THE DENTAL PULP 223 



from the dentine he could also trace them between these 

 fibrils. From these observations he concluded that the nerve 

 fibres entered the tubes of the dentine. Boll was not 

 successful in actually tracing them into the hard substance, 

 but he appears to have been the first observer who had 

 succeeded in tracing them so far in their course from pulp 

 to dentine. 



Kolliker (1867), speaking of the nerves of the pulp, says : 

 ' As regards their endings, one sees, here and there, loop- 

 like curves of the fibres, but it is beyond doubt that these 

 are not the last endings.' 



Professor Klein, in 1883 (15), says : * Numerous medul- 

 lated nerve fibres, forming plexuses, are met with in the pulp 

 tissue ; on the outer surface of the pulp they become 

 non-medullated fibres, and probably ascend in the dentinal 

 tubes.' 



Several histologists have attempted to account for sensa- 

 tion in the hard substance of the tooth apart from the 

 actual presence of nerves, considering that the soft material 

 occupying the dentinal tubule conducted sensation to the 

 nerves of the pulp. .The principal supporters of this view 

 have, been Hope well Smith and Dr. Aitchison Robertson, 

 although they differ in their views as to the actual anatomical 

 path by which sensation is transmitted. 



Hopewell Smith (11) has long held the view that the 

 function of the odontoblast cell is that of a nerve-end organ, 

 sensation being conveyed through the dentinal fibril, which 

 is a protoplasmic prolongation of this cell. He was able to 

 show, by means of teased-out preparations from the pulp, 

 that the nerve fibres when stained with methylene blue, 

 took on the characteristic varicose appearance, and were 

 seen in great abundance immediately around the odonto- 

 blasts. He was unable to trace fibres into the cells, although 

 they enclosed them in a fine network. 



Hopewell Smith, while allowing the objection that the 

 epiblastic nerve fibres are connected with cells derived from 

 the mesoblast, says : ' Accepting the statement of Schafer 

 (that all nerve fibres and nerve cells are originally derived 

 from the neural or neuro-sensory epiblast) one is led to the 

 conclusion that odontoblasts cannot possibly be, from 



