﻿320 STRONG. 



Therefore, my experiments would appear to confirm the earlier sug- 

 gestions of E. Pfeiffer that the immunizing power of the plague organism 

 is, within certain limits, proportional to its virulence. However, as my 

 work relating to this question was performed with only three strains of 

 the pest bacillus, it can not be considered to be conclusive for this 

 organism in general and it can merely be stated that with the strains 

 which I have studied, the more virulent organism gave rise to the greater 

 immunity, and that the immunity within certain limits was proportional 

 to the dose. (See experiments, pp. 199 to 221.) 



