jan. 2, i 9 i7 Diagnosis of Tuberculosis by Complement Fixation 17 
instances a retrogressive tendency. Such moderate lesions might not 
induce the formation of sufficient antibodies in the animal to permit detec¬ 
tion by the test. 
TESTS OF HUMAN SERUMS 
A limited number of human serums were also included in the tests in 
order to establish whether the results with a certain antigen would be 
more reliable with animal serum than with human serum. In all, 22 
cases were tested. Most of the positive serums were obtained from 
patients of the Tuberculosis Hospital at Washington, D. C., through th* 
courtesy of the authorities. These tests are summarized in Table X. 
Table X .—Summary of the tests on human serums conducted with an antigen prepared 
from a bacillary emulsion and tuberculin precipitate 
Human serum. 
Number 
Degree of fixation. 
Percent¬ 
of cases. 
+++ + 
++4- 
++ 
+ 
± 
- 
age. 
1. Apparently healthy.... 
5 
e 1 
2. Clinical symptoms present, sputum 
negative. 
4 
I • 
d 
x 
33 
67 
100 
3. Clinical symptoms moderate, spu¬ 
tum positive. 
3 
2 
1 
4. Clinical symptoms progressive, spu¬ 
tum positive. 
6 
x 
I 
I 
5. Clinical symptoms severe (cavities), 
sputum positive. 
4 
x 
I 
5 ° 
Total. 
22 
c 
70 
j 
7 
From Table X it appears evident that the results are not more reliable 
than in bovine tuberculosis and also that the degree of the reaction has 
no bearing on the extent of the disease. However, it is recognized that 
the number of human cases tested does not warrant any definite conclu¬ 
sions. 
CONCLUSIONS' 
(1) The complement-fixation test for the diagnosis of tuberculosis in 
cattle is not so reliable as the subcutaneous tuberculin test. 
(2) Since a large proportion of the positive cases give only a faint reac¬ 
tion, it necessitates a very careful titration of the antigen and a most 
accurate observance of all of the details of the technique of the test. 
(3) The amount of fixation can not be considered as an index to the 
extent of infection. Frequently samples from animals showing arrested, 
retrogressive lesions gave a more marked fixation than animals affected 
with acute, progressive, generalized tuberculosis. 
(4) The complement-fixation test might be employed as a supplemen¬ 
tary test in cases of doubtful or atypical reactions to the subcutaneous or 
other allergic tests. It is not practical for general diagnostic purposes. 
(5) The subcutaneous tuberculinization of healthy animals affects the 
results of the complement-fixation test. Such interference may be 
noted as early as on the fourth day following the injection and may per¬ 
sist for at least six weeks, and possibly for a much longer time. 
