8 LABORATORY BACTERIOLOGY 



11. Work for this exercise. Make looo cc. of bouillon and 

 distribute it as follows : 



Put 5 cc. in each of lo small sterile test tubes. 



Put 300 cc. in each of 2 large (500 cc.) Erlenmeyer flasks, 

 and the remainder in a third flask. 



Put 5 cc. of distilled water in each of 5 small sterile test 

 tubes and sterilize them with the bouillon. (They are to be 

 used subsequently in place of bouillon in making dilutions.) 

 Label the tubes " sterile distilled water.'' All media required 

 to carry out the directions will be furnished by the instructor 

 excepting such as the student is directed to make in Exercises 

 III, IV, and X. 



12. The preparation of bouillon. Take 500 grams of lean 

 beef, remove all fat, and grind it in a sausage machine or have 

 it minced at the butcher shop. Place the minced meat in an 

 agate-iron dish, add 1000 cc. (2 parts water to one of meat) 

 of clear boiled water, cooled to 65° C, and stir thoroughly 

 with a glass rod. Then macerate it, with frequent stirring, in 

 a water bath at a temperature of 60° C. for one hour after the 

 temperature of the meat and water reaches that of the water 

 outside or, to save time, at a temperature of 65° C. for 30 

 minutes. Remove the meat by straining the liquid through a 

 piece of cheese cloth. For this a stout iron meat press is 

 desirable. Boil the strained meat infusion for 20 minutes. "^ Cool 

 to harden the fat, and filter through filter paper. The filtrate 

 should equal in quantity the amount of water used ; if it does 

 not, add enough distilled or clear boiled water to make up that 

 amount. To this meat infusion add i % peptone (Witte's) 

 and -^^ sodium chloride. Add enough of a normal solution 

 of sodium hydrate to give the liquid a faintly alkaline reaction 

 when litmus is used as an indicator. (For method of titrating 

 media, see § 14.) The infusion is then boiled in a water bath 



^ In case of a short period, the exercise may be divided at this point 

 by boiling the infusion for 30 minutes and keeping it overnight. The 

 receptacle should be covered. ' 



