THE COMPLEMENT FIXATION TEST FOR SYPHILIS: 
INCUBATION FOR FIXATION AT ICE-BOX TEMPER- 
ATURES 
By First Lieut. Joseph W. Smith, Jr. 
Medical Corps, United States Army 
To designate the Wassermann reaction as a complement- 
fixation phenomenon is not strictly in accord with our knowledge 
of the test. The reaction was at first regarded as an immunity 
test depending upon a reaction between antibodies specific for 
Spirochseta pallida on the one hand, and the specific protein 
constituents of this pathogenic organism on the other. Looked 
at in this way, a positive test would indicate the existence of 
specific syphilis antibodies in the serum of a patient. This con- 
ception was perforce abandoned several years ago. It has been 
amply demonstrated that extracts of cultures of Spirochaxta pal- 
lida as well as extractions from the testes of syphilitic rabbits 
do not furnish an antigen suitable for the Wassermann reaction. 
At present it is quite generally believed that the test is not a 
specific complement-fixation in the sense of Bordet and Gengou, 
but that it is a somewhat analogous reaction, dependent upon 
the presence, in the serum of syphilitic patients, of substances 
produced indirectly because of the presence of syphilitic infec- 
tion. It may be a relative increase of globulins, or a change in 
the physical state of the globulins or of other substances present 
in the serum. 
None of the theories of the Wassermann reaction has been def- 
initely proven; all are still only theories, or probably really no 
more than hypotheses. However, despite the lack of logical, 
theoretical considerations in relation to the test, and although 
much that has been said and written and done regarding it has 
been erroneous, the Wassermann reaction has a soul of truth 
and has persistently survived all manner of abuse and mutila- 
tion. It finds its justification in its practical value, attested by 
experience. As a necessary corollary it results that a proposed 
antigen or a proposed technic finds favor not according to its 
theoretical specificity but only through extensive and satisfac- 
tory use upon a large series of patients. Although clinical satis- 
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