Isolation of the Colon Bacillus. 107 



Opposite the words " Preliminary fermentation tube " 

 are recorded by plus or minus signs the results of the first 

 enrichment test in the five or ten tubes inoculated. Under 

 the columns headed by plus signs the presence or absence 

 of typical red colonies on the litmus-lactose-agar plate is 

 similarly indicated. The third line serves for the results 

 of the microscopic and macroscopic appearance of the 

 agar streak. If this gives the proper t3^e of growth and 

 rod-shaped organisms are found, a dextrose fermentation 

 tube, a nitrate tube, a milk tube, a peptone tube, and a 

 gelatin stab are inoculated from it. 



After forty-eight hours incubation at 37 degrees, the 

 dextrose iDroth and milk tubes are examined and the 

 results recorded in the proper columns by plus and minus 

 signs. The amount of gas in the closed arm of the dex- 

 trose tube may be conveniently measured by the Frost 

 gasometer (Frost, igoi). If a measurement of the gas 

 ratio is desired a few centimeters of strong sodium or 

 potassium hydrate are added and mixed with the broth 

 by cautiously tipping the tube; a second measurement 

 determines the amount of gas absorbed (assumed to' be 

 CO2). The gas should first fill from one-third to two- 

 thirds of the closed arm, and about one-third of the total 

 amount should be absorbed. ' 



The milk tube is tested by heating to boiling over the 

 free flame; if coagulation occurs the test is considered 

 positive. 



After ninety-six hours incubation at 37 degrees the 



