180 ATLAS OF BACTERIOLOGY. 



is suitable to the majority of bacteria. The addition 

 of milk sugar gives a milk-sugar nutrient medium 

 which is free from dextrose (Lehmannand Neumann). 

 B. Albuminous. 



1. Peptone water. In 1 litre of water are dissolved 

 10 gm. dried peptone, and 5 gm. sodium chloride, and 

 sterilized together. 



2. Milk. Fresh milk (best, fresh centrifugal milk) 

 is placed in test tubes and sterilized in the steam 

 chamber for one-half hour on two successive days. 

 Milk which contains the spores of the subtilis group 

 is often incapable of sterilization. 



3. Litmus whey (Petruschky). Casein is cau- 

 tiously precipitated from milk by giving it a very 

 feeble acid reaction with diluted hydrochloric acid, 

 the filtrate is boilefl and filtered, and the neutralized 

 fluid mixed with some litmus. This whey is not 

 easily prepared (vide Heim: "Lehrbuch," p. 210). 



4. Hay decoction. About 10 gm. dry hay are boiled 

 in a litre of water. The filtered solution is placed in 

 test tubes, and sterilized for two hours on three suc- 

 cessive days (kept over night in the incubating cham- 

 ber) in order to destroy the very resisting spores. 



5. Beer wort (not neutralized) is allowed, after 

 sterilization, to settle for a few weeks, then poured 

 off clear into test tubes, and again sterilized. 



6. Nutrient bouillon. 



(a) From meat : 500 gm. lean beef are boiled upon 

 the flame for one-half hour with l,000gm. of water in 

 an enamelled pot, filtered, the filtrate reduced to 1,000 

 gm. and 10 gm. peptone with 5 gm. sodium chloride 

 added; this is placed in the steam chamber until 

 dissolved, and the whole is then neutralized with 



