COMMUNICABLE DISEASES 393 



that the quantity used will not hemolyze i.o cc. of a 5 per cent, suspension 

 of washed lamb's blood-corpuscles in the presence of 0.2 cc. of a known 

 positive serum, o.i cc. of complement, and 2 minimal units of the hemoly- 

 tic serum. The unit is determined as follows: A series of test-tubes are 

 prepared each containing the same quantities of the reagents mentioned 

 above and varying amounts of the antigen. The usual technic is followed 

 and the unit determined by the quantity of antigen that inhibited hemoly- 

 sis. After this determination the same antigen must be tested with a 

 known negative serum used in place of the positive serum and using double 

 the unit of antigen. This double unit should not inhibit hemolysis of 

 the blood cells. The unit being determined, the antigen is so diluted that 

 i.o cc. will contain the unit. 



2. Antibody. The blood serum or cerebrospinal fluid of the syphilitic 

 person. A sufficient quantity of the patient's blood is collected from the 

 lobe of the ear or finger tip, in any sterile vial (best in a Wright's capsule), 

 aseptic precautions, of course, being observed. The blood is then 

 centrifugalized and the serum used. The spinal fluid is obtained in the 

 usual manner by lumbar puncture. 



3. Complement. The normal blood serum of a guinea-pig. The blood 

 from one guinea-pig is required, thus making it necessary to sacrifice one 

 animal for each test. The blood must be used fresh, as the serum loses its 

 complementing value if kept over twenty-four hours. The blood is defibri- 

 nated, centrifugalized, and the serum used. If stored, it should be frozen. 



4. Hemolytic Serum. The blood serum of a rabbit that has been 

 injected with washed lamb's blood-corpuscles. The rabbit is immunized 

 as follows: The lamb's blood is first obtained, best by cutting its ear and 

 allowing 10 cc. of blood to run into 30 cc. of a i per cent, sodium citrate 

 solution in normal salt solution. (This will prevent the blood from clott- 

 ing). It is then centrifugalized, the supernatant fluid pipetted off, and 

 the blood-corpuscles washed with normal salt solution by repeated centri- 

 fugalization and dejection of the supernatant fluid. Five cc. of the 

 washed blood-corpuscles are injected into the rabbit five (5) or six (6) 

 times at repeated intervals of five (5) days. On about the tenth day after 

 the last injection, blood is taken from the rabbit, centrifugalized, and the 

 serum used. Before using this serum, it is necessary to test its power 

 after being inactivated (heated for threequarters of an hour at 56 C. 

 to destroy complement). The test is made to determine the minimum 

 quantity of the serum that will hemolyze i cc. of the 5 perfcent. suspension 

 of lamb's blood-corpuscles, with o.i cc. of complement (normal guinea- 

 pig serum). Various quantities of the serum to be tested are put in a 

 series of test-tubes with i cc. of the suspension of lamb's blood corpuscles 

 and o.i cc. of the complement in each tube. The tubes are put in the 



