186 
PRINCIPLES OF BACTERIOLOGY 
blood cells (the antigen), a guinea pig’s serum (the 
complement) and the rabbit’s serum (the amboceptor), 
and these three substances unite, in this case, there is 
a change visible to the naked eye, namely, the turbid 
contents of the tube become clear and the red blood cells 
of the sheep, disappear—this is called hemolysis, and is 
due to the rabbit’s serum having produced the ambocep¬ 
tor against the sheep’s red blood cells. 
Now, in the Wassermann test, we put into a test tube 
the syphilitic antigen (a preparation from spirocheta 
pallida), the complement (a guinea pig’s serum) and the 
patient’s blood serum which may or may not contain 
the syphilitic serum depending on whether or not the 
patient has syphilis. We incubate this at 37° C. for 
thirty minutes to permit the three substances to unite. 
Then add to the tube the rabbit’s serum and the 
sheep’s red blood cells, and again incubate for thirty 
minutes, at the end of which we take out the tube and 
examine it. If the patient has syphilis, his blood serum 
must have the syphilitic amboceptor, so that at the first 
incubation, this amboceptor and the syphilitic antigen 
must have united together, so that when we added the 
rabbit’s serum and the sheep’s red blood cells all com¬ 
plement had been bound up by the syphilitic system 
(the antigen and the amboceptor) and none was avail¬ 
able for the hemolytic system (the rabbit’s serum and 
the sheep’s red blood cells) and consequently these 
two could not unite with the complement and the con¬ 
tents of the tube did not become clear, that is, hemolysis 
did not take place; if on the other hand, the patient 
did not have syphilis, and his serum did not have the 
syphilitic amboceptor, then, after the first incubation, 
the complement was free, and, upon the addition of the 
hemolytic system (the rabbit’s serum and the sheep’s 
