358 APPENDIX 



digest over a free flame, weigh again and make up any loss 

 with distilled water. 



3. To the hot agar add the peptone and lactose and mix 

 until dissolved; then add the strained meat infusion. 



4. Titrate and adjust the reaction to 0. 



5. Add the azolitmin, boil up over the free flame and 

 place about 100 c.c. in sterile 250 c.c. Florence flasks. 



Each student will need four litmus lactose agar shakes. 



II. Litmus lactose agar. (To be used in tubes for plat- 

 ing only.) 



1.5% agar. 



1 . 0% peptone. 



1.0% lactose. 



2 . 0% azolitmin solution. 



500 c.c. meat infusion. 



500 c.c. distilled water. 



Method. 1. This agar is prepared as ordinary nutrient 

 agar making the reaction +10, adding the lactose and azo- 

 litmin just before tubing. 



2. Tube and sterilize by the Tyndall method. 



Each student will need at least forty tubes of litmus lactose 

 agar. 



III. Gelatin. 



15% gelatin. 



1% peptone. 

 500 c.c. meat infusion. 

 500 c.c. distilled water. 



Method. Prepare, tube and sterilize as for ordinary 

 gelatin. 



Salt is omitted. Reaction +10. 



Each student will need forty or fifty tubes of salt-free gela- 

 tin. 



IV. Sugar-free broths and sugar broths. (Neutral red 

 dextrose broth.) 



