THE INFRA-ORBITAL TRUNK. 183 



along the ventro-lateral side of the latter for a consider- 

 able distance. Its first branch, the 12th of the infra- 

 orbital trunk (440), is of coarse fibres, which innervate 

 the mesal portion of the m. adductor mandibulse cephalad 

 of this point. The main nerve now passes farther laterally 

 in the floor of the orbit, separating somewhat from the 

 dorsal division. Its coarse fibres, which we shall see are 

 all of the motor type, are mingled among the fine ones 

 and do not segregate themselves as lateralis fibres 

 usually do. 



The 13th branch leaves the r. mandibularis V at 375. 

 This, too, is of coarse fibres and supplies the lateral por- 

 tion of the m. adductor mandibulae. At about 300 the r, 

 mandibularis V turns ventrally, passing between two por- 

 tions of the adductor mandibulae and finally running for- 

 ward along the outer face of the ventral edge of the 

 quadrate near its cephalic end. The r. mandibularis VII 

 lies in a corresponding position on the inner face of the 

 same bone a little farther ventrad. 



While in this position the r. mandibularis V gives off 

 another branch (the 14th mfra-orbital, V-VII, i) com- 

 posed of fine and medium fibres. Beyond the cephalic 

 end of the quadrate this branch turns outward and under 

 the skin over the articular bone and between and behind 

 the open ends of the infra-orbital and mandibular canals 

 it divides into numerous ramuli. Several of the smaller 

 ramuli supply the skin adjacent to the end of the infra- 

 orbital canal and that about the open space between the 

 mandibular and opercular canals (it will be remembered 

 that the infra-orbital canal disappears for a part of its 

 course and closes in again at this point), and a larger 

 ramulus runs caudad under the skin along the ventral 

 edge of the m. adductor mandibulae. This is the com- 



