BACTERIAL AUTOLYSIS 555 



absolute and the relative amounts of the various forms of nitro- 

 gen. The present investigation is essentially an attempt to 

 follow these changes by simple and practical chemical and 

 physico-chemical methods. 



METHODS AND EXPERIMENTAL PROCEDURE 



The quantitative biuret test as employed by Vernon (1903) 

 was found to be a valuable method of determining the relative 

 amounts of protein and other closely related nitrogenous sub- 

 stances. Increases in amino and ammonia nitrogen were 

 followed by the Sorensen titrations (1908). Amino nitrogen 

 was determined also by the Van Slyke method (1911 and 1912). 

 Observations were also made of the changes in conductivity of 

 the autolyzing suspensions of bacteria, a procedure used by 

 Sjoquist (1895) and later by Bayliss (1904) in their studies 

 of digestion. 



The organisms which were selected for the investigation may 

 be placed in three distinct classes. The first is made up of those 

 which are powerfully proteolytic, B. subtilis, Erythrohacillus 

 prodigiosus, and related species. These are all gelatin-Uquefiers. 

 The second class is non-proteolytic and includes the colon- 

 typhoid group. The third includes certain of the pathogenic 

 cocci which possess little or no proteolytic power, namely Stct^ 

 phylococcus aureus, Streptococcus pyogenes, the pneumococcus, 

 gonococcus and meningococcus. 



The non-pathogenic organisms were grown on plain two per 

 cent agar. Some of the pathogenic cocci required special media. 

 A luxuriant growth of the pneumococcus, gonococcus and men- 

 ingococcus was obtained by the addition of one part of ascitic 

 fluid to two parts of three per cent agar. An even more satis- 

 factory medium was the testicular extract agar which Hall 

 (1916) recommends for the cultivation of the gonococcus. This 

 medium has the advantage of not being affected by ordinary 

 sterilization methods. The meningococcus was grown on liver 

 extract agar in the experiments which involve amino nitrogen 

 determinations. In one instance the pneumococcus was grown 

 in fresh extract broth and the organisms removed by centrifuging. 



