GENERAL TECHNIC . 439 



minutes or more before receiving the complement the corpuscles 

 become "sensitized," and the amount of complement required for 

 effecting hemolysis will be less than if all three are mixed one after 

 another. If this rule is not adhered to, an error in technic may 

 result. 



HI. Hemolytic Amboceptor. Since the original work of Wasser- 

 mann appeared, the antisheep hemolytic system has been most widely 

 used in experimental investigations. 



Antisheep amboceptor is readily prepared by immunizing rabbits 

 with washed sheep's corpuscles. A simple and efficient method is to 

 give intravenous injections of four doses of 5 c.c. each of a 10 per cent, 

 suspension every three or four days. Other methods and the details 

 of the preparation and preservation of amboceptor are given in Chap- 

 ters IV and V. 



The one objection to the use of the antisheep hemolytic system is 

 the presence, in a large proportion of human serums, of variable amounts 

 of natural amboceptor for sheep's cells. In about 70 per cent, of fresh 

 inactivated human serums sufficient amboceptor is present partially 

 or completely to hemolyze the usual dose of sheep-cell emulsion with 

 the customary amount of guinea-pig complement. In fact, the Bauer 

 and Hecht modifications of the Wassermann reaction utilize this natural 

 amboceptor, but, as will be pointed out further on, this factor is too 

 variable to be employed in conducting the reaction, as non-specific or 

 false positive results are quite likely to occur. 



As has been stated in the preceding chapter, the delicacy and accuracy 

 of any complement-fixation test depend to a large extent upon proper 

 adjustment of the hemolytic system. It will readily be understood that 

 the presence of an unknown quantity of natural amboceptor in a serum 

 is a drawback to accurate quantitative estimations. The importance 

 of this lies in the fact that for some unknown reason an excess of ambo- 

 ceptor may completely hemolyze the corpuscles, even though a small 

 amount of the necessary complement has been specifically fixed by 

 antigen and syphilis antibody. In this manner negative reactions may 

 result with serums that would otherwise show a slight positive reaction. 

 To remove this source of error Noguchi has advocated the use of an 

 antihuman hemolytic system, which renders the reaction more delicate. 

 However, comparative studies between antisheep and other hemolytic 

 systems demonstrate that, with proper technic, the influence of natural 

 amboceptors may be reduced to a minimum and rendered almost neg- 



