148 C. J. T. DORYLAND 



Ammonia-acetate solution 



Prepare a N/0.2578 solution of NaOH and a N/0.6205 solu- 

 tion of KOH. Mix these solutions in equal proportions and 

 substitute in the place of the silicate solution. The procedure 

 from here on is the same as for the silicate medium. 



Results with pure cultures 



It has been the object in working with these media to test 

 as many pure cultures of microorganisms upon each medium 

 as could be obtained. In this way we shall be able eventually 

 to determine all the compounds which each organism can use 

 as a source of energy as well as those from which it can obtam 

 its nitrogen. This will eventually enable us to group the known 

 organisms (yeast and molds as well as bacteria) according to 

 their ability to utihze energy material of a given chemical struc- 

 ture and configuration. The same thing applies to their nitro- 

 gen requirements. When this has been accomplished we may 

 then eliminate all media suggested in the above groups that are 

 common to a given group of organisms and retain for practical 

 use the one which is the most serviceable. Thus eventuall}^ 

 the above group of synthetic media will be reduced for general 

 use to a few which are mutually inclusive and exclusive with 

 occasional employment of others for special studies. 



Several of the media described above have been tested upon 

 225 pure cultures of bacteria, 50 cultures of molds and 6 cultures 

 of yeast. In the following table will be found the positive re- 

 sults obtained from three glucose media and three acetate media ; 

 only positive results are given because of lack of space. 



Out of 225 pure cultures of bacteria tested the following re- 

 sults were obtained: On the glucose-ammonia medium there 

 were 83 positive growths; on the glucose-nitrate medium 70 

 positive growths; on the acetate-ammonia medium 25 positive 

 growths; and on the acetate-nitrate medium 17 positive growths. 

 With the glucose-cyanide medium there were 7 positive growths ; 

 and with the acetate-cyanide medium there were 2 positive 

 growths. 



