214 MICROSCOPIC ANATOMY OF THE TEETH 



minute spaces which exist between the terminal branches 

 of the dendrons of communicating cells. . This is known as 

 the neuron theory, and has been confirmed by many observa- 

 tions and experiments. 



Although able to show in 1912 (22 a) that neurofibrils enter 



-d 



n 



FIG. 1 29. Human premolar. Nerve cells and their processes in the pulp. 

 d. Dentine ; ' s. separation between pulp and dentine crossed by axon 

 processes and dentinal fibril: n. nerve-end cells; p. pulp. (x800.) 



the dentinal tubes and are distributed to the dentine, it was 

 long before the author was able to establish the correct mode 

 of distribution of the nerves of the pulp. In former prepara- 

 tions he had noticed as a very puzzling fact that the nerve 

 fibres which passed up to the dentine from the deep plexus 

 were very much larger and thicker than those which entered 

 into the plexus beneath the odontoblasts, and attributed this 



