294 Wassermann Reaction for Diagnosis of Syphilis 



ment of the rabbit, and apparently, also, according to the ability 

 of the individual rabbit to respond to the treatment by the forma- 

 tion of hemolytic amboceptors. It is, therefore, imperative to make 

 a careful titration of it. 



To do this we proceed as follows, the quantities recommended 

 being such as experience. has proved most satisfactory: 



Into each of a series of common test-tubes or culture-tubes i cc. 

 of the 5 per cent, suspension of sheep corpuscles and i cc. of the 

 I : lo dilution of the normal guinea-pig serum (complement) are 

 measured with graduated pipettes, and then to each of these tubes 

 the rabbit serum (amboceptor), diluted with physiological salt solu- 

 tion so as to make the correct measurement of the minute quantities 

 necessarily employed a matter of ease and convenience, is added in 

 diminishing quantities for the purpose of determining the least 

 quantity that will bring about complete hemolysis in two hours at 

 the temperature of 37°C. The occurrence of the hemolysis is shown 

 by a very striking change in the appearance of the fluids. The 

 mixture is at first opaque and pale red, but after hemolysis, or solu- 

 tion of the red corpuscles, becomes a beautiful transparent Burgundy 

 wine red. 



The actual "set-up" or working scheme for determining the unit 

 or least hemolyzing addition of the amboceptor serum may be 

 represented as follows, the tubes being placed in a thermostat and 

 observed every fifteen minutes: 



After the reagents are added, enough 0.85 per cent, salt solution 

 is added to each tube to bring the total bulk of the mixture up to 

 S cc. 



From the results shown in the tubes it is evident that the hemolyz- 

 ing quantity of the rabbit serum lies between 0.0005 and 0.0003 

 cc, and is probably 0.0004 cc. To be as accurate as possible, a 

 second series of experiments should be made with 0.0005, 0.00045, 

 and 0.0004 cc, so that the proportion of amboceptor serum neces- 

 sary to effect hemolysis be known within small limits. This least 

 quantity, that will certainly cause hemolysis in two hours at 37° 

 C, is known as the unit.. The combination of the unit of corpuscular 

 suspension (i cc), the unit of complement (o.i cc), and the unit 

 of hemolytic amboceptor is known as the hemolytic system. 



As soon as this unit is known accurately, we are in position to 



