198 ANTI-BACTERIAL PROPERTIES OF SERUM 



organisms comparatively resistant to guinea-pig's comple- 

 ment. It seems, in view of many other experiments of 

 similar nature, that we must suppose the existence of varia- 

 tions in the resisting power of organisms in the same culture 

 (typhoid) a circumstance of considerable importance. 



EXAMPLE 4. Bacillus enteritidis (Gaertner). Inoculation with 

 0-00005 c.c. 24-hour bouillon culture of B. Gaertneri. 



Here again 0-01 c.c* has a distinct effect ; results with 0-001 c.c. 

 were negative. 



It will thus be seen that in two cases distinct reduction of 

 bactericidal action was brought about by 0-001 c.c. of dead 

 bouillon culture, in two others by 0-01 c.c. It may be 

 noted that there exist great variations in the proportion 

 between the amount of organisms killed and the amount of 

 dead culture necessary to affect the result. For example, 

 with V. Metchnikovi this proportion is 1 to 2. In the case of 

 B. Gaertneri it is 1 to 200. The results would on the whole 

 go to show that the more readily an organism is killed the 

 more easily is the result affected by previous treatment with 

 homologous culture. This might possibly be due to the pres- 

 ence of a small amount of natural immune-body necessary 

 for the process of killing, but readily absorbed by the dead 

 culture. The subject is one, however, which involves 

 theoretical considerations of much difficulty, and cannot at 

 present be profitably discussed. 



