398 



INFLUENCE OF THE DILUTION OF SERUM, 



It is seen, from the last experiments, that the curve always 

 rises from unity to the half-dilution. The dilution-curve, as 



Fig. 8. — Thick and thin suspensions of bacteria with different salines. 



represented by Dean, would therefore appear to be misleading; 

 and a curve of a different order would have been obtained, had 

 he examined dilutions between normal and half-strength. 



The curve becomes almost a straight line when the saline con- 

 tains from 1-0 to 1-1 % of sodium chloride, and when certain 

 thicknesses of bacterial suspension are employed. What these 

 are, can be determined only by experiment, for there appear to be 

 slight daily variations which prevent any definite information 

 being given. 



Conclusions arrived at from the experiments. — The investigation 

 has shown that several factors have each an influence in modify- 

 ing the nature of the curve representing the opsonic and phago- 

 cytic effects obtained upon progressively diluting normal serum. 

 The most important of these is the strength of the saline employed. 

 It would be possible to obtain the phagocjnic indices so that 

 their ratios lay upon a straight line, by using a solution of sodium 



