524 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



test. The serum should be inactivated, as active serum is likely to 

 yield non-specific reactions. The primary incubation for complement 

 fixation should be one hour at 38 C. in the water-bath or six hours in 

 the refrigerator at 8 C. 



Practical Value of the Test. Positive reactions are not usually ob- 

 tained until the paroxysmal stage is reached, when about 50 per cent, 

 of sera react positively (Park). For this reason the complement- 

 fixation test possesses little value in early diagnosis. It is at times of 

 value in the diagnosis of atypical cases. 



With rabbit immune sera the test has proved of value in the study 

 and differentiation of microorganisms resembling Bacillis pertussis. 



THE COMPLEMENT-FIXATION TEST IN THE STANDARDIZATION OF 



IMMUNE SERUMS 



The technic of complement fixation has also been employed as one 

 means in effecting the standardization of antimeningococci and anti- 

 gonococcic serums. Since, however, the amount of complement-fixing 

 amboceptors in a serum is no index to its therapeutic and prophylactic 

 value, a measure of this one factor is not a reliable standard. 



The technic consists in preparing the antigen and in determining its 

 anticomplementary dose. Whatever this is, one-half to one-quarter 

 this amount is added to increasing quantities of heated immune serum, 

 ranging from 0.001 to 0.1 c.c. Complement and saline solution are 

 added, and after incubating one hour at 37 C., the amount of comple- 

 ment fixation is determined by adding hemolytic amboceptors and cor- 

 puscles. 



While this titration is one measure of the reaction of the animal used 

 in the immunization, better evidence of the therapeutic value of the 

 serum is obtained by determining the content in bacteriotropins, by 

 testing the serum with the antigen in susceptible animals, or by a com- 

 bination of all methods. 



THE COMPLEMENT-FIXATION TEST IN ECHINOCOCCUS DISEASE 



Several investigators have employed a complement-fixation technic 



in the diagnosis of echinococcus disease of the liver. Ghedini 1 found 



this test of value, and he also reports specific reactions with the sera of 



persons infested with Ankylostoma duodenales and Ascaris lumbri- 



1 Gaz. degli Ospedali e delle Cliniche, 1906, 27, p. 1616; 1907, 28, p. 53. 



