THE TECHNIQUE OF SERUM REACTIONS 307 



Before use the reaction of the meat extract should be tested, and 

 if necessary adjusted to neutrality or slight acidity or alkalinity. 



In the actual test with bacterial filtrate, the procedure is as 

 follows: In a series of narrow test tubes, the following mixtures 

 are made: 



Tube 1. Antibacterial serum .5 c.c. -f bacterial nitrate 1. c.c. 



" 2. Normal serum .5 c.c. + bacterial filtrate 1. c.c. 



" 3. Antibacterial serum .5 c.c. + salt solution 1. c.c. 



" 4. Salt solution .5 c.c. -f- bacterial filtrate 1. c.c. 



Place the tubes in the incubator at 37.5 C. Tube 1 only should 

 show a haziness which develops into distinct cloudiness or a floc- 

 culent precipitate within one hour. Tubes 2, 3, and 4 should remain 

 clear. 



In testing an unknown protein with serum of an animal im- 

 munized with the protein sought for, the technique of the test is 

 as follows: 



1. 0.1 c.c. immune serum + 2 c.c. unknown protein solution. 



2. 0.1 c.c. immune serum + 2 c.c. known protein solution of variety sus- 



pected (similarly diluted). 



3. 0.1 c.c. immune serum + 2 c.c, protein solution of different nature 



(similarly diluted). 



4. 0.1 c.c. immune serum + 2 c.c. salt solution. 



5. 2 c.c. unknown protein solution. 



If the test is positive a precipitate appears in tubes 1 and 2, but 

 not in any of the others. The precipitate should appear within 

 15 to 20 minutes. 



Bactericidal and Bacteriolytic Tests. The bactericidal and bac- 

 teriolytic powers of serum may be tested either in the animal body 

 or in the test tube. The in vivo test is known as Pfeiffer's 

 phenomenon. This depends upon the fact that bacteria, when in- 

 jected into the peritoneal cavity of a guinea-pig, together with a 

 homologous immune serum, undergo dissolution. 



As practiced, the test finds a double application. It may be done 

 to determine the bacteriolytic power of a given serum against a 

 known microorganism, or for the identification of a particular micro- 

 organism by means of its susceptibility to lysis in a known immune 

 serum. 



