ISOLATION OF THE COLON BACILLUS. 73 



the results obtained at Lawrence during a period of 

 eighteen months. 



It should be noted that considerable differences often 

 appear in these biochemical reactions between tubes of 

 the same batch of a medium, inoculated with approxi- 

 mately the same amount of the same culture. This has 

 been shown very markedly for the amount of the gas and 

 the proportion of carbon dioxide in the dextrose tube by 

 Fuller and Johnson (Fuller and Johnson, 1899), Penning- 

 ton and Kiisel (Pennington and Kiisel, 1900), Gage 

 (Gage, 1902), and one of ourselves (Winslow, 1903). 

 Variations in the nitrate reduction are often even more 

 marked, one tube, perhaps, showing a strong reaction 

 and another none. In important cases, therefore, it is 

 desirable to inoculate the subcultures in duplicate. 



