HYDROGEN ION CONCENTRATION AND PROTEOLYSIS. 175 



Deteeimination of the Endo- or Exo-enzymatic Nature of Enzymes. 



Does B. subtilis produce endo- or exo-enzyme? To determine this the 

 following procedure was adopted: after B. subtilis was cultivated in 

 500 cubic centimeters of Medium IV. (Ph = 6.90), at 37° C. for 120 hours, 

 the contents were divided into two equal portions; namely, A and B. 

 Portion A was filtered through a Chamberland porcelain filter^ under 

 aseptic conditions, and the filtrate, together with portion B (in the original 

 condition), was placed in the incubator at 37° C. for forty-eight hours. 

 At the end of this period the filtrate was carefully examined both macro- 

 scopically and microscopically, in order to verify sterility. The filtrate 

 was then taken for inoculation. Three flasks were filled with 400 cubic 

 centimeters Medium IV. (Ph = 6.90). One of these was kept for control 

 and marked "control;" the second one was marked "1," and inoculated 

 with 1 cubic centimeter of the portion B; and the third was marked "2" 

 and inoculated with 1 cubic centimeter of the filtrate A. These flasks 

 were kept in the incubator and the determinations for Ph and formol 

 titrating nitrogen were made. The results are indicated on Table XII. 

 and represented in Graph 3. 



Table XII. — Determination of Character of Enzyme. 



F. N. — formol titrating nitrogen. 



' Zak. Hofm. Beitr., 10, 287, 1907; Schmailowitsch, F. Zbl. Biochem., I, 467; de Waele, H. 

 Zbl. Bakt., 50, 40, 1909. 



2 Milligrams in 100 cubic centimeter medium. 



