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the pulp-cavity. The dentine will, when cut, break up into small 

 fragments, and from the edges of these the fibrils may be seen 

 extending. Sometimes a small portion of the pulp will be found 

 adherent, in which case the fibrils may be seen to extend from that 

 tissue into the dentine. The fibrils may be shown in a more striking 

 manner by decalcifying a section, and then, when it is placed upon a 

 slide, tearing the specimen across the direction of the tubes. By 

 this manipulation, the fibrils will be dragged out from one fragment, 

 and will be seen projecting from the edge of the other. 



The fibrils, when isolated and examined with a high power, with- 

 out the presence of a reagent, show some indications of tubularity, 

 but not with sufficient distinctness to enable the author to determine 

 whether they are tubes or solid bodies. Their appearance is very 

 like that of the ultimate fibrils of spinal nerves, and they possess a 

 character in common with these, in the presence of minute globules 

 of dense transparent matter exuded from the broken ends, and some- 

 times from the surface of the fibril. It is not easy to determine in 

 what manner the fibrils commence in the pulp. In some prepa- 

 rations they appear to be connected with cells situated a short 

 distance within the pulp, in others they may be traced to a greater 

 depth, where they are lost in the tissue of the pulp, and may possibly 

 be connected with the nerves, which in this part are very abundant. 

 But in the absence of exact knowledge as to the manner in which the 

 dentinal fibrils are related to the elements of the pulp, the author 

 considers that there is sufficient evidence to warrant the conclusion 

 that they are organs of sensation, the distribution of which through 

 the substance of the dentine endows that tissue with its sensibility. 



This conclusion is borne out by the occurrence of the following 

 conditions. If a fragment of enamel be broken from the surface of 

 the dentine, the exposed portion of the latter tissue is highly sen- 

 sitive to the contact of foreign bodies ; but if the force producing the 

 injury be sufficient to rupture the nerves and vessels where they 

 enter the root of the tooth, the dentine loses its capability of feeling 

 pain. Again, if the dentine be exposed by the gradual wearing away 

 of the enamel by mastication, the surface evinces no sensibility, a 

 circumstance accounted for by the fact that the dentinal tubes have 

 become consolidated, either at the surface exposed, or at some point 

 between the surface and the pulp-cavity. Diseased teeth furnish 



