INFECTION AND IMMUNITY. 541 



the characteristic tissue death, but it is less in evidence 

 and it is not progressive beyond certain limits and the 

 injection does not necessarily prove fatal to the animal. 

 As a result of this experiment we see that dead bacteria 

 may produce a result differing only in degree from that 

 caused by the same species when living and fully 

 virulent. 



A similar property may be demonstrated in a number 

 of other pathogenic species in no way related to bacillus 

 tuberculosis. Obviously, there is something within or 

 associated with these bacteria that may act upon the 

 tissues even though the bacteria themselves may be 

 dead. 



In our autopsy on the animal dead of diphtheria we 

 saw that the bacilli were not distributed throughout the 

 body, but were confined to the site of inoculation. We 

 saw at the site of inoculation a tissue reaction scarcely 

 sufficient to account for the fatal result, yet that result 

 occurred within a comparatively short time following 

 inoculation. 



When diphtheria occurs in human beings the same 

 holds true as a rule, and while occasionally the local re- 

 action in the throat is such as gravely to imperil life 

 through obstruction to respiration, the real danger in 

 most cases is not local but remote, and the clinical 

 observations on the living subject affected with this dis- 

 ease point to the far-reaching influence of a local phe- 

 nomenon, that, of itself, may often seem to be of but 

 slight significance. 



If the internal organs of either animals or human 

 beings that have died of diphtheria be examined micro- 

 scopically, changes are easily to be discovered that are 



