I 



MESENCEPHALIC ROOT 183 



Its cephalic pole is continuous with the two large sensory, com- 

 ponents of the nervns trigeminus, the N. ophthalmicus and N. 

 maxillaris (fig. 3, Oph. and Max.), both of which enter the orbit 

 through the orbital fissure and the foramen rotundum, respec- 

 tively. The N. mandibularis complex leaves the ventrolateral 

 surface of the ganglion midway between the two poles, and from 

 the caudal pole of the gangUon the trigeminal roots pass to the 

 brain stem. 



From figure 3 the mandibular nerve will be seen to have sepa- 

 rated into three branches at its appearance from the semilunar 

 ganglion. The most caudal of these is the nervus auriculotem- 

 poralis (Aur.T.), which is entirely sensory, pursues a general 

 caudolateral course, at first caudal to the mandible, then pene- 

 trating the temporal muscle, innervates the skin immediately in 

 front of the external auditory meatus. Stimulating this nerve 

 with a weak mduction current produced no contraction of the 

 temporal muscle. Also serial sections from experiment no. 65, 

 in which the trigeminal motor nucleus had been largely de- 

 stroyed, demonstrated the absence of motor fibers in this nerve. 

 The main division of the N. mandibularis (fig. 3, Man.) assumes 

 a general ventral course median to the mandible. In the region 

 of the angle of the mandible it divides into its three characteristic 

 branches, the N, lingualis (Lin.) to the tongue, the N. alveo- 

 laris inferior {Inf. A.) to the mandibular canal, and the N. mylo- 

 hyoideus (Myloh.) to the mylohyoid and digastric muscles. 

 Stimulation of the mandibular nerve with a weak induction 

 current produced a contraction of the digastric muscle. Also 

 serial section from experiment no. 65 demonstrated degenerated 

 motor fibers going to this nerve. The third division of the 

 mandibular trunk, the N. masticatorius (fig. 3, Mast.), after 

 leaving the semilunar ganglion lateral to the main mandibular 

 nerve, passes in front of the mandible, to pursue a general lateral, 

 ventral, and cephaUc course. With the exception of the buccal 

 branch, it is composed entirely of trigeminal motor fibers.^ The N. 



2 In this description a nerve consisting purely of motor fibers means the entire 

 absence of general cutaneous or somatic sensory fibers. Muscle sense is not 

 considered. 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 30, NO. 2 



