Preparation of Media 127 



The lists of glassware necessary for plating one 

 sample of milk and for preparing one liter of medium, 

 together with the necessary materials and apparatus, 

 are given at the end of this chapter, the actual amounts 

 being left to the discretion of the individual. They 

 may be readily secured from any firm dealing in such 

 materials. 



Some sort of an incubator is necessary. Very satis- 

 factory incubators are specially built for bacteriolog- 

 ical purposes, but, if it is necessary to economize, it 

 is possible to convert a poultry incubator for the pur- 

 pose, or a home-made incubator may be cheaply and 

 simply built by anyone with a little ingenuity. An 

 asbestos -lined box fitted with an electric light and 

 thermostat is very satisfactory. The one factor neces- 

 sary is a constant temperature of 37 C. or 98.6 F. 



Media. -It is possible to obtain agar or gelatine 

 already prepared from various bacteriological labora- 

 tories. If, however, it is found necessary to make 

 the medium, the following directions may be used: 

 As a basis for this medium use nutrient bouillon, or 

 broth. This may be made either from the ground 

 beef or beef extract. Directions for making the bouil- 

 lon from ground beef are found in Moore's Laboratory 

 Directions for Beginners in Bacteriology. It is much 

 easier to use beef extract and, for general purposes, 

 entirely satisfactory. 



Measure out the following: 



Water 1 liter 



Liebig's Extract of Beef . . . 3 grams 



Peptone (Wittes) 10 grams 



