APPENDIX 211 



dition, is made up very accurately in small quan- 

 tities into a 0.05 per cent solution in 0.9 per cent 

 solution of common salt. From this stock solution, 

 higher dilutions are prepared as required, and are 

 kept at a constant low temperature. In carrying 

 out the test four solutions are prepared, namely, 

 i in 10,000, 20,000, 30,000, and 40,000. One cc. 

 of the corpuscle suspension is added to one cc. of 

 the venom solution. The mixtures are incubated 

 for one hour at 40 C., after which a preliminary 

 inspection will almost invariably reveal the final 

 results of the tests. At this stage, cells showing 

 no haemolysis with i to 10,000 venom are strongly 

 positive, cells showing no haemolysis with i to 

 20,000 are positive, cells showing very slight hsemol- 

 ysis at i to 30,000 are weakly positive; cells show- 

 ing moderate destruction at i to 30,000 are negative, 

 and cells showing the least appreciable trace of 

 haemolysis at i to 40,000 are strongly negative. 

 After the preliminary reading the mixtures are 

 again shaken and then kept in the ice-box over 

 night, the final readings being made on the follow- 

 ing morning. The figures here given are merely 

 those of a particular specimen of cobra venom; 

 it is possible that other samples might differ in 

 strength. At all events a preliminary titration 

 against corpuscles derived from cases of known 

 syphilis and controls suffices to determine the 

 values for any given sample. Inasmuch as the 



