THE AGGLUTINATION REACTION 307 



It follows that in the case of inoculated persons the diagnosis of 

 active typhoid (or paratyphoid) infection will require two or more 

 successive examinations of the serum. 



(a) If the individual is suffering from active typhoid infection his 

 titer of typhoid agglutination will exhibit the usual rise and sub- 

 sequent regular fall seen in non-inoculated subjects, but starting 

 from and returning toward the higher base line of inoculated 

 persons. 



(6) If the individual is suffering from active paratyphoid infection 

 one of three things may occur as regards his typhoid agglutination 

 titer, namely: 



1. No appreciable change may occur in the titer of typhoid 

 agglutination. 



2. A relatively slight rise may occur, followed by a fall toward 

 the former level. 



3. A marked rise may occur synchronous with the rise in para- 

 typhoid agglutination titer, and subsequently followed by 

 the usual fall toward the former level. 



Meanwhile the titer of paratyphoid agglutination runs the normal 

 course of rapid rise to a maximum (usually exceeding the maximum 

 typhoid titer), followed by a fall, at first rapid and then slower, as already 

 described for typhoid subjects, and falling below the persistent base line 

 of typhoid agglutination of inoculated persons. 



In the case of mixed infections, whether in inoculated or non- 

 inoculated persons, the agglutinin curves for the different infecting 

 organisms are usually not synchronous, and they pursue their ordinary 

 course independently of each other. 



Technic of Conglutination Test with Bacteria. Fresh bovine serum 

 is heated to 56 C. for one-half hour and tested for agglutinin for the 

 bacteria under study. If agglutinin is present it is removed by adding 

 to each 5 c.c. of serum about 10 loopsful of the corresponding bacteria, 

 mixing well, and removing the clumps by thorough centrifuging and 

 filtration through paper after standing at room temperature for several 

 hours. It may be necessary to repeat this step once or twice more. 



Dilutions of the patient's serum in amounts of 1 c.c. are made in 

 small clean test-tubes, as in the macroscopic agglutination test. To 

 each tube add 0.1 c.c. of bovine serum ("conglutinin") ; 0.1 c.c. of fresh 

 guinea-pig serum (complement) and 0.1 c.c. of the emulsion of the bac- 

 teria of sufficient density to give well-marked emulsions in the test-tubes. 

 Controls of bovine serum, complement serum, and patient's serum 



