3o8 Journal of Comparative Neurology. 



of the mandible a branch of the dorsal division enters the 

 alveolar canal of the dentary bone and apparently sup- 

 plies its teeth. 



Returning now to the coarse-fibred ventral division 

 (165), it follows parallel with the dorsal division the inner 

 face of the mandible and at about 150 gives off ventrally 

 about one-fourth of its fibres, comprising some very 

 coarse ones and some of the medium size {inan. VII. 11). 

 At 130 these fibres pass through a foramen in the dentary 

 bone into the mandibular canal, where they supply the 

 fourth mandibular canal organ. 



At the level of that organ (120) the main nerve is joined 

 by a branch of about the same size which is derived from 

 the r, mandibularis V {V-VII. 2) and passes ventrad 

 between the articular bone and Meckel's cartilage to the 

 dorsal surface of the r. mandibularis VII. It is composed 

 of fine, medium and very coarse fibres, the latter occu- 

 pying about one-third of the area of the cross-section. 

 Though the elements from the VII and V nerves are 

 from this point on intimately united and bound up in the 

 same sheath, yet in good preparations it is possible to fol- 

 low them independently for a considerable distance, for 

 they are separated by a delicate connective tissue septum. 

 All the coarser and some of the fine fibres from the tri- 

 geminus gradually swing around mesally from the dorsal 

 to the ventral side of the mixed trunk, while the remainder 

 of the trigeminal fibres retain the dorsal position. A con- 

 nective tissue septum appears between these two portions 

 of the trigeminal element and finally (100) the ventral por- 

 tion separates from the trunk. While it is impossible to be 

 certain that no fibres from the facialis enter this branch, 

 the appearances are against it and it is certain that most 

 of its fibres are derived from the trigeminal element. 



