FIXATION OF COMPLE^IENT 111 



with a capillary pipette, inactivated by heating for 

 half an hour at 56° C, and stored for future use in 

 1 c.c. glass ampoules. Amboceptor, when collected in 

 this way under aseptic conditions, will retain its ha^mo- 

 lytic power for several months. We have found that 

 the serum is less likely to deteriorate or become con- 

 taminated when mixed with an equal quantity of 

 glycerin, as suggested by Much. The glycerin in no 

 way interferes with the Wassermann test. We also 

 prefer to store the glycerinized serum in short lengths 

 of glass tubing with sealed ends, as suggested to us by 

 Laird, because a larger amount of air must be en- 

 closed in the ampoules, with consequent greater risk of 

 contamination. In the Wassermann test itself we em- 

 ploy 1 c.c. of a 1-1000 dilution of hemolytic ambo- 

 ceptor that gives a titre of at least 1-2000. We avoid 

 having to open a fresh tube of amboceptor and thus 

 wasting a great deal, by making a 1-100 dilution from 

 one tube, placing it in sl sterile flask, and making the 

 1-1000 dilution from this for several days. 



Syphilitic System 



Antigen. — For reasons given above, we prefer to 

 use as antigen an alcoholic extract made from the 

 liver of a syphilitic foetus that has been found on micro- 

 scopic examination to be rich in treponemata. The 

 method usually employed in preparing such an anti- 



