TO DEMONSTRATE THE PRECIPITIN TEST 321 



McCampbell's Modification of the Opsonic Test. 1. 



Prepare the bacterial suspension as above and add 0.8% 

 sodium citrate. 



2. (a) With a blood diluting pipette, draw the bacterial 

 suspension up to the mark 0.5. 



(6) With the same pipette draw up the same amount 

 of blood collected from the patient, then draw both into the 

 bulb and mix quickly. 



(c) Place a flat rubber band around the ends of the 

 pipette and incubate fifteen minutes. Prepare film, and 

 stain. 



3. Repeat the experiment, using normal blood. The 

 opsonic index is determined as above. 



Note. The sodium citrate is slightly antiopsonic but this factor 

 is constant in both preparations, consequently the results are com- 

 parable. 



4. Give results and any conclusions in detail. 



REFERENCES 



McCAMPBELL: Laboratory Methods for the Experimental Study 



of Immunity (1909), pp. 44-70. 



MCFARLAND: Pathogenic Bacteria and Protozoa, 7th Ed., p. 307. 

 KOLMER: Infection, Immunity and Specific Therapy, pp. 187-205. 

 ZINSSER I.e. Exercise 10, p. 318. 



EXERCISE 12. TO DEMONSTRATE THE PRECIPITIN 



TEST 



This test is of importance in identifying the source of 

 blood in legal cases and may also be used in the examina- 

 tion of various meat products for the presence of foreign 

 meat substances. 



It is based upon the fact that if an animal is injected 

 at intervals of six to eight days for four or five times with 

 any foreign protein its serum acquires the property of pre- 

 cipitating that specific protein even when in a very high 

 dilution. 



