BY R. GREIG-SMITH. 



561 



The amended phagocytic index is identical with that of the 

 unheated dilute serum, and that is what we should expect to find. 



Opsonisation with diluted sekum. 



Opsonisation with the same serum undiluted. 



Heated at 60*^ + suspension + corpuscles 

 Not heated + suspension + corpuscles . . 



Phagocytic Index, (25) =0 

 Phagocytic Index, (20)-=25 



The clumping that occurred in certain of these tests was pro- 

 nounced, and strongly supports the idea that opsonisation is a 

 phase of agglutination. We must distinguish between a deposi- 

 tion of a precipitate and the flocculation of the same. The pre- 

 cipitate formed by the action of the agglutinin (precipitin or 

 opsonin) upon the agglutinable substance oozing through the 

 bacterial membranes is deposited upon the capsules of the cells 

 This is probably opsonisation, and is the first phase of the com- 

 plete phenomenon. The second is the flocculation of these 

 ■deposited films, that is the agglutination of the opsonised bacteria 

 under the further influence of the saline matter of the suspension. 

 In the first test there was opsonisation without agglutination, 

 because a sufficient time had not been given for the second phase 

 to develop. In the second, third and sixth tests, even when the 

 •dilute serum had been heated, the time was sufficient for the 

 phenomenon to be complete. 



An alkaline citrate was used in diluting the serum for the 

 purpose of hindering the clumping and thus regulating the 



