THE DENTAL TISSUES. 107 



brana eboris, and taking a direction parallel to that of the 

 dentinal fibrils in such numbers that he infers that they 

 have been pulled out from the canals of the dentine. Still, 

 whatever may be the probabilities of the case, he has not 

 seen a nerve fibre definitely to pass into a dentinal canal, 

 nor has any other observer been more fortunate. 



Boll's observations have not however been fully confirmed 

 by any subsequent 'worker in the field, nor have they been 

 definitely controverted until Magitot recently stated that he 

 had fully satisfied himself that the nerves become continuous 

 with the branched somewhat stellate cells which form a layer 

 beneath the odontoblasts, and through the medium of these 

 cells, with the odontoblasts themselves. (See Fig. 32.) 



If this view of their relation to the nerves be correct the 

 sensitiveness of the dentine would be fully accounted for 

 without the necessity for the supposition that actual nerve 

 fibres enter it, for the dentinal fibrils would be in a 

 measure themselves prolongations of the nerves. 



It has already been mentioned that the pulp undergoes 

 alterations in advanced age, its diminution in size by its 

 progressive calcification and the addition thus made to the 

 walls of the pulp cavity being the most conspicuous change 

 which occurs. In pulps which have undergone a little 

 further degeneration, the odontoblast layer becomes atro- 

 phied ; fibrillar connective tissue becomes more abundant, 

 oiiicidently with the diminution in the quantity of the cel- 

 lular elements. Finally, the capillary system becomes 

 obliterated by the occurrence of thrombosis in the larger 

 vessels, the nerves undergo fatty degeneration, and the pulp 

 becomes reduced to a shrivelled, unvascular, insensitive 

 mass. These changes may go on without leading to actual 

 putrefactive decomposition of the pulp, and are hence not 

 attended by aveolar abscess ; but a tooth in which the pulp 

 has undergone senile atrophy is seldom fast in its socket. 



The pulps of the teeth of some animals become eventually 



