Mr. Tomes on Fibrils of soft tissue in the Dentinal Tubes. 471 



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 

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

 in 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 affected 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 



