PHYSICO-CHEMICAL PROPERTIES 87 



Instead of titrating tlie skin-preparatory potency, however, 

 more accinate titrations ol reacting potency \vere done. The mean 

 titers were derived in the same manner as in the work on dialysis 

 (p. 73) . By accurately titrating the reacting factors of the phe- 

 nomenon, it was fotmd that, in agreement with Apitz: (1) the 

 alkaline insoluble N fractions were always inactive; (2) the nti- 

 cleoprotein P fractions were practically always active; (3) the 

 supernatant alcoholic sohitions, after concentration in vacuo, were 

 inactive; and (4) the alcohol precipitated C fractions ^\ ere highly 

 potent but frequently labile, in one instance being completely in- 

 activated dining preparation. The isolation of a biinet-negative C 

 fraction, however, has not been confirmed. 



Since cjualitative color tests as indications of chemical structine 

 must be accepted with considerable reserve, attention is called 

 to the following analytical data; the high nitrogen values con- 

 sistently foimd in the various C fractions, {i.e., 8.1, 8.5 and 12.4 

 per cent) suggested the presence of appreciable quantity of pro- 

 tein-like substances. Accordingly, when fraction C of one batch 

 was refluxed for two and one-half hours in 2 N HCl, only 10.4 

 per cent reducing sul)stances, calculated as glucose, were formed. 

 For comparison, it may be noted that on hydrolysis, the specific 

 carbohydrates of Types II and III pneimiococcus, -which do 

 not contain any nitrogen, yield aboiu 70-75 per cent reducing 

 substances calculated as glucose; whereas that of Type I pneu- 

 mococcus, containing 5.8 per cent nitrogen, is hydrolyzed to the 

 extent of 28 per cent (Heidelberger, 1927) . It must be empha- 

 sized, therefore, that in its present state of purity, fraction C can- 

 not be designated as a carbohydrate. By titrating the reco\'ery of 

 reacting factors, it has been fotmd that most of the activity origi- 

 nally present in a bacterial filtrate ^sas lost ^vith the foregoing 

 procedines of concentration. E\en ^vith the best recoveries ob- 

 served, the extent of pinification attained was insignificant when 

 the activity per milligram of dry -\\eight or of nitrogen ^vas 

 measined. 



RECAPITULATION 



The acti\e principles of the phenomenon possess considerable 

 heat resistance which may differ some\vhat ^vith various micro- 

 organisms and even with strains of the same microorganisms. It 

 inay also be influenced bv tlie mode of preparation of the ma- 

 terial. 



