CHAPTER VIII 



BACTERIA AND DISEASE 



PROBA-BLY the most universally known fact respecting 

 bacteria is that they are related in some way to the 

 production of disease. Yet we have seen that it was not as 

 disease-producing agents that they were first studied. In- 

 deed, it is only within comparatively the latest period of the 

 two centuries during which they have been more or less 

 under observation that our knowledge of them as causes of 

 disease has assumed any exactitude or general recognition. 

 Nor is this surprising, for although an intimate relationship 

 between fermentation and disease had been hinted at in the 

 middle of the seventeenth century, it was not till the time 

 of Pasteur that the bacterial cause of fermentation was ex- 

 perimentally and finally established. 



In the middle of the seventeenth century men learned, 

 through the eyes of Leeuwenhoek, that drops of water con- 

 tained ' ' moving animalcules. ' ' A hundred years later 

 Spallanzani demonstrated the fact that putrefaction and 

 fermentation were set up in boiled vegetable infusions when 

 outside air was admitted, but when it was withheld from 

 these boiled infusions no such change occurred. Almost a 

 hundred years more passed before the epoch-making work 

 of Tyndall and Pasteur, who separated these putrefactive 

 germs from the air. Quickly following in their footsteps 

 came Davaine and Pollender, who found in the blood of 

 animals suffering from anthrax the now well-known specific 



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