APPENDIX 279 



(i per cent peptone in water) is recommended for use in 

 the indol test. 



-ESCULm MEDIA 



Broth. Dissolve lo gm. peptone, 5 gm. commercial 

 sodium taurocholate (or glycocholate), o.i gm. aesculin and 

 0.5 gm. soluble iron citrate in i liter distilled water. 



Tube in 5 c.c. quantities in test-tubes and sterilize. 



It is preferable to keep the iron citrate solution separate 

 and to add it to the rest of the media. as used, since the 

 iron causes a precipitate. Sometimes the iron citrate will 

 not readily dissolve. In such case a few drops of ammonia 

 will cause immediate solution, especially on warming. The 

 excess of ammonia should then be boiled oflF. 



Agar. This medium is made in the same manner as the 

 broth with the addition of the usual amount of agar. 



APPARATUS 



Few definite requirements need be made respecting 

 apparatus. The quaUty of the glass shall be such as not 

 to be easily acted upon by the reagents used, and all glass- 

 ware shall be scrupulously clean when used. When nec- 

 essary it shall be steriUzed by dry heat for one hour at 

 about 150° C. A slight bro\N-ning of the cotton stoppers, 

 is a good index of proper exposure. 



In some operations, as for example, the determination 

 of the thermal death point, it is necessar}' to use test-tubes 

 of a definite size and thickness. For this purpose the 

 standard size culture tube shall be 15 cm. long, 1.6 cm. 

 in diameter, and of medium weight. Tubes to be filled 

 with gelatin for quantitative work may be those described 

 as 6 in. X I in. " heavy." 



The standard loop for making transfers shall be pre- 

 pared as follows: 



