1907.] Properties of the Opsonin of an Immune Serum. 193 



Immune Serum. 



Anti-staphylococcus serum (heated at 55° C.) 7*8 



„ „ treated with Staphylococcus aureus 0*36 



„ „ „ Bacillus coli 8'8 



„ „ „ V. Metchnikovi 7'5 



„ „ „ Bacillus tuberculosis 7'9 



„ „ „ Bacillus pyocyaneus 6'7 



The tables show that emulsions of all the organisms tested produce a 

 marked diminution of the normal opsonin, whereas none of them, with the 

 exception of the staphylococcus, have any appreciable effect on the immune 

 opsonin. 



In another experiment we treated the heated immune serum twice with large 

 quantities of B. coli, B. dysenteries, Cholera spirillum, B. typhosus, Staphylococcus 

 pyogenes albus. In the case of the last mentioned, there was apparently a 

 slight diminution of the opsonic power, viz., from 26*7 to 20*3 — a compara- 

 tively trifling effect in view of the close relationships of the two organisms ; 

 the serum was, however, practically without opsonic effect on the Staphylo- 

 coccus albus. In the case of the other bacteria mentioned, there was no 

 diminution whatever of the opsonin after treatment with the organisms. 



These experiments, by the method of absorption, bring out a very marked 

 difference as regards specificity between the opsonins of a normal and of an 

 immune serum. With the exception of the possible slight effect in the case 

 of the Staphylococcus albus, we have failed to find any organism, except the 

 Staphyloccocus aureus, which absorbs the opsonin from the heated anti- 

 staphylococcus serum. In the case of the opsonins of a normal unheated 

 serum, the result is entirely different, as is shown by the table given above. 

 Every organism tested has absorbed large quantities of opsonin when the 

 Staphylococcus aureus is used as the test for opsonic action.* At the same 

 time, the staphylococcus appears to remove this opsonin more quickly than 

 any of the others. We have tested to what extent it is possible to remove 

 the opsonin of normal serum for Staphylococcus aureus by treating the serum 

 twice with an emulsion of another organism, e.g., the B. coli. The results 



are : — 



Normal Serum. 



Opsonic index. 



Guinea-pig's serum (unheated) 2T5 



„ „ treated once with Staphylococcus aureus 1*0 



» » » twice „ „ 0-4 



„ „ ,. once with B. coli i 2*1 



» » » twice „ 1-3 



* These results, so far as the normal opsonins are concerned, are in harmony with those 

 of Simon Lamar and Bispham, whose paper (' Journ. of Exper. Med.,' December, 1906 

 p. 651) has come into our hands since the present communication was written. 



