398 



MECHANISM OF GRANULAR GROWTH 



Of these three solutions, at pH 7.4, beef infusion alone showed 

 marked flocculating activity against Microbe G. 



The flocculating effect of beef infusion at varying acidities was now 

 tested. The beef infusion solution just described was titrated with 

 n/10 HCl to increasing degrees of acidity, from pH 7.5 to pH 2.0. 

 The beef infusion at all of these Ch+ was now diluted with distilled 

 H2O, the dilutions increasing from 1:2 to 1:40. Each of these dilu- 

 tions at each pH, was now added in equal volume to 1 cc. of distilled 

 water suspensions of four times washed Microbes D and G. The 

 mixtures were kept in the water bath for 16 hours at 43°C., and read- 

 ings taken. The results are recorded in Tables II and III. 



TABLE II. 



Beef Infusion Agglutination of Microbe G at Varying Ch+. 



Table II shows for Type G, that, as the acidity increases down to 

 to pH 4.5, the amount of beef infusion necessary to cause complete 

 agglutination becomes less and less. At pH 4.5 to pH 4.0 traces of 

 beef infusion cause complete agglutination. This point corresponds 

 to the acid agglutination optimum of Microbe G in various buffer 

 series. Beyond this point, that is, at pH<4.0, increasing amounts of 

 beef infusion are again necessary to produce complete flocculation. 



Table III shows the same effect in the case of Microbe D, the only 

 difference being that complete flocculation of the D type by a given 



