142 



BACTERIOLYSINS AND HEMOLYSINS 



Topfer and Jaffe pour a thin layer of agar into a petri dish and let it 

 harden. Upon this the culture-serum- agar mixture is poured, and after 

 hardening is covered with another thin layer of agar. In this way the 

 formation of a film of culture in the water of condensation is avoided. 



A practical example is appended to illustrate the plate culture method. 



In addition to the results which one would expect, this experiment shows one strik- 

 ing point. With the normal serum the tube which contains the largest amount of 

 normal bacteriolysins shows, on plating, the fewest germs. The greater the dilution of 

 the serum the more prolific is the bacterial growth. The titer of the normal serum in 

 this case lies between i/ioo and 1/500. The controls show that the serum and comple- 

 ment are sterile, and that the inactive normal serum is ineffective. During the three 

 hours in the thermostat the bacterial suspension has become stronger. The retarded 

 growth in the complement culture tube can be traced probably to the presence of 

 normal bacteriolysins. 



With the immune serum, on the other hand, results are quite different. Where 

 the most concentrated serum is used, the bacterial growth is still rather profuse; only 

 the moderate doses show a true bactericidal action and the small doses are altogether 

 ineffective. The titer of this serum is between 1/30,000 and 1/40,000. 



Neisser and Wechsberg explain this phenomenon by the so-called 

 ''deviation of the complement." They assume that in the serum of higher 



