CULTURAL REQCriREMENTS OF BACTERIA 



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soaked in cold water in the proportion of 1 pound of meat to 500 

 cc. of water, and heated to 55° for a few moments and strained. 

 The residue was boiled for five minutes with a second 500 cc. of 

 water, and strained, and the extraction repeated a third time. 

 The first extract was boiled to remove coagulable material, and 

 all three extracts were filtered. Media were prepared in the 

 following way, and after inoculation, gave the results indicated: 



Other experiments of the same kind have given hke results, 

 but there is enough irregularity so that the method is not ideal. 

 It does, however, bring further evidence as to the presence of 

 two classes of compounds in the meat infusion. Further work 

 with the method, substituting known amino acids instead of 

 peptone, may lead to more positive results. 



2. Chemical fractionation of meat infusion. From the fact 

 that commercial meat extract cannot replace meat infusion for 

 the growth of the pneumococcus and streptococcus, one may 

 suppose that heating, oxidation or simply long preservation may 

 destroy the active material. If it can be shown experimentally 

 that these or other comparatively simple chemical processes 

 are destructive, plans for chemical separation can then be made 

 in such a way as to avoid or minimize this difficulty. Accord- 

 ingly, a few simple tests were made on the influence of such 

 ob\dous procedures as suggested themselves. It was found that 

 drying on the water bath, long boiling (two to three hours) in 

 neutral or moderately acid solution (2.5 per cent HCl) and 



