210 HAROLD C. ROBINSON AND LEO F. RETTGER 



Apparently the first protein-free medium which compared 

 favorably with the universally-used peptone medium was the 

 opsine studied by Dalimier and Lancereaux (1913). Their paper 

 is very suggestive, and in a large measure served as the inspira- 

 tion and point of departure of the present investigation. 



Opsine is a biuret-free product resulting from the combined 

 action of trypsin, erepsin and pepsin on certain protein materials, 

 not named by the authors or manufacturers. ^ It contains the 

 amino acids of the hydrolyzed proteins, also nucleic acid and 

 glucosamine, or their decomposition products. Phosphorus 

 would presumably be present in the nuclein and sulphur in the 

 cystine. The opsine gave a high formol titration for monamino 

 acids. Leucine and tyrosine were detected by their crystals, 

 and tryptophane by the bromine water test. The biuret test 

 for protein was always negative. On this basic medium, with 

 the addition of glycerol and agar, Dalimier and Lancereaux, 

 successfully cultivated not only the more common pathogens 

 and non-pathogens, but also such delicate organisms as the 

 pneumococcus, gonococcus, meningococcus, B. diphtheriae, B. 

 tetani and B. tuberculosis (human, bovine and avian types). 

 These were all carried through several transplants, without any 

 apparent loss of viability. When injected into animals, sterile 

 opsine had no injurious effect. 



EXPERIMENTAL 



In the present investigation numerous cultural tests were made 

 with opsine as the chief and, as a rule, the only source of nitrogen 

 in the medium. Cultural studies were also carried on with 

 protein-free acid-digestion products of proteins, as will be shown 

 later in the paper. 



Opsine as a culture medium 



The opsine was obtained from Paris in small metal capsules. 

 In its original state it resembles highly concentrated commercial 

 meat extract, although much lighter in color. It dissolves readily 



' M. Gr^my, Rue de la Tour d'auvergne, Paris. 



