210 APPENDIX 



Weil's Cobra Venom Test in Syphilis 



In studying the varying resistance of red blood 

 corpuscles to haemolytic agents, Weil 1 noted that 

 the corpuscles of syphilitics were regularly more 

 resistant to the action of cobra venom than those 

 of normal individuals. Just what is the cause of 

 this increased resistance is not entirely clear. It 

 is known that syphilis attacks the lipoids of the 

 body, and that the amount of lecithin which can 

 be extracted from the tissues is less in syphilitic 

 conditions than in normal individuals. The in- 

 creased resistance has therefore been thought to 

 be due to a decrease in the lecithin content of the 

 red blood corpuscles. 



In testing the corpuscles the blood is collected 

 in citrated salt solution, and then washed by 

 repeated centrifugalization in order to thoroughly 

 remove the serum. Even slight traces of 

 serum interfere decidedly with the reaction. The 

 washed cells are made up into a four per cent 

 suspension in 0.9 per cent common salt solution. 

 Centrifugalization is done in very accurately grad- 

 uated centrifuge tubes, as the accurate dilution of 

 the cells is a matter of very great importance. 

 The cobra venom, which is kept in the dried con- 



1 Weil, Richard, Journal of Infectious Diseases, Vol. vi, Nov., 

 1909. Proceedings Society Exp. Biology and Medicine, Vol. vi 

 and Vol. vii. 



