482 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



At the end of the second incubation, or after two hours more at room 

 temperature, the tubes are inspected. The antigen and hemolytic 

 system controls, as well as all the rear tubes or serum controls, should 

 be completely hemolyzed. The first tube containing a known syphilitic 

 serum shows inhibition of hemolysis; the front tube containing normal 

 serum is completely hemolyzed; the front tube containing the patient's 

 serum shows complete inhibition of hemolysis (strong positive), varying 

 degrees of inhibition (moderately or weakly positive), or is completely 

 hemolyzed (negative). The results may be recorded and reported after 

 the same manner described on p. 464. 



MODIFICATION OF CRAIG 



Craig 1 employs a technic differing from the original Wassermann 

 reaction in the use of a human hemolytic system in place of a sheep 

 hemolytic system, and in a proportional reduction in the quantities 

 of reagents used. Alcoholic extract of syphilitic liver is generally em- 

 ployed as antigen, although cholesterinized extracts of normal heart 

 muscle have been found equally satisfactory. 2 Vedder 3 has also used 

 Craig's method in standardizing the Wassermann reaction for use in the 

 military service, and it is widely used in the Army with satisfactory 

 results. 



MODIFICATION OF BAUFJ?. 



Bauer does not use rabbit-sheep amboceptor, but takes advantage 

 of the antisheep amboceptor normally present in variable amounts in a 

 large proportion of human serums. Although this test is quite delicate, 

 the quantity of natural amboceptor in human serums is too variable a 

 factor to be depended upon, and the modification is not, therefore, in 

 general use. 



MODIFICATION OF HECHT-WEINBERG-GRADWOHL 



In conducting the syphilitic reaction Hecht 4 utilizes not only the 

 natural antisheep amboceptor in human serum but also the native 

 hemolytic complement. The serum must be perfectly fresh and, of 

 course, is used unheated. This modification has been said to be more 

 delicate than the Wassermann reaction because none of the syphilis an- 

 tibody is destroyed or complementoids produced, as presumably will oc- 

 cur during inactivation (heating) of a serum. In my experience this test 



1 War Department, Bulletin No. 3. 



% 2 Amer. Jour. Med. Sci., 1915, cxlix, 41. 



3 War Department, Bulletin No. 8. 

 4 Wien. klin. Wchnschr., 1909, xxii, 265. 



