402 MECHANISM OF GRANULAR GROWTH 



optimum shifting from pH 3.5 to 2.5. The results recorded in Tables 

 IV and V are graphically represented in Fig. 3. 



It is interesting to observe that for Microbe D strong concentrations 

 of peptone (0.5 and 0.25 cc. of 1 per cent solution) actually suppress 

 flocculation completely at pH 3,0. The effect of peptone, contrary 

 to that of beef infusion, would appear to be a stabilizing one. 



SUMMARY. 



The acid agglutination optimum of Microbes D and G is not inde- 

 pendent 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. 



BIBLIOGRAPHY. 



1. Beniasch, M., Z. Immunitalsforsch., 1911-12, xii, 268. 



2. Unpublished experiments in collaboration with J. H. Northrop. 



3. Michaelis, L., Deutsch. med. Woch., 1911, xxxvii, 969. 



4. Sorensen, S. P. L., CompL rend. Trav. Lab. Carlsberg, 1909, viii, 1; Biochem. 



Z., 1909, xxi, 131, 201. 



5. DeKruif, P. H., /. Gen. Physiol., 1921-22, iv, 387. 



