218 MICROSCOPIC ANATOMY OF THE TEETH 



of cells (figs. 132 and 133). Small enlargements are seen 

 upon the nerve fibres distributed to the odontoblasts, but 

 these definite enlargements are not seen upon the axon 

 processes, which only exhibit the irregular beading character- 

 istic of neurofibrils. 



Huber.(12), Guido Fischer (6), and others, looked upon 

 these enlargements as constituting the end bodies of the 

 nerve fibres of the pulp. They are very abundantly seen in 

 fish and reptiles, as shown by Retzius (26). 



It is these fibres with the nodes or enlargements which 

 the author first described as forming the marginal plexus 

 from which the processes to the dentinal tubes arose. 



FIG. 133. Nerve-end cells in the pulp. ( x 1,000.) 



What was formerly described, however, as the marginal 

 plexus is evidently a portion of the network of fine nerve 

 fibres which envelop the odontoblasts and reach up to the 

 surface of the dentine, this network being derived as described 

 above from the dendrons of the ' end cells '. 



The fibres distributed to the odontoblasts form no con- 

 nexions with them, but closely invest and surround 

 them. The passage of the axon fibres into the dentinal 

 tube is very clearly demonstrated, and can be traced in 

 suitably stained preparations as a winding black fibril 

 within the tube. Nodes or enlargements are often seen upon 

 the fibrils within the tubes, and here and there very delicate 

 branches are given off from these nodes to the finer branches 

 of the dentinal tubes (fig. 135). In fig. 136 are seen the nerve 



