204 Appendix. 



Sodium chloride shall not be added to any culture 

 medium herein specified. 



Pepton shall be that of Witte (dry from meat). 



Gelatin shall be the best French brand, so-called. It 

 shall be as free as possible from acids and other impuri- 

 ties, and shall be of such a character that a lo per cent 

 solution prepared in the usual way shall not soften when 

 kept at a temperature of 25° C. 



Commercial agar in threads shall be of as high a 

 grade as can be obtained. Agar may be purified by 

 washing. 



The various sugars, such as dextrose, lactose, and sac- 

 charose, shall be as nearly as possible the chemically 

 pure compounds designated. Unusual efifort to obtain 

 such sugars is considered to be necessary. 



Glycerine shall be double distilled. 



In place of litmus, azolitmin* shall be used as a i per 

 cent aqueous solution. 



Of the various other ingredients used, nearly all of 

 which are of a mineral nature, special effort shall be 

 made to see that they are chemically pure products within 

 the full meaning of this expression. 



STERILIZATION. 



Of the two available methods of sterilization, the inter- 

 mittent method at a temperature of 100° C. is considered 

 on the whole to be preferable. The higher temperatures 



* Preferably Kahlbaum's (authors). 



