 

 .action and is slowly -coagulated fifteen to twenty days at the room tempe- 

 rature. Bouillon slowly becomes turbid and a slight viscid sediment is 

 formed. Nitrates are rapidly reduced to nitrites by this bacillus. 



348. BACILLUS HYALINUS (Jordan). 



Found in large numbers in the sand of Tank 13 at Lawrence, Mass., "at 

 ;a time when the tank was nitrifying well.'' 



Morphology. Bacilli with round ends, from 3. 6 to 4 /* long and 1.5 JJ. 

 broad ; usually united in short chains. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

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

 usual culture media at the room temperature better at 37 C. Upon gelatin 

 plates the colonies are visible at the end of twenty-four hours; they are seen 

 to consist of a dark central nucleus surrounded by a broad, translucent zone, 

 which gives the colonies a hazy appearance ; under a low power the interior 

 is seen to present a coarsely fibrillar appearance, with short fibrils radiating 

 from the edge. In two days the colonies attain a diameter of about one and 

 one-half centimetres; they are round in contour, with a distinct, opaque, 

 yellowish margin, from which radiating fibrils are given off ; the interior is 

 slightly translucent. In gelatin stick cultures, at the end of two days, a 

 long and narrow, funnel-shaped growth is seen; the gelatin is rapidly lique- 

 fied and is at first -clouded, with a white deposit at the bottom of the funnel; 

 later a lustrous and tenacious white layer is seen upon the surface and a 

 slight flocculent deposit at the bottom, while the liquefied gelatin between 

 is entirely transparent. This bacillus grows well in acid gelatin. Upon the 

 surface of agar a dry., grayish, spreading growth is rapidly developed ; 

 when four or five days old small, warty projections are seen ; growth also 

 occurs along the line of puncture in agar stick cultures. Upon potato, at 

 the end of two days, the growth is just visible; at the end of four days a 

 dry, whitish-gray, spreading layer is developed; later small protuberances 

 .are seen upon the surface of this. In milk a strongly acid reaction with co- 

 agulation of the casein is produced in seven days. In bouillon a diffuse 

 cloudiness is quickly produced ; a viscid sediment is formed and a myco- 

 derma forms upon the surface. This bacillus reduces nitrates vigorously and 

 rapidly. 



349. BACILLUS CLOAC.E (Jordan). 



Isolated from sewage at Lawrence, Mass. "one of the most common 

 ibacteria in sewage." 



