258 



CHEN CHONG CHEN AND LEO F. RETTGER 



a sorting out process was conducted. All tubes which failed to 

 show gas production by the end of the fifth day were discarded. 

 The tubes which contained gas were further plated on plain agar, 

 for the purpose of more complete isolation or verification of purity 

 of the cultures. Stock cultures were finally made from well-iso- 

 lated colonies. 



SOURCES OF SAMPLES 



NUMBER OF 

 SAMPLES 



NUMBER OF 

 SAMPLES YIELD- 

 ING COLI-LIKE 

 COLONIES 



NUMBER OF CULTURES 

 FROM POSITIVE SAMPLES 



Aerogenes 

 type 



Coli type 



Soils 



Feces 



Human (7) . . . 

 Monkeys (2). 

 Horses (4) . . . 



Cows (3) 



Sheep (4).... 

 Fowls (3) . . . . 



Total 



7 

 2 

 4 

 3 

 4 

 3 



23 



20 



173 



