426 Mr. H. B. Dean. [Oct. 13, 



culture of B. typhosus were used. Such an experiment is represented 

 in Table V. 



Table V. 





- 5 c.c. of inactivated 

 diluted antityphoid 



A. 



+ 1 c.c. normal 



+ 0-5 c.c. middle- 

 piece 1 — 10, 

 and -5 c.c. normal 

 saline. 



c. 



+ 0-5 c.c. middle- 

 piece 1—10, 

 and "5 c.c. end -piece 

 1—10. 



1 



1 in 4000 



+ + 



+ + + 



+ + + 



2 



1 in 5000 



+ 



+ + + 



+ + + 



3 



1 in 6000 







+ + 



+ + 



4 



1 in 7000 









+ + 



5 



1 in 8000 







+ 





6 



1 in 9000 

















Controls 









7 



0'5 c.c. normal saline 















Every tube contained 2 c.c. In the control tubes the bulk was made up to 2 c.c. with normal 

 saline. Tube 7 contained in column A 0'5 c.c. of bacillary emulsion and l - 5 c.c. of saline ; in 

 row B emulsion and middle-piece ; in row C emulsion and middle-piece and end-piece. In these 

 controls no agglutination was observed. In row A the agglutinative power of the immune serum 

 is recorded. No agglutination was observed below tube 2. It will be seen that this tube 

 contained 5 c.c. of emulsion of bacteria, 0'5 c.c. of a 1 in 5000 dilution of antityphoid serum, 

 and 1 c.c. of normal saline solution. The ultimate dilution of the immune serum was in conse- 

 quence 1 in 20,000. Column B shows the agglutination produced by immune serum in the same 

 dilutions plus 05 c.c. of a 1 in 10 dilution of middle-piece in every tube. All the tubes were 

 incubated for 4 hours at 37° C. 



Remarks on Table V, 



It will be seen that the agglutinative power of the immune serum is 

 increased by the addition of middle-piece. The result of the addition of end- 

 piece to middle-piece and immune serum is shown in Column C. No further 

 increase in agglutination was observed. Numerous experiments were made 

 which gave results consistent with those shown in Table V. 



To demonstrate the effect of middle-piece solution it is necessary to dilute 

 the immune serum to such an extent that its agglutinative power is just 

 beginning to disappear. The action of such diluted antiserum can be increased 

 by the addition of middle-piece solution. Further, the agglutinative power 

 of an antiserum which has been diluted beyond the point at which the agglu- 

 tination can be appreciated, can be restored by the addition of the middle- 

 piece solution. 



These experiments show that there exists in normal guinea-pig serum 

 some substance which increases the agglutinative action of antiserum. This 

 substance is thermostable, and probably has no connection with complement. 

 It can be separated from serum with the fraction of the globulins which are 



