THE TEETH. 



673 



authors seem to have had an intimation of this idea, since they were inclined 

 to consider the textural changes in carious dentine as vital processes. There 

 can be no doubt that the sensibility, sometimes increasing to actual pain, of 

 the dentine, when deprived of its protecting covering, is a vital action, and 

 that this becomes diminished when the most sensitive, the peripheral portion, 

 is destroyed by an external agent. These facts, however, are by no means 

 sufficient to enable us to draw a conclusion in favor of the reactionary power 

 of dentine in parts which are attacked by caries. In consequence of the 

 decomposition of the secretions, acids are formed which extract the calcareous 

 salts from the hard tissue, and give rise to a disintegration of the affected 

 portions of the latter, in which no inflammatory reaction occurs." 



Tomes* says: " Although dental caries has been investigated and de- 

 scribed by all who have written upon the subject of Dental Surgery, from 

 the earliest period when disorders of the teeth first attracted attention down 

 to the present time, yet it can scarcely be said that the nature of the disease 

 is perfectly understood, for even now two hypotheses prevail. In one the 

 disease is assumed to be no disease whatever, but merely the result of 

 chemical solution of the dental tissues, and therefore dependent both in its 

 origin and its progress on the uncontrolled action of physical and chemical 

 laws. According to the other hypothesis, the fact that teeth are part of a 

 living organism, if not essential to the origin of the mischief, at all events 

 profoundly modifies its progress. . . . Caries is an effect of external causes 

 in which so-called ' vital ' forces play no part." 



The processes concerned in the destruction of the temporary 

 teeth were studied in my laboratory by Frank Abbott, but the 

 result is not yet ready for publication. The bay-like excavations 

 observed in the cement and the dentine are due to a dissolution, 

 first, of the lime-salts, and afterward of the basis-substance, which 

 causes the reappearance of bioplasson in certain pre-formed ter- 

 ritories. The new infiltration of these territories with basis- 

 substance often results, even in the dentine, in a formation of 

 bone-tissue, and it is probable that the same process takes place 

 in the enamel also. How much of the erosions, which are visible 

 in these structures, is due to a growth of granulation tissue into 

 the dental tissues from without, has not yet been positively 

 determined. 



The development of the teeth has for a number of years been 

 studied in my laboratory by C. F. W. Bodecker, and these 

 studies are not yet completed. One of the important facts 

 gained by the researches of Bodecker is, that the views held by 

 former observers, concerning the development of the enamel, 

 is erroneous. It is true that the enamel starts as an epithelial 

 prolongation of the oral cavity, but the epithelia themselves 

 never participate in the formation of enamel. The epithelia 



43 



'System of Dental Surgery," 1873. 



