CHAPTEE IX 



BACTERIA AND DISEASE 



Growth of Knowledge of Bacteria as Disease Producers — Channels of Infection — 

 How Bacteria cause Disease — Diphtheria: Conditions of Infection— Scarlet 

 Fever, Typhoid Fever, Epidemic Diarrhoea : Conditions of Infection — 

 Suppuration and Abscess Formation — Anthrax — Pneumonia — Influenza — 

 Actinomycosis — Glanders. 



Peobably 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. Indeed, 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 experimentally, and finally, 

 established. 



In the middle of the seventeenth century men learned, through 

 the eyes of Leeuwenhoek, that drops of water contained "moving 

 animalcules." A hundred years later Spallanzani demonstrated the 

 fact that decomposition 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 



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