432 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



The following table illustrates this titration with the same alco- 

 holic extract of syphilitic liver (see Fig. 109) : 



TABLE 14. ANTIGENIC TITRATION OF AN ORGANIC EXTRACT 



In this instance 0.15 c.c. of the emulsion represents the antigenic 

 unit. In performing the Wassermann reaction 0.3 or 0.4 c.c. was used, 

 and these amounts were about one-fourth the anticomplementary dose. 



It is not unusual to find cholesterinized alcoholic extract and 

 acetone-insoluble lipoids perfectly antigenic in 0.05 c.c. of a 1:20 

 dilution, and not anticomplementary under 1 or 2 c.c. of a 1:10 dilu- 

 tion. In these instances four times the antigenic dose, or 0.2 c.c. 

 can be used, and yet this amount is at least 10 times smaller than the 

 anticomplementary dose a condition of affairs that constitutes a safe 

 and desirable antigen. 



Each new antigen should be tested with a number of serums and 

 controlled by an older antigen of known value before being finally 

 accepted as satisfactory. 



Antigen containers should be well stoppered and kept in the refrig- 

 erator. Deterioration may set in suddenly, and they should, therefore, 

 be retit rated every few weeks. 



VARIOUS METHODS FOR CONDUCTING THE SYPHILIS REACTION 

 First Method. The simplest technic, and the one best adapted for 

 inexperienced workers, is the original Wassermann reaction, performed 



