G73 NON-PATHOGENIC BACILLI. 



end of three days these colonies are nearly spherical, and under the microscope 

 resemble 1 ittle balls of wool, from the margins of which fine filaments are given 

 otf ; finally they break through the gelatin and appear upon the surface as 

 one or more small, transparent droplets. At the end of four days the gelatin 

 is liquefied in saucer shape; in the middle is seen a yellowish- white or cream- 

 colored mass ; around this a ring of a still deeper color, and from this deli- 

 cate offshoots radiate toward the periphery of the saucer-shaped cavity. In 

 gelatin stick cultures a thin, round layer appears upon the surface, which 

 is often delicately wrinkled in a radial direction ; below development occurs 

 along the line of puncture in the form of a slender funnel, and 011 the third 

 day liquefaction commences ; a yellowish deposit collects at the bottom of 

 the liquefied gelatin, which is clouded throughout and contains numerous 

 flocculi of various dimensions. Upon the surface of agar a smooth, glis- 

 tening layer is developed, which is yellowish-brown by transmitted light 

 and pale bluish-green by reflected light. Upon potato an ochrous-yellow 

 layer is formed, which may have a reddish-brown tint. 



364. BACILLUS VERMICULOSUS (Zimmermann). 



Found in water. 



Morphology. Bacilli with round ends, 1.5 ju long and about 85 /j. 

 broad ; united in pairs or chains of three, or in long, worm-like filament 

 in which segmentation is very indistinct; the bacilli are surrounded by a 

 slimy envelope. 



Biological Characters. An aerobic, liquefying bacillus. The smaller 

 rods exhibit a rotatory or oscillating motion. Spore formation not observed. 

 Grows slowly at the room temperature better at 25 to 30 C. Upon gela- 

 tin plates the deep colonies appear as small, white spheres ; under a low 

 power they are seen to be nearly round, well defined, gray, and granular. 

 The superficial colonies are flat, gray, drop-like discs; under a low power 

 they are seen to be irregular in outline, with a wavy or bulging contour; 

 the interior is marked with paler lines, which cross each other in various di- 

 rections, dividing the colony into mesh-like fields; later this appearance is 

 only seen at the margin. In gelatin stick cultures a pale-gray, viscid layer 

 with finely notched margins is developed upon the surface ; after the fourth 

 day, when this has attained a diameter of about seven millimetres, liquefac- 

 tion commences and the superficial growth becomes depressed ; liquefaction 

 extends slowly toward the walls of the tube, and very slowly in a down- 

 ward direction, until about one-third of the gelatin is liquefied ; at the bot- 

 tom of this clouded liquid an abundant reddish-gray sediment is formed. 

 Upon the surface of agar a flat, smooth, glistening layer is developed ; later 

 the surface of this is opalescent. Upon potato an abundant yellowish-gray, 

 shining layer is formed. 



365. BACILLUS AEROPHILUS (Liborius). 



Found as an accidental contamination, probably from the air. 



Morphology. Slender rods of various lengths, about two-thirds as thick 

 as Bacillus subtilis; frequently united in jointed filaments. 



Biological Characters. A strictly aerobic, liquefying, non-motile ba- 

 cillus. Forms oval spores. Grows in the usual culture media at the room 

 temperature. Upon gelatin plates small, punctiform colonies are developed 

 at the end of forty hours; under alow power these are seen to be oval or 

 pear-shaped, well defined, and of a yellowish-gray color; liquefaction quick- 

 ly occurs and the colonies do not increase materially in size. In gelatin stick 

 cultures a broad, sac-like channel of liquefaction is formed, the upper part 

 of the liquefied gelatin is opaque and yellowish-gray, while the lower portion 

 is clearer simply contains suspended flocculi. Upon potato a yellowish 

 layer is formed; this has a dull, smooth surface and a paraffin-like lustre; 



