120 IMMUNE SERA 



Twice the amount of complement to be used in the 

 test or .2 cc. must have no hsemolytic effect on normal 

 unsensitized sheep cells in 5 per cent dilution. 

 Each serum must be tested with a proper amount of 

 antigen and a known positive patient's serum in 

 order to show that it will fix properly. Each serum 

 must be tested with the proper dilution of ambocep- 

 tor in order to determine if its haemolyzing properties 

 are up to the standard. This is done by placing 

 .1 cc. of amboceptor in a series of tubes and to the 

 first adding .1 of complement to the second .09, etc., 

 down to .01. To each tube is added .1 cc. of 5 per 

 cent sheep cells. At the end of twenty minutes in 

 the water bath at 37 C. all the tubes containing .06 

 and above should be completely haemolyzed. 



When the complement of each pig has separately 

 passed these tests the sera may be pooled and a more 

 exact titration made to determine the hasmolytic 

 unit of the mixture. This is done in just the same 

 way as the above titration but the tubes are kept 

 in the water bath for one hour. The tube containing 

 the least amount of complement which shows com- 

 plete haemolysis at the end of one hour is the unit 

 tube. The amount of complement to be used in 

 the tests is 2| units. If the tube containing .05 cc. 

 complement completely haemolyzes then .125 is 

 the amount to use in the tests. It is more con- 

 venient, however, to change the dilution of the com- 

 plement so that .1 cc. contains 2\ units. This i.<* 



