OTHER INTESTINAL BACTERIA 213 



large sluggishly motile bacilli containing spores. A 

 gelatin stab culture made from these 24-hour liver broth 

 tubes will show after 48 hours incubation at 20° a dis- 

 tinct liquef}'ing anaerobic growth beginning about 2 

 cm. below the surface with gas bubbles at the top of the 

 liquefied area. In order to obtain absolutely pure 

 cultures it is necessary to fish from liver broth tubes 

 only 3-5 hours old as only young vegetative cells will 

 grow on plates. Transplants from the closed arm of 

 such tubes will grow on dextrose Uver agar plates incu- 

 bated under anaerobic conditions. 



Another method for isplating B. sporogenes suggested 

 by Wells is simpler than the foregoing. He recommends 

 the use of freshly-boiled lactose broth tubes (heated 

 in Arnold Sterilizer) brought to a temperature of 70 

 degrees C, at which temperature the inoculation is 

 made. The inoculated tubes are then kept at 70 

 degrees C. for 10 minutes and subsequently incubated 

 at 37 degrees C. By this means the spore forms of 

 B. sporogenes develop into vegetative cells in the course 

 of 24 hours and give rise to a rapid evolution of gas. 

 Aerobic plates made from these tubes will generally 

 give no growth. On the other hand, if B. coli were 

 present, gas would ordinarily be produced in 18 hours 

 and aerobic plates, either on litmus agar or Endo 

 medium would show an abundance of colonies. 



The organisms of the B. sporogenes group are large 

 stout bacilli often occurring in chains. They liquefy 

 gelatin vigorously and on agar produce fine discrete 

 gray colonies. They vigorously ferment dextrose, lac- 

 tose and saccharose, producing acid and gas, and in sugar 



