Dissociation of Microbic Species. 



39 



flocculation whatever was observed at the same Ph in the Na 

 lactate-lactic acid series. It would appear that either the Cl~ of 

 the acid, or the glycocol possessed the property of broadening the 

 optimum zone or of shifting it toward a higher C H +. 



Acid Agglutination of Types G and D in Various Buffer Series. 







Complete Flocculation. 



Buffer Series. 



Ph Range. 



G. 



D. 



Glycocol HC1 



3.0 to 1.2 



3.0, + + at 2.8 



3.0 to 2.4 



Na lactate-lactic acid 



4.7 to 2.4 



4.7 to 4-1 



3-5 to 3-3 1 



Na acetate-acetic acid 



5-6 to 3-2 



4-7 to 3-8 



3-5 to 3-2 



This and other considerations led to experiments which suggest 

 an explanation for the granular growth of microbe G in plain 

 broth. Washed suspensions of this organism are strongly aggluti- 

 nated by beef infusion between P H = 74 and 6.8. This range 

 represents the C H + occurring during the growth of type G in 

 broth. On the other hand, peptone (Fairchild) and Na 2 HPC>4, 

 the other constituents of broth, agglutinate type G very little or 

 not at all in this acidity. 



Types G and D were next subjected to tests with varying 

 amounts of beef infusion, which were adjusted to varying acidities, 

 from P H = 7.5 to P H = 2.0. The dilutions of beef infusion were 

 varied from 1-2 to 1-40. Each dilution was tested over the 

 range of acidity just mentioned. Incubation at 43 0 C. for 16 

 hours. It was found for type G that as the acidity increases, 

 down to P H = 4.5, the amount of beef infusion necessary to 

 cause complete agglutination becomes less. At P H = 4.5 to 

 Ph = 4-0, complete flocculation occurs with traces of beef in- 

 fusion or with none at all. But as the acidity is increased beyond 

 this point, that is, at P H =4.o, increasing amounts of the beef in- 

 fusion are necessary to produce this result. The same phenom- 

 enon is observed for type D, the only difference being that the 

 complete flocculation of this variety by a given concentration of 

 beef infusion demands a higher C H + than in the case of type G. 

 For type D, the optimum zone lies between P H = 4.0 and P H 

 = 3.0. Beyond this, in the direction of greater acidity, more and 

 more beef infusion is necessary to produce complete flocculation. 



1 No flocculation at 2.7 and 2.4. 



