AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 289 



Potato. Thick, white, moist growth later becoming yellowish 

 brown. Never wrinkled or vermiform, rarely measley. Med- 

 ium discolored. 



Litmus milk. Acid production and coagulation, usually within 

 24 hours. The coagulum is at first firm but gradually undergoes 

 peptonization, and is usually completely dissolved at the end of 

 three weeks. Odor distinctly faecal and very disagreeable, with 

 a suggestion of indol. 



Blood serum. Thick, white growth. No hquefaction. 



Fermentation tubes. Glucose. Abundant growth in bowl ex- 

 tending up into closed arm which becomes turbid. Flocculent 

 precipitate forms but usually no scum. Reaction highly acid. 



Saccharose. Turbidity in bulb extending up into the closed 

 arm. Flocculent precipitate. No scum. Reaction highly acid. 



Lactose. Turbidity in bowl extending up into the closed arm. 

 No precipitate but usually a thick scum is formed. Reaction 

 highly acid. 



Thermal death point. Organisms have survived 1 hour in the 

 Arnold sterilizer and autoclaving to 15 pounds pressure. Killed 

 by 16 pounds pressure. 



Bacillus suhtilis (Ehrenberg) Cohn 



Synonyms. Vibrio subtilis Ehrenberg 1838; Bacillus suhtilis 

 Cohn 1872; Bacillus suhtilis (Ehrenberg) Cohn, Migula 1900. 



Considerable difference of opinion exists as to the correct in- 

 terpretation of the somewhat puzzhng literature concerning 

 this organism. In this paper we have followed the views of 

 Chester who has identified a number of organisms isolated in this 

 country as the real Bacillus suhtilis of Cohn, and who sent one of 

 his isolations to our laboratory several years ago. It is one of the 

 commonest organisms in milk, soil, dust and water. In mor- 

 phology it is one of the smallest of the aerobic spore-bearing 

 bacteria and is thus easily distinguished from Bacillus cereus 

 with w^hich it is most often confused. 



Morphology. Small, thin, homogeneous bacilli measuring 

 0.375 by l.o to 2.5 microns in 24 hour agar cultures. Some- 



