I9I5] 



C. H. Crabill and H. S. Rced 



37 



or not at all. Perhaps the failure of many of them to grow is not 

 due to their inability to produce proteases but to the fact that the 

 uneven distribution of the fibrin clumps makes it difficult for the 

 organisms to get started. See Table 5 for typical data. 



Protein-agar. A sample of commercial protein prepared from 

 wheat is ground very fine in a mortar and added to the stock agar 

 to the amount of i gm. per 100 c.c. Table 6 presents typical results. 



TABLE 6 



Data pertaining to tests for protease-proditction on protein-agar 



Erepsin, Erepsin hydrolyses the simpler proteins into amino 

 acids, such as leucin and tyrosin. It is best demonstrated by its 

 solvent action upon the simpler proteins. 



Casein-agar. To the stock agar technical casein, in a finely 

 divided condition, is added to the amount of i percent. This me- 

 dium shows in an excellent manner the action of ereptic enzymes. 

 Many of the organisms tested secrete erepsin in such quantity as to 

 dissolve entirely all the casein in a wide band around the colonies, 

 producing thereby a notable halo. A series of plates of casein agar 

 was made in which the agar was rendered neutral to rosolic acid 

 with ammonium hydroxid. All the organisms tested made a much 

 weaker growth and produced much poorer halos on this series 

 than on the slightly acid series. Erepsin is elaborated with greater 

 rapidity and works best in the presence of a slight amount of acid. 



The bacteria were grown only on the alkaline agar because they 



