Observations on Bacterial Metabolism. 15 



strains of the pneumococcus. While it has thus far not been 

 possible to isolate the compound in pure form, perhaps enough 

 has been learned of its occurrence and properties to warrant a 

 short note. 



If an infusion of beef, or better, of beef heart muscle be pre- 

 pared by boiling a pound of the chopped muscle in a liter of water, 

 straining and filtering, and if 0.1 per cent, glucose and a nitrogen 

 free inorganic salt mixture be added, it is found that the broth 

 thus prepared is quite suitable for growth of the hemolytic strep- 

 tococci. A P H of 7.2-7.6 is most favorable, and no peptone or 

 other nitrogenous material need be added. If, however, the meat 

 infusion be mixed with 2 per cent, of wood charcoal, of the com- 

 mercial brand called "Norit," and boiled for fifteen minutes and 

 filtered, the streptococcus will no longer grow on the filtrate, 

 after adding glucose, and salts, and adjusting the reaction. Evi- 

 dently a substance has been quantitatively removed from the 

 infusion by the charcoal which is required by the streptococcus 

 for growth. The addition of 1 per cent, commercial peptone to 

 such a charcoal treated infusion now renders it again suitable for 

 growth, although the peptone itself, plus glucose and salts, will 

 not give growth with the streptococcus. 



Since the material which is removed by the charcoal is appar- 

 ently present in commercial peptone, it seemed most probable 

 that an amino-acid or polypeptide was in question. The addition 

 of a sulphuric acid hydrolysate of casein to the charcoal treated 

 infusion was next tried, and found to be quite as effective as the 

 peptone. The hydrolysate is prepared by 18 hrs. boiling with 

 33 per cent. H 2 S0 4 , and the acid then removed with baryta. 

 To rule out as far as possible the presence of non-protein impurities 

 in the casein, a purified specimen was prepared by reprecipitating 

 three times with acetic acid from Na 2 C0 3 solution, and finally 

 washing thoroughly with alcohol and ether. An acid hydrolysate 

 of this casein proved equally active when added to the inactive 

 infusion. Similarly, active preparations could be obtained by the 

 use of a sulphuric hydrolysate of edestin and meat residue, and 

 very weakly active preparations from egg white, but the hydroly- 

 sates of wheat gluten, gelatine, wool and silk were quite inactive. 

 Published analyses of these proteins did not show any amino 



