PRELIMINARY REPORT ON SYNTHETIC MEDIA^ 



C. J. T. DORYLAND 

 North Dakota Experiment Station, Fargo, North Dakota 



THEORETICAL DISCUSSION 



By a "Synthetic Medium" is meant a solution which con- 

 tains only compounds of known composition and structure. 

 Any medium which includes compounds of unknown composi- 

 tion or structure is not a synthetic medium. This paper deals 

 both with synthetic nutrient solutions, and, with solid synthetic 

 media formed by the precipitation of an agglutinant from com- 

 pounds of known composition and structure. In the latter 

 case, the agglutinant formed by precipitation from known 

 compounds should have a known structure and composition. 

 We should properly exclude from the list of synthetic media 

 all those which contain substances of unknown composition 

 or structure, such as meat extracts, proteins of unknown struc- 

 ture, agar and gelatine. In order, however, to illustrate the 

 present conception of possible media, the scheme presented 

 includes many compounds of unknown composition and struc- 

 ture, such as the polysaccharids, tannins, glucosides and pro- 

 teins. These compounds which have either an unknown com- 

 position or unknown structure are placed in their logical posi- 

 tion in the systematic arrangement, because their decomposi- 

 tion products are more or less known and because in nature 

 they, or their decomposition products, furnish the principal 

 source of energy to saprophytic microorganisms, and because 

 it may be necessary to fall back upon some of them in order to 

 secure media for such microorganisms as cannot utilize media 

 made of sunpler compounds. However, media which con- 

 tain such compounds of unknown composition or structure 

 cannot properly be classed as synthetic. 



' Presented at Seventeenth Annual meeting of the Society of American Bac- 

 teriologists, Ilrbana, Illinois, December 28, 1915. 



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