114 CLINICAL BACTERIOLOGY. 



etc. ; but even in these cases experiments on animals 

 are not useless, for they demonstrate the toxic activity 

 of the bacteria in question, and they lead, above all, to a 

 knowledge of the anti-bodies formed in the blood-serum. 

 Also, the other of Koch's postulates that a microbe, to be 

 considered as the cause of a disease, must be present only 

 in association therewith is not fulfilled in certain diseases. 

 Those infections that are due to the bacteria giving rise to 

 inflammation and suppuration are sometimes caused by the 

 one and sometimes by the other of these germs. The 

 clinical picture of these diseases depends less upon the 

 species of infecting bacteria than upon the site at which the 

 infection is localized. This is true of otitis media, of men- 

 ingitis, of empyema, etc. ; at least, we are as yet not in a 

 position with regard to these diseases to set up different 

 clinical pictures in accordance with the various bacterial 

 findings. A streptococcus-meningitis is clinically not 

 sharply differentiated from a pneumococcus-meningitis or 

 from a meningitis caused by staphylococci, etc. The con- 

 ception of the specificity of bacteria, which is . otherwise 

 fully applicable to the etiology of infectious diseases, must 

 be abandoned with relation to these common excitants of 

 inflammation. 



