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On the Distribution of the Nerves of the Dented Pulp. 



By J. Howard Mummery. 



(Communicated by Prof. J. Symington, F.R.S. Received November 6, 1911, — 

 Read February 1, 1912.) 



(Abstract.) 



The mode of innervation of the dentine of the human tooth has long been 

 a matter of controversy ; while clinical evidence is strongly in favour of a nerve 

 supply to this tissue, the difficulties meb with in tracing nerve fibres in such 

 a difficult substance to examine, as the dentine, has been a very considerable 

 hindrance to the investigation. It has been very difficult to account for 

 the passage of such very acute sensation from the periphery of the dentine 

 in the absence of nerve fibres in that situation, and I have long felt, 

 with others, that sensation in the tooth would be found to be conducted by 

 nerve fibres, as in other tissues of the body. As long ago as 1891 I made 

 preparations which appeared to show that nerve fibres from the pulp entered 

 the dentine, but, by the iron and tannin impregnation process I then employed, 

 could not satisfactorily demonstrate it. 



During the last year I have, I think, with several methods of preparation, 

 been successful in making it fully evident that the dentine is richly supplied 

 with nerves from the pulp, which do not terminate, as has been hitherto 

 generally supposed, at the inner margin of the dentine, but enter the tubules 

 of that tissue and traverse them to their peripheral terminations at the enamel 

 and cementum margins. 



The bundles of medullated fibres which enter the tooth at the apical 

 foramen traverse the pulp in more or less parallel lines, running in most cases 

 in company with the blood-vessels. They send off numerous side branches, 

 which at the periphery of the pulp lose their medullary sheath, the axis 

 cylinders spreading out into a mass of neurofibrils which enter into a more or 

 less dense plexus beneath the odontoblast layer of cells. From this plexus, 

 known as the plexus of Raschkow, fine neurofibrils pass between and around 

 the odontoblasts, enclosing them in a fine meshwork, and enter into a narrow 

 plexus at the inner margin of the dentine. This has usually been described 

 as the mode of termination of the nerve fibres of the pulp, but fibres can be 

 seen arising from this plexus, which might be better termed the " marginal 

 plexus," and passing into the dentinal tubes. 



These neurofibrils pass into the dentine in great abundance and seem to be 

 equally distributed in the coronal portion and considerably below the neck of 



