THE DENTAL TISSUES. 69 



According to Neumann, in old age the fibrils atrophy or 

 become calcined ; some observers have failed to detect them 

 near to the periphery of the dentine, far away from the pulp 

 cavity. But here they would naturally be more minute, 

 and it is more probable that the manipulations had failed 

 to demonstrate them than that they were absent ; for 

 Bodecker has traced them to the very outside of the 

 dentine. 



Dr. Beale has seen prolongations of the nucleus of the cell 

 towards the base of the fibril, though in the example which 

 he figures it does not enter it. 



Dentinal fibrils have been demonstrated in the Reptilia 

 and Amphibia by Santi Sirena and myself; and by myself 

 in the few fish that I have examined with that purpose. 



Of their real nature some doubts are entertained : they 

 are certainly processes of the formative cells of the dentine, 

 and their substance seems identical with that of the proto- 

 plasm of the cell. Nerves, in the ordinary sense of the 

 word, they are not, and have never been supposed to be ; 

 but there are many examples of cellular structures which 

 are connected with the termination of sensory nerve fibres, 

 such as the goblet cells in the olfactory membrane of the 

 frog, and it is quite possible that the odontoblast cells may 

 stand in some such relations to the nerve of the pulp, the 

 termination of which have never been satisfactorily traced. 



Mr. Coleman once suggested that it was possible that 

 the odontoblasts might have some tactile function ; but 

 M. Magitot has recently claimed for them a very definite 

 connection with the nerves of the pulp. According 

 to his observations and figures the nerves of the pulp 

 become continuous with a layer of reticulate cells which lie 

 beneath the odontoblasts ; and these freely communicate 

 with the processes of the odontoblasts, so that there is a 

 very direct chain of communication between the dentinal 

 fibril and the nerves of the pulp. M. Magitot speaks very 



