THE TECHNIQUE OF SERUM REACTIONS 321 



III. The Complement. The complement used in Wassermann 

 reaction is fresh guinea-pig serum. This may be obtained in one of 

 the following ways : A guinea-pig may be killed by an incision in the 

 throat and the blood allowed to flow into a large Petri dish. This is 

 set away in the ice chest until clear beads of serum have formed 

 upon the surface, and these are then carefully removed with a 

 pipette. 



It is more economical to puncture the heart of large guinea-pigs 

 with a needle attached to a syringe and withdraw 5 or 6 c.c. of blood 

 without killing the animal. This can be transferred to a centrifuge 

 tube and the serum obtained by centrifugation after clotting. Serum 

 used as complement in the Wassermann reaction must be titrated each 

 day before reactions are done. This is done by putting into a series 

 of tubes 1.0 c.c. (or if half quantities are used, as with us, 0.5 c.c.) 

 of the cell suspension sensitized with 2 units of amboceptor, and 

 adding to these tubes varying quantities of guinea-pig serum. The 

 guinea-pig serum is best diluted 1 :10 in salt solution, and quantities 

 ranging from 0.05 to 0.35 c.c. are added to the tubes. The unit is the 

 amount in the tube which shows complete hemolysis at the end of an 

 hour. The reactions are usually complete in about 30 minutes. Two 

 units of the complement are used in the ordinary test. The titration 

 of the complement is one of the most important steps in accurate 

 work. 



IV. The Sheep Corpuscles. The sheep corpuscles for the actual 

 reaction are obtained by receiving the blood in a small flask containing 

 a sterile solution of a 0.5 per cent sodium citrate and 0.85 per cent 

 sodium chloride, or into one containing glass beads or short pieces of 

 glass tubing. In the former case, the citrate solution prevents clotting 

 and the corpuscles may be washed free from the citrate solution and 

 emulsified in salt solution before use in the test. In the latter case, it 

 is necessary to shake the blood in the flask immediately after taking, 

 and to continue the shaking motion for about ten minutes. The cor- 

 puscles are washed free from serum by at least 3 washings in salt 

 solution. A 5 per cent suspension of the corpuscles is employed for 

 the test, made by measuring the bulk of centrifugalized corpuscles and 

 adding nineteen parts of sterile salt solution. 



V. The Serum to be Tested for Syphilitic Antibody. The serum of 

 the patient is best obtained in the same way that blood is obtained for 

 blood cultures. After . surgical precautions, a needle is plunged into 

 the median basilic vein and 3 or 4 c.c. of blood are removed. Before 



