60 ESSENTIALS OF BACTERIOLOGY 



Human blood-serum derived from placenta, serum from 

 ascitic fluid and ovarian cysts, is prepared in a similar 

 manner to the above. 



Blood coagulum, suggested by the author, is the blood itself 

 (not the serum only) coagulated in test-tubes. It is dark brown 

 in color and allows some colonies of bacteria to be more visible. 

 It requires less time to prepare, and is not so likely to become 

 contaminated as when the serum is used. 



L6 filer's Blood-serum Mixture. See p. 124. 



Peptone Solution (Dunham's) . Sodium chlorid, 0.5 parts; 

 peptone, i part; water, 100 parts. Boil, filter, and sterilize. 

 Useful to detect presence of indol. 



Other Nutrient Media. Milk, urine, decoctions of various 

 fruits and plants, and for cultivating anaerobic bacteria, eggs. 



Lactose (or Dextrose) Litmus-agar (for Water Bacteria). 

 To nutrient agar, i per cent, of dextrose or lactose is added 

 just before sterilization. The reaction should be neutral to 

 phenolphthalein. Then, if the medium is to be used in tubes, 

 sterilized azolitmin, i per cent, (aqueous solution) is added 

 just before the final sterilization. If Petri dishes are used, 

 the azolitmin solution is not added until the medium is ready 

 to be poured. 



Blood-agar. Human or other blood is obtained direct 

 from the body under strict aseptic conditions, and a few drops 

 smeared over the surface of agar in tubes or plates. These are 

 then placed in the incubator for a few days, and the contami- 

 nated ones are rejected. This media is used for influenza bacilli 

 and gonococci. 



Dunham's rosalic acid solution consists of the following: 



Peptone solution (Dunham) 100 c.c. 



2 per cent, solution rosalic acid 0.5 gm. 



Alcohol (80 per cent.) 100 c.c. M. 



To detect acids and alkalis. 



Eisner's Medium (for Typhoid) (Potassium lodid 

 Potato -gelatin). Five hundred" grams of peeled and washed 



