314 PRECIPITINS 



Tube 4: 2 c.c. of typhoid bouillon filtrate+1 c.c. of unknown serum. 



Tube 5: 2 c.c. of typhoid bouillon filtrate+1 c.c. of typhoid im- 

 mune serum (positive control). 



Tube 6: 2 c.c. of typhoid bouillon filtrate+1 c.c. of normal salt 

 solution. 



Tube 7: 2 c.c. of typhoid bouillon filtrate+1 c.c. of normal serum. 



Tube 8: 1 c.c. of serum +1 c.c. of normal salt solution. 

 The tubes are not shaken, and are kept at room temperature for 

 from one to six hours. If the unknown serum contains considerable 

 typhoid precipitins, a positive reaction will be noticed in the first four 

 tubes in a short time often within from ten to fifteen minutes. Tube 

 5 should show a strong reaction and the other tubes should remain clear. 

 In studying the biologic relationship of an organism to others of the 

 same group its immune serum may be used in amounts of 1 c.c. of vary- 

 ing dilutions, as 1:50, 1:100, 1:500, 1:1000, 1:2000, 1:4000, and 

 so on, with a constant dose of 1 or 2 c.c. of the bouillon filtrates of the 

 various organisms studied. A comparison of the precipitates in the 

 respective dilutions of the different filtrates indicates the relationship, 

 according to the amount of group precipitins present in the immune 

 serum. 



PRECIPITIN TEST IN CANCER 



Freund and Kaminer have devised a precipitin test to be used in 

 conjunction with their cytolytic reaction in the diagnosis of cancer. 

 The extract of cancer-cells is prepared by treating fresh tissue or tissues 

 preserved in alcohol, finely minced with 10 volumes of 0.6 per cent, acid 

 sodium phosphate solution. After agitating the mixture the cells are 

 allowed to settle, and the extract is decanted off and preserved in an ice- 

 chest, a few crystals of thymol being added as a preservative. For use 

 add 5 c.c. of a 5 per cent, acetic acid solution to 100 c.c. of the fluid; 

 heat the mixture in a water-bath for fifteen minutes at 80 C., and filter. 

 Cool, and neutralize to litmus with sodium carbonate. Heat again 

 as previously directed, cool, and filter. The extract may now be tested 

 undiluted, and diluted 10, 50, and 100 times with 10 drops of known 

 normal and cancerous serums, the latter yielding a precipitate that is 

 plainly visible in test-tubes held against the light. The extract keeps 

 for only a few days. 



The dilution of extract that yields a precipitate with known can- 

 cerous serum, but not with a normal serum, is used in testing unknown 

 serums. Place 10 drops of the patient's serum in a small test-tube and 



