116 APPLIED IMMUNOLOGY 



the lieeL The tube containing the blood thus collected 

 should be plugged with cotton and if possible be kept 

 in the refrigerator until required for the test. It 

 will keep well for four or five days in this way, but 

 should be tested as early as possible after removal 

 from the patient. If blood is to be carried or sent any 

 distance, a cork or other impervious stopper should be 

 put in the tube, as inversion would cause the serum to 

 be absorbed by a cotton stopper. The blood if kept 

 too long, or in too high temperature, may heemolyze, 

 and is then unfit for use, though slight hsemolysis does 

 not interfere with the test. Consequently if the serum 

 is to be shipped from a distance or stored miusually 

 long, the serum had best be separated from the clot. 



We now arrive at the procedures to be carried out 

 on the day of the test. They will be given, as far as 

 possible, in the order in which they may be carried out 

 in the shortest possible time. 



Pi^eparation of Comjylement. — The guinea-pig is 

 first of all bled to death in the manner previously de- 

 scribed, so that its serum will have separated by the 

 time it is required. One guinea-pig as a rule will fur- 

 nish sufficient complement for about 40 cases and 

 their controls. The serum is made into a 1 in 10 dilu- 

 tion with normal saline solution for convenience in 

 handling small quantities. 



Preparation of the Suspension of Sheep's Cor- 



