SYPHILIS . 125 



tact with the mixture of serum and antigen. Continue the 

 incubation, and after a few minutes stir by inserting the 

 pipette and blowing a few bubbles of air through the fluid, 

 or by sucking it into the pipette and expelling it once or 

 twice. In five minutes more read off the result. If there is 

 complete haemolysis in all the tubes, you may safely use a 

 stronger antigen, and your results will be more sensitive 

 by so doing: re-test with an antigen of a strength of I in 9. 

 If some of the tubes show complete haemolysis and others 

 haemolysis which is very nearly complete, the antigen is of 

 suitable strength. You will, of course, put up a parallel 

 series of tubes as controls, putting in each i volume of serum 

 and 4 of saline. All these should show complete haemolysis. 



2. Emulsion of Corpuscles. The method of washing the 

 corpuscles has already been described. Prepare a 20 per cent, 

 emulsion by taking- i unit of the firmly packed deposit in your 

 pipette, and then 4 units of normal saline. (If greater 

 accuracy is required, perform the last, centrifugalization in a 

 graduated tube, let the process go on until the deposit does 

 not get smaller after additional centrifugalization, pipette off 

 the supernatant fluid, and read off the volume of the corpuscles. 

 Add four times this volume of saline, and stir well.) 



3. The Amboceptor. The preparation of this material 

 requires a vivisection licence. It is made by injecting washed 

 human corpuscles into a rabbit. The corpuscles are usually 

 prepared from blood taken from the arm, or from placental 

 blood, and must be washed with normal saline in the centri- 

 fuge at least three times. Then a mixture of equal volumes 

 of corpuscles and saline is prepared and injected intraperi- 

 toneally into a large rabbit, 20-30 c.c. or more being given at 

 each dose. Two or three doses are usually required, and they 

 are given at intervals of seven to ten days. At this period, 

 after the last injection, the rabbit is bled to death aseptically, 

 the blood allowed to clot, and the serum potted off aseptically 

 into sterile ampoules, about J c.c. in each. Not all rabbits 

 will give a potent serum, and when a rabbit has not responded 

 properly to three injections, it may as a rule be regarded as 

 useless for the purpose. 



Standardization of the Amboceptor. I find that some 

 workers have failed to get satisfactory results with my tech- 

 nique, ^ solely because they have used amboceptor which was 



