NoRRlS, Nerves of Amphiuma. 53 1 



It is doubtful whether this should be considered as a source dis- 

 tinct from the preceding. (3) According to Kingsbury (1895a) 

 and to OsBORN (1888) there occurs in Necturus a tract of fibers 

 from the so-called trigeminal nidus in the roof of the mid-brain 

 that passes in part into the spinal V tract near the exit of the fifth 

 nerve. I find in Amphiuma a similar tract of large fibers from 

 the mid-brain passing into close proximity to the spinal V tract 

 and apparently giving ofi^ fibers to the latter near the motor root 

 of the fifth nerve, but the fibers so given off are few in number, the 

 greater number passing apparently posteriorly mesal to the spinal 

 V tract, as many do in Necturus. (4) From motor fibers in one 

 or two rootlets that come from a nidus of cells lying in the floor of 

 the medulla. 



KiNGSLEY speaks of the fact that the fifth nerve leaves the 

 brain as three roots: dorsal and ventral small roots and a median 

 large one. The small dorsal root is made up of fibers that com- 

 pose (2) above. In this region the spinal V tract is reinforced by 

 numerous fibers from the adjoining cinerea. This small dorsal 

 root appears to be merely some of these fibers that delay the union 

 until after emergence from the brain. The small ventral root 

 is the motor component. As it leaves the brain the fifth nerve 

 contains only motor and general cutaneous fibers. 



b. The ramus mandibularis V. — The fibers of the fifth nerve 

 leave the gasserian ganglion in three groups. There is first given 

 off the r. mandibularis, composed of motor and general cutaneous 

 fibers, innervating the temporal, masseter, pterygoid, interman- 

 dibular (mylohyoid anterior), retractor bulbi and levator bulbi 

 muscles, and supplying the skin of the lower jaw and the side of 

 the head (in part). The r. mandibularis passes out of the cranium 

 through a foramen common to it and the "dorsal VII." It 

 emerges at the posterior dorsal border of the pterygoid muscle, 

 at first enters the masseter muscle, then passes anteriorly, ventrally 

 and laterally between the pterygoid and masseter muscles, finally 

 out through the masseter. On emerging from the skull it gives 

 ofi^ a number of small twigs to the pterygoid and masseter muscles. 

 As the main trunk of the nerve is passing through the foramen 

 there is given off a large branch which rising rapidly between the 

 pterygoid muscle and the internal portion of the masseter and 

 giving off branches to the anterior part of the pterygoid muscle 

 passes around to the dorsal side of the cranium and runs pos- 



