GENERAL BACTERIOLOGY 
95 
With these substances as a basis, many so-called “ enrich¬ 
ing’ ’ substances may be added, in order to enable us to 
grow the bacteria which require especially rich food¬ 
stuffs ; of such fastidious bacteria we may mention 
pneumococci, streptococci, gonococci, influenza bacilli, 
etc. Of the 11 enriching ’ ’ substances those most frequently 
used are various sugars, blood (either whole or “whipped” 
—defibrinated in order to prevent the coagulation), as- 
Fig. 18.—Making a transfer of a culture. 
citic fluid (the fluid removed from the patients suffer¬ 
ing from dropsy), etc. 
Speaking generally, the following requirements con¬ 
cerning the general nature of the ingredients used in 
preparing the culture media should be borne in mind: 
1. Distilled water should be used unless tap water is 
specified. 
2. All chemicals used should be of the highest grade 
obtainable (the so-called “chemically pure,” C. P.) 
