1 66 THE TECHNIQUE OF COMPLEMENT FIXATION. 



is up. Then instead of adding i c.c. of these ingredients separately, 2 c.c. of the mixture 

 is added to all except tubes 28 to 30. Tubes 29 and 30 receive i c.c. of blood and i c.c. 

 of saline and tube 28 i c.c. of blood, 1/2 c.c. of hemolysin and 1/2 c.c. of saline which 

 have been sensitized. 



The various strengths of the resulting reactions are differentiated as 

 follows : 



a. Tubes i and 2 show complete absence of hemol- i 



ysis: + + + + { Strongly 



b. Tube i shows complete absence of hemolysis and positive. 



2 shows faint hemolysis : + + + 



c. Tube i shows complete absence of hemolysis and 



2 shows complete hemolysis : + + Weakly 



d. Tube i shows partial hemolysis and f positive. 



2 shows complete hemolysis: + 



e. Tube i shows doubtful binding and 1 , r , 



Doubtful. 

 2 shows complete hemolysis : 



/. Tubes i and 2 show complete hemolysis: , Negative. 



When a series of tests is to be performed, it is advisable to include in the 

 reaction three already tested sera, one strongly positive, another weakly 

 positive and a third, negative, so that the new result can be more readily 

 compared. In this way absolutely reliable and constant values will be 

 obtained. 



Every new antigen should be tested for four weeks before its practical value can be 

 assured. During this month, all the tests should be done with both the old and new ex- 

 tract and only if their results are equal should the new extract be employed. The author 

 is in the habit of mixing the new antigen with the old one after the former has proved 

 itself efficient. Occasionally the new antigen varies in strength from the old one. In 

 such a case, if stronger, it must be used in a smaller dose (0.18 and 0.9) or if weaker, 

 must be used in larger dose (0.22 and o.n). Shaking up of the antigen should be 

 strictly guarded against. 



In order to control the effect of normal liver substances contained in the antigen, an 

 extract is prepared in an analogous method from normal fetal liver (normal antigen). 



A strongly positive Wassermann reaction indicates the presence of a 

 luetic infection. A weakly positive result can be similarly interpreted if the 

 serum control tube (Tube No. 3) is completely hemolysed. If, however, the 

 latter still shows some non-hemolysed red blood cells, the + reaction must 

 be considered as or a reaction of indefinite nature. Only exceptionally are 

 such doubtful reactions found in perfectly healthy individuals, although 

 they are more often encountered in different infectious diseases (typhoid, 

 measles, scarlet) and tumors. A positive diagnosis of lues should never be 

 made upon a reaction. On the other hand if there is a history of lues, or 

 clinical evidences of the same, a reaction is to be interpreted as + and 

 should warrant further specific therapy. As an end result of specific therapy 



