76 BACTERIOLOGICAL METHODS 



Furthermore, the reasons why the special media are used should 

 be clearly set forth, so that co-workers may judge of their special 

 value and may try them out intelligently, should they care to 

 do so. 



As special media are adopted into general use by the majority 

 of bacteriologists they are to be relegated into the group of general 

 media. For example, a few years ago, lactose-litmus-agar, Endo 

 medium, Hess' medium, lactose-bile medium, etc., were special 

 media. They are now in general use and they should be pre- 

 pared according to a standard method. We hereby give the 

 methods of preparing some of the more important media used in 

 general bacteriological work, following the directions of the 

 Committee of the A. H. A. 



I. Nutrient Broth. — Infuse 500 grams of chopped lean meat 

 for 24 hr. in distilled water. Shake occasionally and keep in 

 the refrigerator. Any loss by evaporation is to be restored. 

 Strain the infusion through cotton or through cotton flannel. 

 Add I per cent, of peptone and warm over water bath or steam 

 until the peptone is entirely dissolved. Heat for 30 min. in 

 rice cooker or in steam sterilizer and restore any loss by evapora- 

 tion. Titrate with normal sodic hydrate (or normal hydro- 

 chloric acid) to a reaction of -f- i.o per cent. Boil for 2 min. 

 over open flame, stirring constantly. Restore loss by evapora- 

 tion. Filter through cotton (placing the cotton on cotton 

 flannel or on perforated filter paper). Pass the medium through 

 this filter until it comes out perfectly clear. Again titrate and 

 record the final reaction. Pour into tubes (10 cc. in each tube) 

 and sterilize in the manner as already directed. 



This medium is much used for general cultural purposes. 

 It is used in making the cultures of typhoid fever germs, for 

 determining the phenol coefficient of disinfectants by the Ander- 

 son-McClintic method of rating the germ destroying power of 

 disinfectants. It is also used in culturing motile bacteria, etc. 

 Variousjndicators may be added. 



