W. F. Harvf.y and a. M'^Kendwck 
81 
to have a graded series of frequency distributions showing the transition from the 
inhibitory action of toxins to the maximum development of phagocytosis. Again, 
it would be interesting to observe the gradual shrinking of the range of phago- 
cytosis with thinning of the emulsion. We may learn from this example that 
there is probably an optimum concentration for the production of maximum 
phagocytosis. Doubtless the same phenomenon would be shown by immune sera 
and by some other organisms than the one here tested. The question immediately 
arises as to whether this transition would take place at the same point for both an 
immune and a normal serum. If it did not, we should certainly not get indices 
which were the same for different degrees of concentration of emulsion, although 
the normal and immune sera were the same throughout. 
Number of 
Bacteria 
Ingested 
Original 
Emulsion 
Dis 
5 fold 
dilution 
TRIBUTION 
10 fold 
dilution 
OP Leoco 
20 fold 
dilution 
CYTES WIT 
40 fold 
dilution 
a 
80 fold 
dilution 
100 fold 
dilution 
0 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
n 
15 
16 
17 
18 
19 
20 
317 
345 
172 
82 
47 
20 
11 
4 
1 
0 
1 
40 
92 
112 
142 
121 
99 
100 
86 
64 
45 
41 
17 
11 
9 
2 
2 
3 
2 
2 
5-03 
3-38 
43 
101 
137 
139 
130 
115 
111 
74 
55 
32 
24 
12 
9 
6 
1 
1 
0 
1 
112 
180 
184 
151 
128 
96 
63 
44 
22 
10 
4 
3 
3 
192 
278 
221 
139 
91 
49 
21 
4 
4 
1 
632 
282 
65 
16 
4 
1 
620 
282 
79 
16 
2 
1 
Means 
Standard 
Deviations 
1-34 
1-41 
4-54 
2-98 
3-05 
2-29 
1-94 
1-62 
0-48 
0-74 
0-50 
0-74 
Example 2. The effect of extracellular agglutination of the bacteria of the 
emulsion by the test serum. The organism used was the Bacillus Friedlander 
and the emulsion was again a concentrated one. The index given by the test 
serum as determined in the ordinary routine work of the laboratory with a thin 
emulsion was 2'17. What a contrast to this is presented by the index obtained 
with a very thick emulsion — viz. 0'75 ! The determination, it is true, was made 
on the following day, but age of serum will not account for this amount of lowering 
of the index. 
