i 7 ,i Smith: Complement Fixation for Syphilis 33 
In a second paper 2 Doctor MacNeal and I presented the re- 
sults of Wassermann tests performed in the laboratories of the 
New York Post-Graduate Medical School and Hospital by six 
methods, on 501 identical specimens from 457 patients. In the 
first of these six methods a cholesterin-reenforced. antigen ‘was 
employed, and the first incubation was carried out at 37° C. In 
the second method a simple alcoholic extract was used as an- 
tigen, with incubation also at 37° C. In the third method an 
antigen prepared from the acetone-insoluble fraction of beef 
heart after the method of Noguchi was used, with incubation 
also at 37° C. Exact duplicates of these tests were prepared 
and incubated at 8° C. for four hours. Tests 4, 5, and 6 differed 
from tests 1, 2, and 3, respectively, only in the temperature and 
the length of time for the first incubation. 
Each antigen was titrated for hemolytic effect, for anticomple- 
mentary action, and for specific antigenic property. The titra- 
tions were made for each set of incubation conditions, that is 
37° C. for one hour and 8° C. for four hours. 
The hemolytic system used was the sheep-rabbit system. Two 
units each of ambo and complement were used in the tests. 
This system is quite sufficiently loose to obviate very largely the 
danger of nonspecific fixation. And yet, as will subsequently ap- 
pear, we found reactions in 16 of the 501 tests (3 per cent), 
which we feel inclined to regard as false positive reactions. 
The sera and spinal fluids were always heated at 56° C. for 
thirty minutes just prior to being tested. 
The cases presented were divided into two classes, on the basis 
of history. The known syphilitics made up the first class. In 
this group were recorded 92 reactions in 80 cases. At 37° C. 
antigens B.H.C. (cholesterinized extract of beef heart), B.H.P. 
(simple alcoholic extract of beef heart), and B.H.A. (acetone- 
insoluble extract of beef heart) yielded, respectively, 52, 26, and 
31 per cent of positive reactions, while by the ice-box method, 
on the other hand, they gave in the same order 76, 64, and 48 
per cent of positive tests. 
The second class of cases was composed of those in which 
there were no histories of syphilis. On the basis of the physical 
findings it was possible to form several subdivisions of this 
group, the first of which consisted of those cases which presented 
lesions typically luetic. In 27 reactions in 24 patients in this 
group the results were as follows : At 37° C., cholesterinized ex- 
tract of beef heart, simple alcoholic extract of beef heart, and 
s Journ. Inf. Dis. 21 3 (1917). 
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