212 MICROSCOPIC ANATOMY OF THE TEETH 



muscle this nerve divides into two branches, a small anterior 

 branch chiefly consisting of motor fibres and distributed to 

 the temporal, masseter, and external pterygoid muscles, 

 and a buccal branch, which is its only sensory portion. 

 The posterior, the larger branch of the inferior maxillary 

 nerve, consists chiefly of sensory fibres and divides into the 

 auric ulo-temporal, lingual, and inferior dental nerves. 



The inferior dental nerve passes beneath the external 

 pterygoid muscle to the outer side of the lingual nerve and 

 enters the inferior dental canal, whence it supplies branches 

 to the molar and premolar teeth and the canine. At the 

 mental foramen it issues from the canal and divides into the 

 incisor branch distributed to the lower incisors, and the 

 mental branch passing to the face in the mental region. 



Several bundles of medullated fibres enter the pulp in 

 company with the blood-vessels, and maintain an intimate 

 association with them throughout their course. The main 

 bundles divide and subdivide and give off numerous branches 

 to the periphery of the pulp, but the larger nerve trunks 

 pursue a more or less direct course to the crown portion of 

 the pulp, where they lose their medullary sheath and the 

 axis cylinders spread out to their ultimate distribution. 

 Many preparations show that in company with these 

 medullated fibres are other nerve fibres which do not stain 

 with osmic acid, and probably are derived from the sym- 

 pathetic system and possess trophic functions. The passage 

 of the larger medullated bundles to the crown of the pulp 

 before dividing is accounted for by the much larger area 

 of dentine to be supplied at the crown portion of the tooth 

 than at that of its lateral margins. These larger bundles 

 of nerve fibres can often be seen at a definite point in the 

 pulp to lose their medullary sheath and neurolemma, and 

 give rise to a brush or fan-shaped expansion of delicate 

 fibres (fig. 128). These are the fibres of the axis cylinder of 

 the nerve, and the neurofibrils constituting them pass into 

 a plexus beneath the odontoblast region the plexus of 

 Raschkow. 



At the lower margin of the odontoblast layer, as shown 

 by the author in a recent paper, 1 the delicate nerve fibres 

 1 Communicated to the Royal Society in May 1918. 



