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XVI INTRODUCTION / 



conjunction with a specific name, the latter including the chief nitrogen and 

 carbon source, where possible, and the name of the author who first listed the 

 medium. Thus "273 Ayers' Glucose Ammonium Phosphate Solution," indi- 

 cates that Ayers first described the medium, the nitrogen source was ammonia, 

 the carbon source glucose, and that the medium is No. 273 in this collection. 



In addition to the carbon and nitrogen source the nature of the solidifying 

 agent is also employed in naming culture media, as, for example, "1553 Greig 

 Smith's Sucrose Peptone Agar." 



Where the original article containing a medium was not available the fact is 

 indicated by placing the author from whose publication the medium was ob- 

 tained in parentheses after the name of the medium. Thus "2156 Beck's 

 Glycerol Serum Agar (Klimmer)" indicates that the medium was obtained from 

 Klimmer who referred to Beck as the author. 



If the same medium is described by different authors, only the earliest avail- 

 able author's name appears in the medium name, but the other authors are given 

 under the heading "references" at the end of the description of the medium. 



Where several media differ only with respect to the relative quantities of 

 constituents employed, or in the method of preparation, the earliest described 

 medium takes precedence, and all others are described as variants. 



One of the vexing questions which arose was that of the disposition of media 

 in which it was specified that a number of substances might be substituted for 

 each other. For example, if the availability of various carbon sources is being 

 studied, shall each new combination, as the employment of glucose, sucrose, 

 glycerol, etc., be considered a distinct medium? To do so would have markedly 

 extended the number of media to be considered. 



The term "basal" was introduced to take care of this situation. This was ap- 

 plied to the formula exclusive of the substituted constituents which then became 

 added nutrients. The term "basal" occurring in the name of a medium there- 

 fore designates that the formula is not in iteslf a complete medium, but that it 

 serves as a base to which other constituents are added. 



A serious difficulty in naming media arose in connection with the use of beef 

 extracts and meat infusions. This was particularly troublesome when authors 

 did not specify whether extract or infusions were employed. Where the use of 

 extracts was specified in the articles reviewed, these terms appear in the names 

 of the respective media, as e.g., "779 Dunham's Infusion Broth" or "1695 

 Heinemann's Meat Extract Agar." Where the author did not specify the 

 nature of the material employed (i.e., whether extract or infusion) the term 

 "bouillon" is employed, thus "936 Kendall, Day and Walker's Mannitol 

 Bouillon." 



