298 J. S. LAWRENCE AND W. W. FORD 



Gelatin colonies. Surface colonies round, granular, punctiform 

 with slow liquefaction. Some of the larger colonies are spreading 

 and have a glassy surface. Deep colonies punctiform, spherical 

 with dense centers. 



Broth. Slight turbidity with no surface growth but a floccu- 

 lent precipitate. Medium is eventually turned dark yellow. 



Peptone. Slight turbidity with no surface growth and no 

 precipitate. 



Potato. Yellow, moist growth becoming a reddish brown. 

 Medium is discolored. 



Milk. No change in 48 hours. In twenty days the medium 

 shows an acid reaction with the precipitation of a white sediment. 



Blood serum. Thick, transparent spreading growth with 

 irregular edges. 



Fermentation tubes. Glucose. Turbidity in open bulb. No 

 scum. No growth in closed arm. Reaction acid. 



Saccharose. Turbidity. No scum. No growth in closed 

 arm. Reaction alkaline. 



Lactose. Turbidity. No scum. No growth in closed arm. 

 Reaction alkaUne. 



Thermal death point. Spores withstood one hour's sterihzing 

 in the Arnold sterilizer, survived autoclaving at 15 pounds 

 pressure but were killed by 16 pounds pressure. 



Bacillus aterrimus Lehmann & Neumann. 



This organism was originally described by Biel (1896) and 

 named by Lunt (1896) Bacillus mesentericus-niger. It is not 

 uncommon in milk, soil, and the intestinal contents of man. 



Morphology. Bacilh similar to Bacillus vulgatus in morphol- 

 ogy. On plain agar they are homogeneous with blunt ends and 

 measure about 0.5 by 2 to 3 microns in dimensions. On glucose 

 agar they are thicker and longer measuring 0.75 by 2 to 4 microns 

 but at the same time shorter forms are frequent measuring 0.75 

 by 1.5 microns. (Figures 10 and 11.) 



Spore formation. Spores are formed earljf appearing in 24 

 hours on plain agar. They form in the center or towards one 



