82 The Opsonic Index — A Medico-Statistical Enqniry 
Distribution of 
Number of 
Leucocy 
I'ES WITH 
Bacteria 
Ingested 
Normal 
Immune 
Serum 
Serum 
0 
20 
41 
I 
26 
52 
2 
36 
57 
3 
45 
42 
4 
42 
30 
39 
24 
(J 
29 
20 
22 
8 
8 
13 
9 
10 
7 
10 
9 
2 
11 
2 
6 
13 
2 
13 
1 
2 
; 
15 
0 
16 
1 
17 
0 
; 
18 
1 
0 
19 
0 
20 
0 
31 
z 
0 
1 
Means 
4 -43 ±-07 
3-33 ±12 
Standard 
3-18 
Deviations 
2-98 
Opsonic Index 0'75. 
In all probability the further dilution of the sera would bring out the real 
differences between them. This was done at the time but the slides have not 
yet been counted. The example serves to show how a strongly opsonic serum 
may yet under certain conditions give an index actually below normal. The reason 
for this paradox was that strong agglutination of the bacteria took place with the 
test serum, whereas no visible agglutination took place with the normal serum. 
The resulting effect was, we may suppose, that for the test serum the agglutination 
so reduced the concentration of the emulsion as to diminish the phagocytosis 
below that which took place for a normal serum and a concentrated emulsion. 
Bacteriolytic action may have contributed to the diminution in the case of the 
immune serum. With both immune and normal sera a considerable amount of 
intracellular digestion had taken place. Now although agglutination is often 
rapid with concentrated emulsions of bacteria, it is much slower for thin emulsions. 
Opsonic action, on the other hand, is still very rapid even with thin emulsions. 
With dilution of the emulsion the agglutinating action would be slower and the 
opsonic action would proceed without this disturbing factor. The same argument 
would in all likelihood apply to a dilution of a strongly agglutinating serum, even 
