224 MICROSCOPIC ANATOMY OF THE 'TEETH 



the developmental point of view, ganglion cells in which 

 sensory, or tactile, or trophic influences arise de novo. 

 But it is no argument against the idea that they serve as 

 sensation transmitters.' In the last edition of his Histology, 

 1919, this author says : 'As the result of his researches the 

 author has the strongest conviction that these fibres ter- 

 minate in a basketwork of varicose fibres embracing and 

 often closely attached to the cell walls of the individual 

 odontoblasts.' 



In the absence of evidence of the passage of nerves into 

 the dentine we can understand this to be a possible, although 

 an improbable, explanation of the mode in which the 

 dentine transmits sensory impulses, but we do not think 

 there has ever been any proof that such mode of transmission 

 occurs in the mammalian tooth. Weil of Munich held 

 a similar view and says : ' As things stand at present 

 nothing lies in the way of the theory that each delicate 

 fibril of the basal layer of the membrana eboris is a means 

 of connexion between the nervous system and the odonto- 

 blasts, and that the latter formations may be regarded 

 as nerve endings,' but he goes on to say that it is only an 

 hypothesis that time may prove to be true, and must limit 

 himself to saying that nerve fibres or groups of such cannot 

 be found beyond the cortical layer of the pulp. 



Magitot in 1 879 ( 1 8) described certain ramified cells beneath 

 the odontoblasts which he said were in continuity by their 

 processes with the nerve fibres on one hand and the basal 

 prolongations of the odontoblasts on the other, thus ' forming 

 a direct chain of sensation '. The existence of such an 

 arrangement has, however, never been corroborated by other 

 observers. 



In 1891 Aitchison Robertson contributed a paper to 

 the Royal Society of Edinburgh in which he asserted his 

 conviction ' that the central processes of the odontoblasts 

 become continuous with nerve fibres ' (27). 



' The central process seems to become the axis cylinder 

 of a nerve fibre which gradually acquires a primitive sheath 

 in which the medullary substance slowly accumulates till an 

 ordinary medullated nerve fibre results.' He would thus 

 look upon the odontoblasts and dentinal fibrils as the 



