6 



GENERAL BACTERIOLOGY 



Special Diebctions. All glassware prepared in 1. is to be 

 sterilized for one hour at 150° C. The small pipettes should be 

 placed in brass tubes, provided for the purpose, and also sterilized. 



EXERCISE 4. PEEPAEATION OP BOUILLON. 



General Directions. Any one of the three methods (A, B 

 or C ) may be used. They are arranged in order of preference, but 

 method C is the most convenient, and hence most used. 



A. 

 o. rrom 500 grains (1% lbs.) of lean 

 beef remove the fat and connective tis- 

 sue and mince (or use Hamburg steak). 



h. Add 1 liter of distilled water and 

 after shaking thoroughly set in ice 

 chest for 12 to 24 hours. 



c. Squeeze through a cloth and add 

 enough distilled water to filtrate to 

 make 1 liter and place in vessel to cook. 



d. Add to any of the above solutions: 1% (10 gms.) peptone 

 (Witte) and %% (5 gms.) common salt (NaCl), then v^eigh solu- 

 tion, with vessel, so that the water which is subsequently driven 

 oif in cooking can be accurately replaced. 



Cooking may be done either in a flask which is heated in a water- 

 bath or sterilizer, double- walled boiler, or rice-cooker. In case a rice- 

 cooker is used a 50% solution of calcium chloride should be placed 

 in the outer vessel instead of water as by this means the contents 

 of the inner vessel can be brought to a rapid ebullition, something 

 impossible by the use of water alone. 



e. Heat, not above 60° C, until ingredients are in solution, 

 then restore the water lost by evaporation. 



/. Neutralize. This is a very important step and calls for great 

 care. Of the following methods, A is more accurate and should 

 be employed for special or research work. For ordinary routine 

 work B may be emploj^ed. 



