GROWTH OF BACTERIA IN PROTEIN-FREE PRODUCTS 229 



grew as well or better in opsine than in Witte's peptone. The 

 cultural characters on the two media were in general the same. 



With the exception of the diphtheria group, the different organ- 

 isms remained viable as long on opsine as on the standard peptone- 

 meat-infusion medium. 



A reaction slightly alkaline to litmus was found to be the best 

 for general use. Glycerol increased the growths in alkaline but 

 not in acid media, while glucose seemed as a rule to be somewhat 

 detrimental. Prepared meat extract, and better still, fresh beef 

 infusion, were distinctly favorable. Decolorization with animal 

 charcoal slightly lessened the value of the opsine as a culture 

 medium. 



The decomposition products of casein, lactalbumin and edestin 

 obtained by acid hydrolysis were also employed as culture media. 

 Of these the hydrolyzed casein gave the best results, but it was 

 inferior to the opsine. The edestin product was the least satis- 

 factory. It is highly probable that in the hydrolysis of these 

 proteins with hydrochloric acid the treatment is sufficient to 

 destroy many of the intermediate decomposition products which 

 serve so admirably as food for microorganisms. 



Bacteria do not require proteins, even in minute quantities, to 

 carry on their normal cultural development, but obtain their 

 sustenance from less complex substances, as for example the amino 

 acids and perhaps some of the simpler polypeptids. 



In conclusion we desire to express our sincere gratitude to 

 Prof. Lafayette B. Mendel for the preparation of the different 

 acid-digestion products employed in this investigation, and for 

 his hearty cooperation throughout the entire course of this work. 



REFERENCES 



Dalimier, R. et Lancereaux, E. 1913 Le milieu de culture d'acides amines 

 complets pour les microorganismes. Presse Med., 21, 419: Les pro- 

 duits de la proteolyse naturelle et totale comme milieu de culture 

 pour les microorganismes, Arch, de m^d. exper. et d'anat. path., 25, 

 449-68. 



