Ill 



The presence of fermenting organisms, including B. coli is shown when 

 the medium turns red (due to acid production) and gas is formed in the 

 inner tube. 



D. Glucose Broth. Same as lactose broth, substituting glucose for 

 the disaccharid. 



E. Liver Broth. (After Prescott and Winslow). 1. 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 10 gm. 



Dextrose 10 gm. 



Di-Potassium Phosphate (K 9 HP0 4 ) 1 gm. 



Water . ' 1000 gm. 



2. Chop 500 gm. of beef liver into small pieces and add 1000 c. c. 

 of distilled water. Weigh the infusion and container. 



3. Boil slowly for 2 hours in a double boiler, starting cold and stir- 

 ring occasionally. 



4. Make up any loss in weight by evaporation and pass through a 

 wire strainer. 



5. To the nitrate add 10 gm. of peptone, 10 gm. of dextrose and 1 

 gm. of potassium phosphate. 



6. After warming this mixture in a double boiler and stirring it for 

 a few minutes to dissolve the ingredients, titrate with N/20 sodium 

 hydrate, using phenolphthalein as an indicator, and neutralize with normal 

 sodium hydrate. 



7. 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. 



8. Make up the loss in weight by evaporation and filter through 

 cotton flannel and filter paper. 



9. Tube and sterilize in an autoclave for 15 minutes at 120 C. (15 

 pounds). 



The following media have been suggested for the elimination of spur- 

 ious presumptive test: 



F. Gentian Violet Lactose Broth. (Hall and Ellefson). The 

 medium consists of 1 percent lactose broth containing 1-20,000 gentian vio- 

 let. 



