174 



THE NEISSER-WECHSBERG PHENOMENON 



(complement) was added, and the mixture made up to constant 

 volume with sterile normal saline solution. It was then incubated 

 for three hours at 37 C., and finally 5 drops from each tube 

 were plated out on agar and incubated. The result is shown on 

 the table. 



This shows that when g-^Vzr c.c. of a one-day-old broth culture was 

 treated with 3 c.c. of fresh normal serum (complement) and in- 

 creasing doses of immune serum, there was no appreciable bacteri- 

 cidal action when more than 0-25 c.c. of the latter was used, or 

 with less than o-ooi c.c. When the amount was between o-i and 

 0-025 c.c., or about 0-0025 c.c., there was appreciable action, and 

 when it was between o-oi and 0-005 c.c. it was complete. 



The same authors also demonstrated a very remarkable phe- 

 nomenon of exactly the same nature. A normal serum which has 

 a certain amount of bactericidal action (owing to the presence of 

 complement and of a small quantity of amboceptor) may have its 

 action increased, diminished, or nullified by the addition of a 

 powerful immune serum. This is shown by the following table, 

 which demonstrates the action of normal guinea-pig serum on 

 V. Nordhafen by itself and after the addition of variable doses 

 of heated immune serum. 



This table shows that there is a definite relation between the 

 amounts of amboceptor and of complement which have to be 

 present to produce a maximal effect. In the case of the normal 

 serum, it is evident that there is more complement than can be 

 used by the amount of amboceptor present, and that the bacteri- 

 cidal action of the mixture increases as immune serum is added. 

 0-05 c.c. of normal serum was without obvious bactericidal effect 

 on c.c. of the culture, whereas the same amount plus 0*01 c.c. of 



