228 BACTERIOLOGY. 



tious disease is caused by a " specifically " 

 characteristic small living thing or mi- 

 crobe. Most of these microbes but not all 

 belong to the group of bacteria. These bac- 

 teria, which are Jrherefore entities altogether 

 external, are, as Koch has set forth with great 

 clearness, the sole true and sufficient cause of 

 the infectious diseases. Differences in these dis- 

 eases are due to differences in the small living 

 things at the bottom of the process, in the dis- 

 ease-producing bacteria alone. In short, bac- 

 teria constitute the " entities " of infectious 

 disease. According to the theatrum diabolo- 

 rum, the view prevailed in the Middle Ages 

 that " every sin is under the control of and 

 operated by a particular devil " ; at present 

 each disease in similar fashion 'has its own 

 devil in the form of a specific bacilliis. Beelze- 

 bub, the god of invisible evil flies, is peculiarly 

 the protecting patron of the " specific " bacteri- 

 ologists. 



' Between this conception a matter in which 

 the French daily press finds its oracle in Pas- 

 teur and the German in Koch and the con- 

 ception of Virchow, there exists a profound 

 antagonism. It is the same conflict that pre- 

 vailed between Liebig and Pasteur over the 

 physiology of fermentation. Liebig sought 

 the cause of fermentation, as Virchow did that 



