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further evidence in favour of the foregoing views. If a carious tooth, 

 hi which the disease has advanced but slowly, and the carious por- 

 tion is dark in colour and tolerably firm in consistence, be examined, 

 it will be found that the dentinal fibrils have become calcified, and 

 in a favourable section they may be seen projecting from the edge of 

 the specimen, or lying broken in short lengths in the tubes. On 

 removing the diseased part of the tooth in such a case, no pain is 

 experienced until the instrument reaches the healthy dentine. Sup- 

 posing, however, the disease to have been rapid in its progress, the 

 carious tissue will be light in colour, and, as compared with the pre- 

 ceding example, soft in consistence. The removal of the aifected part 

 in this case is frequently attended with considerable pain. Exami- 

 nation will then show that the dentinal fibrils have not been conso- 

 lidated, but may be found here and there extending into the softened 

 tissue without having suffered any appreciable alteration of appear- 

 ance. 



Daily experience shows that a tooth may remain useful for a long 

 time after the pulp, and consequently the dentinal fibrils, have been 

 destroyed/ If, however, a tooth which has been so circumstanced be 

 examined, it will be found that one of two actions has been set up. 

 Either additional cementum will have been developed upon the 

 surface of the fang, or its bulk will have become diminished by 

 absorption. Similar conditions supervene when the crown of a tooth 

 has been lost by caries. 



In old persons we find the teeth are lost without apparent disease 

 in the dental tissues. The teeth become loose and fall out, the roots 

 being in such cases translucent like horn. This condition is the 

 result of consolidation of the dentinal fibrils, and is followed by 

 absorption of the cementum and dentine. Cases may be found in 

 which the whole of the fang has been absorbed, but reduction to 

 two-thirds or half of the normal bulk is very common. 



The concurrence of the foregoing changes in the sensibility of the 

 tooth, with the destruction or consolidation of the dentinal fibrils, 

 will, the author considers, justify the conclusion, that the dentinal 

 fibrils, in a state of integrity, are necessary to the normal condition 

 of dentine. 



