CULTUltAL REQUIREMENTS OF BACTERIA 337 



bacteriologists. In the case of the two substances which have 

 been described in the present paper, one may anticipate that 

 they may develop significance for animal metaboUsni as further 

 information on their properties is gained. Whether they are 

 related to the vitamines, and constitute, as Funk (1920) has sug- 

 gested a Vitamine D, connected with deficiencies in certain 

 proteins, is a question which can so far not receive an answer. 

 The writer has preferred to avoid the conception of "vitamine" 

 as far as possible in the experimental approach to the problem. 

 In any case, the method as it has developed, offers a simple 

 biological test for the presence of these compounds, which has the 

 very great advantage that it may be quickly carried out. All 

 the test solutions are easily prepared, and the growth test itself 

 requires only twenty-four or at most forty-eight hours for com- 

 pletion. With this advantage, it should prove possible to iso- 

 late and identify these compounds unless their properties are 

 such that decomposition or molecular rearrangement follows 

 their purification. Work is being carried on with both fractions, 

 and it is hoped to have more data available for report in the 

 near future. 



CONCLUSIONS 



1. Peptone-free beef heart infusion plus glucose and inorganic 

 salts constitutes a satisfactory medium for the hemolytic strep- 

 tococcus. 



2. Short boiling of heart infusion with 2 per cent wood char- 

 coal ("Norit") removes some component of the meat infusion 

 and renders it no longer suitable for the streptococcus. 



3. Such an inactive infusion may be reactivated by the addi- 

 tion of small quantities of peptone or acid hydrolysate of cer- 

 tain proteins, such as casein and edestin. 



4. Acid hydrolysates of such proteins, as wool, silk and wheat 

 gluten are not suitable for reactivation. 



5. The activating material may be precipitated from hydroly- 

 sates of casein by means of HgS04. 



6. It may be separated into two fractions, active only when 

 mixed together, by means of fractional precipitation of the first 



