54 
Journal of Agricultural Research 
Vol. VIII, No. 2 
been employing 12 tubes to a test, commencing with 0.2 c. c. of serum 
in the first tube and graduating the amount down to 0.005 c. c. in the 
last tube. 
In the titration of the antigen and in all standardization tests the 
results are read at exactly one hour after the addition of the ambocep¬ 
tor and sheep cells, during which time the tubes were kept in the incu¬ 
bator at a temperature of 37.50° C. 
Table VI illustrates some of the results obtained, the letters beneath 
the varying quantities of serum signifying, N, no fixation of complement; 
S, slight fixation;’Gd, good fixation; and Pf, perfect fixation. 
Table VI .—Results of complement fixation tests with anthrax serum 
Sample. 
Degree of fixation. 
Serum in tubes a . c. c,. 
0.2 
0.1 
0.09 
0.08 
0.07 
0.06 
0.05 
0.04 
0.03 
0.02 
0. or 
0.005 
A&. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
B c . 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N 
C<*. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Gd. 
s. 
N. 
N. 
N. 
n! 
D *.. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Gd. 
s. 
N. 
N. 
E/. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
Fff. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Gd. 
S. 
GA . 
Pf. 
Pf. 
Pf. 
Pf. 
Gd. 
Gd. 
S . 
N. 
N. 
N. 
N. 
N. 
4 » ? . 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Pf. 
Gd. 
N. 
N. 
967. 
Pf. 
Pf. 
Pf. 
Pf. 
Gd. 
vS. 
N, 
N. 
N. 
N. 
N. 
N. 
Normal serum * . 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
N. 
a Where the smaller quantities were used, the serum was first diluted to a known strength to avoid inac¬ 
curacies likely to occur where minute amounts are employed. 
b Sample A. Serum from horse which had been vaccinated and subsequently infected with a minute 
amount of anthrax culture. 
c Sample B. Same as A. 
<* Sample C. Serum from horse undergoing hyperimmunization. Had received growth from 18 agar 
slants five-eighths inch surface 17 days previous to the taking of this sample. 
e Sample D. Serum from horse completely hyperimmunized. 
/ Sample E. Serum from horse which had merely been vaccinated against anthrax. 
Q Sample F. Serum from horse completely hyperimmunized. 
& Sample G. Serum from hyperimmune horse which had been producing serum for over a year. 
* Sample 48. Bureau of Animal Industry hyperimmune horse. Serum known to be of good potency 
through numerous field and laboratory tests. 
t Sample 96. Bureau of Animal Industry hyperimmune horse. Serum known to be inferior to that from 
horse 48. 
* Normal serum. Control. 
The above serums were also employed in animal-inoculation tests, in 
which the results in general corresponded with the complement-fixation 
test. 
While no definite conclusions can be drawn at this time, it appears from 
the results thus far obtained that as the process of hyperimmunization 
against anthrax progresses the complement-fixing action of the serum 
increases. Serum from different animals hyperimmunized by the Bureau 
of Animal Industry proved to be of different potency, one being of a high 
potency and the other of a comparatively low potency. (See Table VI.) 
On applying the complement-fixation test to these samples the comple¬ 
ment-fixing value of the serum of highest potency was considerably higher 
than that of the other serum. Similar results have been obtained with 
serum from outside sources. A number of other samples of serum from 
horses in different stages of the hyperimmunization process were tested, 
