388 



INFLUENCE OF THE DILUTION OF SERUM, 



to unity; and, in the case of the thickest suspension in which 16 

 cells were englobed in the undiluted serum-test, there is a break 

 at the one-quarter dilution. In this respect the curve is identical 

 with that found by Dean. It may be said, however, that this 

 was the only time that the typical Dean-curve was obtained; 

 and, from a consideration of the later results in which dilutions 

 between undiluted serum and a two-fold serum were tested, it 

 appears probable that there should be no sharp break in the curve. 



The quarter and eighth dilutions, however, appear to be points 

 about which the curves deviate from regularity. As will be seen 

 later, there is frequently obtained a more or less pronounced 

 "hump" iu the curve about these dilutions. In this experiment 

 these " humps " may have occurred at the ^ dilution with the 

 thick suspension, at the ^ with the medium, and slightly at the 

 Jg- with the thinnest suspension. 



Speaking generally, the number of bacteria ingested is assumed 

 to be a measure of the amount of opsonin in the serum. This is 

 true up to a certain point and under certain conditions, but 

 beyond this the opsonic influence is afiected by the conditions 

 which influence phagocytosis. The saline content is such a con- 

 dition. There may be either too little or too much salt in the 

 serum to bring about a maximum phagocytosis under the condi- 

 tions of the experiment. 



The p. feet of adding salt to the serum. — In the following experi- 

 ment the serum was treated with finely powdered sodium chloride 

 in quantity to make a 085% solution; and this was progressively 

 diluted with 0-85^ normal saline. 



