178 CULTURE MEDIA 



Polyatomic alcohols Trihydric, Glycerin. 



Tetrahydric, Erythrite. 



Pentahydric, Adonite 



Hexahydric, Dulcite, (dulcitol or mel- 

 ampitite) , isodulcite (rhamnose) , rnan- 

 nite (mannitol), sorbite (sorbitol), 

 inosite. 



These substances should be obtained from Kahlbaum 

 (of Berlin); in the pure form, and when possible 

 as large crystals, and the method of preparing a 

 medium containing either of them may be exem- 

 plified by describing Dextrose Solution. 



Dextrose Solution. 



1. Weigh out 



Peptone 20 grammes 



Glucose 10 grammes 



and grind together in a mortar ; then emulsify in 100 c.c. 

 of distilled water heated to 60 C. 



2. Place in a flask and add 



Distilled water 850 c.c. 



3. Steam in the steamer at 100 C. for twenty 

 minutes to dissolve the peptone and glucose. 



4. Add 



Kubel-Tiemann litmus solution (Kahlbaum) . . . 50 c.c. 



(The substances enumerated above react acid to 

 phenolphthalein, but variously toward the neutral 

 litmus solution. To such as react acid, add very 

 cautiously sodium hydrate solution to the medium 

 in bulk until the neutral tint has returned) . 



5. Fill into tubes in which have previously been 

 placed the inverted Durham's gas tubes. 



6. Sterilise in the steamer at 100 C. for twenty 

 minutes on each of three successive days. 



NOTE. On no account should these media be sterilised in the 

 autoclave, as temperatures above 100 C. themselves induce 

 hydrolytic changes in the substances in question. It is equally 



