The acid agglutination optimum of Microbes D and G is not independent of the nature of the buffer mixture. Glycocoll-HCl buffer mixtures cause complete flocculation at high CH+ (2.7 to 2.4), at which points little or no flocculation occurs with the Na lactate-lactic acid buffer series.
Beef infusion has the property of broadening the acid agglutination optimum of both Microbes D and G, bacilli of rabbit septicemia. This extension is in the direction of a lower CH+.
There is no evidence that the beef infusion has the power, per se, of agglutinating these organisms. It would seem merely to increase their sensitiveness to sedimentation in the presence of H ions.
The data presented explain the mechanism of the granular growth character of Microbe G in liquid media as compared to the diffuse growth of Microbe D.
Peptone (Fairchild), contrary to beef infusion, shifts the acid agglutination optimum of Microbes D and G in the direction of a higher CH+. Strong concentrations of peptone exhibit an inhibitory effect on the agglutination of Microbe D in the optimum zone.
