202 ANTI-BACTERIAL PROPERTIES OF SERUM 



effect is a relatively more severe one than in the case of the 

 bactericidal action ; the haemolytic dose was about 0-007 c.c., 

 yet the dead culture had practically no effect on this small 

 amount, whereas in the bactericidal experiments the same 

 amount of culture would often remove half of the bacteri- 

 cidal effect of 0-1 c.c. of normal serum. 



The general result of these experiments is that, as a rule, 

 0-1 c.c. of a dead bouillon culture of heterologous organisms 

 is requisite in order to produce a distinct fall in the bacteri- 

 cidal action, although in one or two instances 0-01 c.c. is 

 sufficient. On the whole, the amount of heterologous 

 organisms necessary to bring about the result mentioned 

 is much greater than in the case of homologous organisms ; 

 in fact, the results generally would appear to show that, as 

 a rule, it is at least about ten times greater. At first sight 

 it might appear that the explanation would depend upon 

 the presence of an immune-body which is absorbed by the 

 homologous organism ; whereas the heterologous organisms 

 would act by the absorption of complement (which is present 

 in excess in relation to the amount of immune-body) and 

 hence a larger amount of the heterologous emulsion would 

 be necessary. If we regard, however, the whole complement 

 content of the serum, this explanation is not sufficient, for 

 it is quite easy, as has just been shown, to greatly reduce 

 the bactericidal action by means of a heterologous organism 

 without appreciably affecting the haemolytic value. The 

 general results may thus be stated as follows : 



The effect of treating a serum with a given organism in the 

 dead condition is, as a rule, first to reduce the bactericidal 

 action for the same organism ; on increasing the amount of 

 dead emulsion the bactericidal action on other organisms is 

 impaired; on still further increasing the amount of dead 

 emulsion the hcemolytic value falls, and this may be practi- 

 cally exhausted, but in this case a very large amount of dead 

 organisms must be used. It may be stated, further, that 



