542 CYTOTOXINS 



The Test. To 10 drops of the patient's serum add one drop of 0.5 

 per cent, solution of sodium fluorid. Then add one drop of the cancer- 

 cell emulsion so diluted that when one drop of the mixture is placed in a 

 blood-counting chamber, about 10 to 20 cancer cells will be found in a 

 field of four large squares. Close the counting chamber carefully, ring 

 with vaselin to prevent evaporation, and place in the incubator for 

 twenty-four hours. 



A second slide is prepared from a mixture composed of one volume 

 each of normal serum, cancer serum, and 0.6 per cent, sodium chlorid 

 and sufficient cell emulsion. 



A third slide is prepared with a fresh normal serum in the same 

 manner as when the patient's serum is used. 



All slides are incubated for twenty-four hours at 37 C. and the cells 

 counted. A material reduction in the number of cells with the normal 

 serum will be noted; if the patient has carcinoma, the first and second 

 slides will not show this reduction, whereas if the patient is free from 

 cancer, similar reduc.tions will be found in all three slides. 



The authors recommend that both the cytolytic and the precipitin 

 test be conducted when enough serum is available for both. 



