326 THE SOLIDS. 



that the condition of vitality of the teeth and of the states of 

 the saliva were to be considered merely as predisposing causes 

 to the affection. 



This idea acquires some confirmation from an examination 

 of the carious matter of a tooth ; in it vast quantities of minute 

 threads or filaments, possibly tliose of a fungus, are invariably 

 to be discerned, as well as numberless dark granules and irre- 

 gular masses bearing in some cases the aspect of true cells. 



The question may be asked, are these threads, granules, 

 and cell-like masses any thing more than the decomposing 

 elements of the dentine, in which tissue it is that the chief 

 ravages of the decay occur ? The answer is, possibly not ; 

 but the surprising numbers of these filaments and the testi- 

 mony of Mr. Tomes are opposed to the idea that they are the 

 remains of the tubes of the dentine. Mr. Tomes thus writes 

 in his tenth Lecture in reference to the tubes of the dentine : 

 "A transverse section of carious dentine, rendered soft like 

 cartilage from the loss of its lime, presents a cribriform ap- 

 pearance. The tubuli seem enlarged and rather irregular, 

 quite unlike the figure they present in healthy dentine : this 

 would indicate that the solvent enters and acts upon the 

 parietes of the tubes previous to affecting the intertubular 

 tissue, and that the parietes of the tubes are therefore the 

 first to disappear. I feel quite certain that in the cases I 

 have examined, and they are numerous, the parietes of the 

 tubuli, so distinguishable in healthy dentine, have almost, if 

 not wholly, disappeared with the removal of the lime." 



Nature of Tartar on the Teeth. 



Tartar of the teeth consists of phosphate of lime mixed up 

 with the mucus of the mouth and epithelial scales : it con- 

 tains also occasionally animalcules and vegetable growths, 

 which find in the animal matter of the tartar a convenient 

 nidus for their development. The accumulation of tartar 

 around the necks of the teeth results from an opposite condi- 

 tion of the saliva to that to which chemists ascribe dental 

 caries, viz. an alkaline state of it. 



