34 2 BACTERIA. 



part of the softened area. It was at one time stated that 

 the " leptothrix buccalis," as it was called, was the organism 

 that was always found in these cases, but this is now known 

 not to be the case : micrococci, leptothrix threads, bacilli, and 

 spiral forms may all be met with even in the same decayed 

 tooth, and in tubules lying close together ; the softening and 

 absorption going on indiscriminately, whichever of the organ- 

 isms may be attacking the basic substance. It is owing to the 

 peptonizing power of these organisms that they are able to 

 carry on the disintegrating process, and we thus see that 

 although the bacilli may not be actually present in all parts 

 of a decaying area, their products, such as lactic acid and the 

 peptonizing enzyme, are really carrying on the work that 

 ends in the decay of the tooth, perhaps considerably in 

 advance of the bacteria themselves. In experiments carried 

 on with the object of proving that decay might take place 

 in teeth removed from the mouth, Miller placed a number 

 of perfectly sound teeth in a mixture of saliva and bread ; 

 this mixture was renewed from time to time, whenever the 

 slightest trace of alkalinity appeared, and the pulpy mass in 

 which the teeth were embedded was kept at a temperature 

 of 37 C. during a period of three months, with the result 

 that the dentine became softened, and there was what he 

 describes as a condition of " white decay " ; he found that 

 where the enamel was perfect, even acids had no power to 

 attack the dentine beneath, but in those cases where the 

 enamel was soft or imperfectly developed the dentine had 

 become softened by any acid that was present, and the 

 canaliculi were filled with bacteria ; this gave rise to 

 irregular erosion of these canals which thus appeared to be 

 unequally distended. Near the surface of the tooth the 

 organisms are not strictly confined to the tubules, but they 

 invade the basic substance from the surface, softening it as 

 they advance, but filling up the microscopic cavities as they 

 are formed. 



The organisms described by Galippe and Vignal that were cultivated on 

 gelatine were six in number, all occurring in decaying teeth. 



i. A short thick bacillus i.5/i in length, and nearly as broad as long ; it 

 grows somewhat rapidly on gelatine, giving rise to an opaque white growth 

 along the track of the needle ; it liquefies the gelatine about the third or 

 fourth day, rendering it somewhat opaque, from which we should gather 

 that the organism is motile ; on plates it forms colonies which are usually 



