APPENDIX 273 



when incubated at 37 C. Such tests are sometimes used 

 in the control of nitration plants. 



LIVER BROTH 



This medium is made from a hot infusion of beef liver 

 instead of fresh meat, and is, in other respects, with the 

 exception that phosphate is added the same as dextrose 

 broth, but it is a richer food medium for bacteria. It 

 gives gas formation with all species which ferment dextrose 

 and develops attenuated bacteria, whether gas-forming or 

 not, to a better degree than does beef broth. It is also 

 especially suited to the rejuvenation of species in pure 

 culture. 



FORMULA 



Beef Liver 500 gm. 



Peptone (Witte's) 10 gm. 



Dextrose 10 gm. 



Di-Potassium Phosphate (K^HPO-i) i gm. 



Water 1000 gm. 



1. Chop 500 gm. of beef liver into small pieces and add 

 1000 c.c. of distilled water. Weigh the infusion and container. 



2. Boil slowly for 2 hours in a double boiler, starting 

 cold and stirring occasionally. 



3. Make up any loss in weight by evaporation and pass 

 through a wire strainer. 



4. To the filtrate add 10 gm. of peptone, 10 gm. of 

 dextrose and i gm. of potassium phosphate. 



5. After warming this mixture in a double boiler and 

 stirring it for a few minutes to dissolve the ingredients, 

 titrate with N/2O sodium hydrate, using phenolphthalein as 

 an indicator, and neutralize with normal sodium hydrate. 



6. Boil vigorously for 30 minutes in a double boiler, 

 and 5 minutes over a free flame with constant stirring to 

 prevent the caramelization of the dextrose. 



7. Make up the loss in weight by evaporation and filter 

 through cotton flannel and filter paper. 



