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CONTENTS. 



Bulletin 167. I. The relation of hydrogen ion concentration of media to the 

 proteolytic activity of Bacillus subtilis. II. Proteolysis of 

 Strept. erysipelatis and Strept. lacticus compared under different 

 hydrogen ion concentration, ....... 139 



Part I. 

 Introduction, ......... 



Review of previous investigations, ..... 



Questions involved, ........ 



General methods of procedure, ...... 



Choice of methods, ....... 



Determination of the hydrogen ion concentration in culture media 

 ("true reaction"), ...... 



Determination of proteolysis, ..... 



Theoretical discussion of formol titration, . 

 Preparation of media, ....... 



Steps in selection of medium, ..... 



Preparation of media of different hydrogen ion concentration. 

 The colorimetric method, ..... 



Acclimatization of the culture, , , . . . , 



Inoculation of the culture media, ..... 



Results, .......... 



Testing the vitality of the organism (B. subtilis). 

 Determination of the rate of growth, .... 



Determination of the rate of proteolysis, 



Determination of hydrogen ion concentration as growth progressed. 



Determination of character of the proteolysis, .... 



Determination of the endo- or exo-enzymatic nature of enzymes. 



139 

 141 

 143 

 145 

 145 



145 

 152 

 152 

 155 

 155 

 161 

 161 

 166 

 167 

 167 

 167 

 1C8 

 169 

 172 

 174 

 175 



Part II. 

 Introduction, ...... 



General methods of procedure, . 



Organisms employed in the investigation. 

 Streptococcus erysipelatis, . 

 Streptococcus lacticus, 

 Medium, ...... 



Rate of growth. 

 Rate of proteolysis, . . 



D^etermination of hydrogen ion concentration as growth progressed, 

 Summary and conclusions. 



Part I 



Part II 



178 

 178 

 178 

 178 

 178 

 178 

 ISO 

 181 

 183 

 184 

 184 

 184 



