FIXATION OF COMPLEMENT 95 



covery by Wassermann and Bruck that extracts fur- 

 nished by lysis of the bacteria will sei^'e as antigens 

 for the complement -fixation reaction equally as well 

 as, if not better than, suspensions of the bacteria them- 

 selves. This fact was applied by the workers men- 

 tioned in the diagnosis of typhoid fever, tuberculosis, 

 meningitis, etc. 



The Wassermann Reaction 



A further step was now taken by Wassermann, 

 Neisser, and Bruck. They recognized what an enor- 

 mous value the reaction would have if it could be ap- 

 plied to syphilis, the causative organism of which had 

 not been artificially cultivated up to that time (1906) . 

 So these observers conceived the idea of employing as 

 antigen, extracts of organs kno\\Ti to be rich in tre- 

 ponemata (spirochastae). From this the now uni- 

 versally used and important " Wassermann reaction " 

 had its origin. In their first experiments Wassermann, 

 Neisser, and Bruck made water}^ extracts from syphi- 

 litic fetal liver, in which Treponemata pallida are very 

 abundant. Using these extracts they obtained fixa- 

 tion of complement with the sermn of syphilitic in- 

 dividuals, and from their results concluded that the re- 

 action was specific, just as that obtained in the case of 

 typhoid bacillus extract and typhoid serum. But it 

 was then found that alcoholic extracts of syphilitic tis- 



