368 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



this muscle to the parasphenoid and that bone. Here it detaches a 

 superficial branch for the mucous membrane over the entoptergyoid, 

 and then penetrates the fleshy anterior part of the adductor a/rcus 

 palatini where it forms two branches. The more medial of these is 

 stronger and more superficial in the substance of the muscle, but 

 both end in the premaxillary teeth and the mucous membrane of the 

 lips and anterior part of the roof of the mouth. 



Ramus ad. m. adductorem mandibulce. — This strong branch is 

 derived from the supero-lateral strand immediately on its emergence 

 from the skull, soon gains the dorsal aspect of the retractor muscle 

 of the maxillary barblet which it supplies, and then distributes itself 

 in the fleshy mass of the adductor mandibulce after giving off a super- 

 ficial branch. This (Fig. 3, PI. IV.) contains fibres for the levator 

 arcus palatini and dilatator operculi, and also furnishes a cutaneous 

 branch which communicates with a similar branch of the facial 

 crossing the surface of the adductor mandibulce. 



The mode in which the Br. maxillaris and mandibularis are formed 

 by the redistribution of the fibres of the supero-lateral and infero- 

 medial strands is shown in Fig. 1 , PI. IV. Each nerve contains ele- 

 ments from both strands. 



Ramus maxillaris. — This branch is considerably smaller than the 

 R. mandibularis, owing, no doubt, in part to the reduction and con- 

 version of the superior maxillary bones. It is accompanied by the 

 ramus buccalis as far as the hinder end of the palate bone where it 

 divides into medial and lateral branches. The former turns over the 

 dorsal surface of the palate bone, and ends in the lateral premaxillary 

 teeth and the neighbouring skin, while the latter, after detaching 

 some cutaneous branches, passes between the split tendon of the- 

 retractor muscle of the maxillary barblet and divides into two 

 branches for the anterior and posterior aspects of the barblet. 



Ramus mandibularis. — The two constituent strands may remain 

 separate while the nerve gains the dorsal aspect of the retractor 

 muscle of the maxillary barblet. Here it gives off a branch which 

 accompanies the tendon of that muscle to the posterior aspect of the 

 barblet, and then divides into the external and internal branches. 

 The former, R. externus is given off at the anterior border of the 

 insertion of the adductor mandibulce, and passes along the external 

 edge of the lower lip communicating with a fine cutaneous branch 

 of the facial which accompanies it at a somewhat lower level. The 



