THE TECHNIQUE OP SERUM REACTIONS 267 



neck to lay bare the carotid artery and, severing this, to allow the blood 

 to flow into a sterile centrifuge tube. When clotting has occurred, the 

 clot is loosened from the glass with a platinum needle and the serum 

 separated by centrifugaKzation. Such serum should be used for no 

 longer than three days after being taken and should be kept, except 

 when in actual use, at a low temperature. The complement in 

 guinea-pig serum is sufficiently constant in quantity for practical 

 purposes. 



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

 reaction are obtained by receiving the blood of a sheep 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. At the end 

 of this time, the blood will be defibrinated and the corpuscles are washed 

 free from serum by centrifugalization in salt solution. A 5 per cent 

 emulsion of the corpuscles in salt solution is employed for the test, 

 made by measuring the bulk of centrifugalized corpuscles and adding 

 nineteen parts of sterile salt solution. Thorough washing of the cor- 

 puscles is essential both in order to preclude the occurrence of pre- 

 cipitates and to remove any traces of complement present in the serum. 



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

 the patient upon whom the test is to be made is best obtained in the 

 same way that blood is obtained for blood cultures. After surgical 

 precautions as to sterilization, a needle is plunged into the median 

 basiHc vein and 3 or 4 c.c. of blood are removed. Whenever circum- 

 stances do not permit such procedure, blood may be obtained from the 

 finger or the ear, always in sufficient quantity to furnish at least 1 c.c. 

 of clear serum. Before use for the test, the patient's serum must be 

 inactivated by heating in a water bath to 56° C. for twenty minutes 

 to half an hour. As, according to some observers, 56° C. destroys 

 the syphiUtic antibody in part, Noguchi advises inactivation at 

 54° C. 



The Test. — The actual test for antibody in a suspected serum is 

 carried out in the following way: In a test-tube of suitable size, 0.1 c.c. 

 of complement, 0.2 c.c. of the inactivated suspected serum, and the 



antigen, in quantity determined by titration, are mixed, and th"} total 



18 



