STANDARD MEDIA 79 



differential colonies (20° C. and 37° C), red colonies and total 

 colonies, etc. 



6. Lactose Bile. — This medium is to be made in two ways: 

 Add I per cent, of peptone and i per cent, of lactose to sterilized 

 undiluted fresh ox gall; or add the peptone and lactose to a 10 

 per cent, aqueous solution of freshly made dry ox gall. It is used 

 without titrating. Old dried ox gall should not be used. Obtain 

 it from a reliable dealer. If possible, make arrangements to get 

 the fresh undiluted ox gall from some abattoir. 



This is the standard medium for making the quantitative as 

 well as qualitative tests for the colon group of bacilli. 



7. Liver Broth. — Chop 500 grams of fresh beef liver into small 

 pieces and place in 1000 cc. of distilled water. Weigh infusion 

 and container. Boil for 2 hr. in rice cooker, starting cold 

 and stirring occasionally. Make up loss in weight and pass 

 through wire or cloth strainer. Add 10 grams of peptone, 10 

 grams of dextrose and i gram of di-potassium phosphate (K2- 

 HPO4) . Dissolve the added ingredients by warming in rice cooker 

 with stirring and then titrate to the neutral point (to phenol- 

 phthalein). Boil for 30 min. in the rice cooker and for 5 min. 

 over open flame with constant stirring to prevent the carameliza- 

 tion of the dextrose. Make up loss due to evaporation and filter. 

 Tube, sterilize and store as for other media. 



This is a much used enriching medium which gives asg forma- 

 tion with all of the species which ferment dextrose. It is also 

 much used to rejuvenate pure cultures of bacteria and encourages 

 the development of attenuated forms of bacteria. 



8. HissTyphoidBacillusMediiun.^ — Two media are used. One 

 for the isolation of the typhoid bacillus by the plating method, and 

 the other for the differentiation of the typhoid germ from other 

 forms in tube cultures. The former is designated as the plate 

 medium and the second as the tube medium. They are prepared 

 as follows: 



