THE COLON GROUP OF BACILLI 



131 



COMPARATIVE RESULTS OF ORDINARY AND SYNTHETIC 

 AGAR MEDIA 



(Dolt, 1908) 



The Use of Liver Broth for the Isolation of a Maximiim 

 Proportion of Gas-forming Bacteria. The media we 

 have been discussing, phenol broth, dextrose broth 

 incubated at 46°, and bile, are designed to cut down 

 the gas producers which appear in ordinary dextrose 

 broth so that only vigorous topical members of the 

 colon group are able to develop. For special research 

 purposes when it is desired to get the largest possible 

 proportion of gas formers of all kinds, there are other 

 media which give even more positive fermentation 

 results than dextrose broth itself. The most important 

 of these is the liver broth of Jackson and Muer (191 1) 

 made up with beef liver, peptone, dextrose and potas- 

 sium-acid-phosphate. The Committee on Standard 

 Methods of Water Analysis (191 2) recommends that 

 if "a study of all gas-forming bacteria, including 

 attenuated forms, is desirable, then liver broth should 

 be employed in preference to the usual dextrose broth, 

 as it gives a larger number of attenuated forms, has 

 better rejuvenating power, and gives fewer anomalies 

 and greater and more rapid gas production." In 

 order to avoid attenuation or inhibition transplants 



