AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 497 



Broth. Granular scum ^nd flocculent growth which soon set- 

 tles to the bottom. 



Peptone. Similar granular scum and flocculent sediment. 



Potato. Viscous yellowish-gray growth spreading profusely 

 and rapidly over the whole medium. 



Litmus milk. Reaction highly acid within 24 hours and a firm 

 coagulation within 48 hours. Peptonization soon begins and 

 proceeds very slowly eventually converting the coagulum to an 

 amber-colored fluid. Coagulation is more rapid in freshly iso- 

 lated strains. 



Blood serum. Profuse moist dull interlacing or mycelioid 

 growth. No peptonization. 



Fermentation tubes. Glucose : a flocculent growth in the bowl 

 and a granular scum. Turbidity in closed arm. Reaction acid. 



Saccharose: a flocculent growth in the bowl with an acid reac- 

 tion. Arm usually clear. 



Lactose: a similar flocculent growth with an acid reaction. 

 Arm usually clear. 



Thermal death point. Spores survive 12 pounds in the auto- 

 clave but are killed by 15 pounds. In the Arnold they survive 

 45 minutes but are destroyed by an hour's exposure. 



Bacillus mesentericus variety flavus nov. var. 



This is a new variety of Bacillus mesentericus to which the 

 name flavus is given because of the abundant yellow pigment it 

 produces. We have encountered it repeatedly in dust and in 



soil. 



Morphology. Thin homogeneous rods with round ends, in 

 young cultures on plain agar measuring 0.375 to 0.5 by 1.5 to 

 4 microns. On glucose agar the organisms are a little thicker 

 and longer, measuring 0.5 to 0.75 by 3 to 5 microns. They of- 

 ten grow in long threads measuring 9 to 12 microns in length. 

 Shadow forms are formed early both on plain and on glucose agar. 

 In old cultures especially on glucose agar the long forms tend to 

 curve. (Figures 55, 56 and 57.) 



Motility. Actively motile in young cultures. 



