284 SYNTHETIC CULTURE MEDIA 



would not grow when seeded in small numbers in a synthetic medium, but required 

 the presence of a growth stimulant, bios. For a summary of the literature on this 

 topic, the reader is referred to the excellent review by Tanner, Devereux, andHiggins.' 



For a synthetic medium to be wholly satisfactory, it should support growth when 

 continuous transfers of small inocula are made. 



Certain other difEculties are inherent in the preparation of synthetic media. Par- 

 ticular care must be used in most cases to adjust suitably the buffer content. In many 

 cases distilled water may prove troublesome, for traces of metal from containers may 

 exert a marked inhibitory action; in other cases they may stimulate growth. Distilled 

 water made from city supplies which are chlorinated may contain sufficient chlorine 

 to influence results markedly. In many cases it is necessary to guard against the toxic 

 effects of one ion by the addition of another which antagonizes it. A comprehensive 

 review of the influence of ions on microbial physiology has been given by Falk.^ 



'Tanner, F. W., Devereux, E. D., andHiggins, F. M.: /. Bad., 11,45-64. 1926. See also chap, 

 xxxvii in this volume. 



^ Falk, I. S.: Absi. Bad., 7, ^^i 87, 133. 1923. 



