FIXATION OF COMPLEMENT 117 



pnscles. — Sixty c.c. of a 5 per cent, suspension of 

 sheep's corpuscles will usually be found ample for 

 about twenty cases. This suspension is made as de- 

 scribed under the hsemolytic system. The washed 

 corpuscles will keep on ice without deterioration for 

 about three days, after which spontaneous haemolysis 

 usually begins. 



Titration of Complement, — In performing the 

 Wassermann test it is essential that we know the 

 smallest amount of complement that is necessary to 

 produce haemolysis in the heemolytic system. There- 

 fore before coming to the test proper we must each 

 day, first of all, find out the smallest amount of guinea- 

 pig serum in the presence of which 1 c.c. of a 1-1000 

 dilution of amboceptor will heemolyze 1 c.c. of a 5 

 per cent, suspension of sheep's corpuscles. This 

 amount is known as 1 unit of complement, and may 

 vary somewhat in the serum of different guinea-pigs. 

 The employment of not more than one unit of comple- 

 ment in the reaction is of great importance, since an 

 excess might furnish enough to produce complete 

 haemolysis and thus give a negative result when some 

 of the complement employed has been previously 

 fixed by syphilitic serum and antigen. Again, the 

 use of less than one unit of complement would give 

 a positive reaction even in the absence of syphilitic 

 serum, as haemolysis would then be incomplete. The 



