214 TWENTIETH LECTURE. 



tures have sometimes been met with, and sometimes also not 

 found. 



The dental nerves appear to be peculiarly constituted (Boll). 

 We have long been familiar with medullated nerve tubes, 

 0.0067 to 0.0038 mm. in diameter, situated in the parietes of 

 the dental sac. They form below an elongated nerve plexus. 



From the dichotomous separation of these nerve tubes 

 arise innumerable very fine primitive fibrillar. They press 

 through the covering of the odontoblasts (p. 75), reach the 

 inner surface of the dentine, and probably penetrate the den- 

 tinal tubules. The latter have, according to this, a double 

 variety of contents, one part being the filamentous processes 

 of the odontoblasts, and then the remains of these nervous 

 filaments. The sensitiveness of the dentine has also been 

 long known by the dentists. 



