CULTURE METHODS 21 



Exercise 26. Production of £nz3mies 

 Jordan. General Bacteriology, p. 91. Philadelphia, 1908. 



Make two gelatin stab cultures of B. prodigiosus. Incubate 

 them below 22° C. until the bacteria have liquefied nearly all of 

 the gelatin. Add 1 cc. of toluol or 3 cc. of chloroform, shake 

 well, and filter after it has stood for fifteen minutes. Pour one 

 culture into a tube of sterile gelatin and the other into a tube 

 of milk, and note changes after three to five days. Why is the 

 disinfectant used instead of heat to kill the bacteria? Record 

 the results of adding these solutions to the gelatin and milk 

 tubes. 



SECTION VI 



FUNDAMENTAL METHODS USED IN THE CULTURE 

 OF BACTERLAi 



Exercise 27. Inoculation of Cultures on Solid Media 



Platinum needles mounted in glass rods are generally used 

 for inoculating cultures of bacteria. A straight needle is used 

 for stab and streak cultures, while a needle with a small loop 



o ( ~i 



-C 



Fig. 13. Inoculating needles 

 Pieces of platinum wire set in glass rods 



(diameter 2 mm.) at the extremity is used for liquid cultures 

 (Fig. 13). These needles are sterilized by puttmg them into 

 a gas flame and heating to redness just before and just after 



1 This section is intended to be a summary of methods most likely to he useful to 

 the undergraduate student or for a student beginning independent investigation. It 

 is not intended to be exhaustive. For more ample treatment of these subjects the 

 student is referred to Muir and Ritchie, Manual of Bacteriology ; Abbott, Principles 

 of Bacteriology ; Eyre, Bacteriological Technique ; Abel, Bakteriologisehes Taschen- 

 buch ; Lafar, Technisclie Mykologle ; and other special works. 



