CALVIN B. COULTER 



777 



in which it was not included. It depends apparently upon the greater 

 preservation of the end -piece function at this reaction. This will 

 be referred to later. If the heated complement be added, without 

 separation into its fractions, to sensitized cells together with unheated 

 mid- and end-piece in separate series, the upper curves of Fig. 4 

 result. The two maxima observed at pH 6.9 and at pH 6.1 to 6.4 

 appear to be an expression of the quantitative relations between 

 the two fractions, according to which the degree of hemolysis is in- 



70 



60 

 ^. 50 

 g 40 



20 

 10 







pH 7.4 7.2 7.0 6.8 6.6 6.4 6.2 6.0 5.8 5.Q 5.4 5.2 



Fig. 4. The complementary activity of whole serum heated to 40°C. in distilled 

 water dilution, by itself and in the presence of added mid- and end-piece. The 

 curve marked end-piece is that given after the addition of the titer amount of 

 mid-piece to each tube; that marked mid-piece is that given after the addition 

 of the titer amount of end-piece to each tube. 



creased if the amount of either mid- or end-piece is increased up to 

 the titer value of each.^ 



The activity retained by the isolated end-piece fraction, freed 

 from mid-piece by the precipitation of the euglobulin and heated 

 in dilution in distilled water is shown in Fig. 5. In the experiments 

 recorded here with the isolated fractions the original activity of 

 the complement was completely restored on reuniting the unheated 

 fractions, and the curves that show the effect of heating are essen- 

 tially the same whether the activity is estimated from the base-line 



