BACTERIOLYSINS AND H&MOLYSINS 119 



injection. The clear serum is bottled in small 

 amounts, sealed and heated to 56 C. one-half 

 hour on three successive days. Its strength is 

 determined by titrating it against i\ units of com- 

 plement and .1 cc. of 5 per cent sheep cells. A 

 preliminary dilution of i to 100 with normal saline 

 is first made and varied amounts of this placed in a 

 series of tubes beginning with .1 cc. then .09, etc., 

 down to .01. With a proper dilution the tube con- 

 taining .05 should completely hasmolyze with 2\ 

 units of complement and .1 cc. of sheep cells, re- 

 sults being read at the end of one hour at 37 C. 

 The dilution must be made weaker if tubes contain- 

 ing less than .05 cc. of amboceptor hsemolyze com- 

 pletely. When the dilution has been found .05 cc. 

 of which causes complete haemolysis the amboceptor 

 is considered to be standardized and three times 

 .05 cc. or 3 units are used in sensitizing .1 cc. of 

 5 per cent sheep, cells. If kept sterile and in a dark, 

 cool place, amboceptor will keep for months. 



Complement. For the preparation of complement, 

 guinea pigs may be killed or bled -directly from the 

 heart with a sterile syringe and allowed to recover. 

 The blood is allowed to clot and the serum which 

 separates centrifuged and made up in a 10 per cent 

 dilution with normal saline. As the complement 

 varies widely in its fixing qualities it is well to use 

 the pooled serum of at least 3 pigs. Each serum 

 must be tested separately before they are mixed. 



