SOLID TRANSPARENT MEDIA 6 1 



potatoes are mashed and pressed through a fine cloth. The 

 juice is allowed to settle, is filtered, and after one hour's cook- 

 ing has added to it 10 per cent, gelatin; then 2\ c.c. y L normal 

 sodium hydroxid solution, and finally i per cent, potassium 

 iodid. 



Typhoid Medium of Hiss. This consists of a slightly acid 

 mixture of gelatin and agar, beef-extract, sodium chlorid, and 

 dextrose, used in different proportions for plate and tube cul- 

 tures. It is semisolid in character, and facilitates the identi- 

 fication of the motile typhoid bacilli, which produce a uniform 

 clouding through the medium in tubes. 



Bile-salt Media (MacConkey). Used for intestinal bac- 

 teria; stock solution consists of: 



Sodium taurocholate 0.5 gm. 



Witte's peptone 2.0 



Distilled water 100.0 c.c. M. 



To which is added as an indicator, neutral red (crimson 

 with acid, yellow with an alkali) in i per cent, solution, 0.5 c.c., 

 and dextrose or lactose. The fluid is placed in fermentation 

 tubes and sterilized for ten minutes on three successive days. 



Agar can be added to make bile-salt lactose agar. Bacillus 

 coli and Bacillus typhosus grow readily on this media; other 

 water bacteria are inhibited, especially at 40 C.; acid-formers 

 and gas-formers are denoted by rose-red-colored colonies. 



Milk Culture-medium. The milk used should be fresh 

 and should be placed on ice for eight to ten hours to allow the 

 cream to rise; the skimmed milk is siphoned off into flasks 

 or tubes and sterilized for three successive days. Litmus is 

 often added, or sterile i per cent, azolitmin solution. 



Urine Media (for Gonococci) : 



Urine (sterile taken) i part. 



2 per cent, agar solution i 



Fresh Egg Cultures (After Hueppe). The eggs in the 

 shell are carefully cleaned, washed with sublimate, and dried 

 with cotton. 



