CHAPTER XIX. 



Bacteria of the Mouth. 



The Mouth a Good Forcing Ground for Bacteria — Food Material — Kinds 

 of Bacteria found in the Mouth by Miller and Vignal — Bacteria in the 

 Teeth in Caries, in Milk Teeth, and in Abscesses — Combination of 

 Lactic Acid with Lime Salts — Organisms Attack Decalcified Base 

 Substance — Artificial Decay — Mode of Invasion 6f Teeth by Bacteria 

 — Poisonous Saliva — Micrococcus of Sputum Septicaemia — Pneumo- 

 coccus — Other Organisms found in the Mouth — Septicaemia following 

 Slight Operations in the Mouth. 



It will be remembered that many of Leeuwenhoek's obser- 

 vations as to the morphological appearances of the minute 

 structures which he examined with his wonderful lenses, 

 were made on bacteria which were found adhering to the 

 teeth, and certainly some of his most interesting observations 

 were on bacteria derived from this source. From what we 

 now know of the biology of these organisms we can readily 

 understand that the mouth should form a kind of hothouse 

 or forcing-ground for their cultivation. Here is a moist 

 cavity kept at a comparatively high temperature, covered 

 with an epithelium which is constantly being partially or 

 completely shed, to which there is ready access from the out- 

 side air, and through which food material is constantly 

 being passed, particles of which, despite the exercise of the 

 greatest care and the utmost cleanliness, always remain in 

 small crevices between the teeth, or perhaps, more important 

 still, between the gums and the teeth. It is also said that the 

 fact that starch is constantly being converted into sugar by 

 the ptyalin is in favour of the growth of bacteria. Then we 

 have the dead epithelium, which is readily attacked by 

 organisms of various kinds, supplying proteid or other 

 nitrogenous materials ; as a matter of fact, there are often 

 found in these dead epithelial cells a number of micrococci, 

 which appear to be gradually disintegrating their substance 

 and utilizing the materials of which they are composed. In 



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