SERUM DIAGNOSIS 



471 



The growth is then washed off with salt solution. This salt 

 solution suspension of the organisms is kept at 60 C. for four 

 hours in order to kill the bacteria. The suspension is then 

 placed in a shaking machine and shook at frequent intervals 

 for four days. It is then centrifuged at high speed (3000-5000 

 revolutions per minute), the clear' supernatant liquid drawn 

 off and ten per cent of a 5% solution of carbolic acid added. 

 Before use the antigen must be titrated to obtain its anti- 

 complementary action. It would be well also to determine its 

 antigenic and hemolytic properties as well. However, this 

 may be left until the test proper. 



Titration of the Extract or Antigen. The titration of the 

 extract is carried out in order to determine the quantity of the 

 extract which no longer prevents hemolysis (the anti-comple- 

 mentary action). A 1-10 dilution of the extract is first made 

 by adding 1 cc. of the extract to 9 cc. of salt solution. From 

 this 1-10 dilution other dilutions are prepared as follows. 



TABLE NO. IV. 



DILUTIONS OF THE ANTIGEN. 



