406 MABEL BISHOP 



gation. The auriculotemporal and inferior alveolar branches 

 are identifiable, however. 



The Ungual branch is of special interest, because in this teras 

 there are two tongues united at their roots, but innerved only 

 from the outer (normal) sides of the two heads (figs. 4, 19). 

 Whether or not these nerves would have given sufficient inner- 

 vation for normal functioning of the tongues had the teras 

 developed to term is impossible to say. The chorda tympani 

 branch of the seventh nerve, which accompanies the lingual 

 nerve from the external pterygoid muscle to the tongue, is well 

 developed (fig. 18). 



VI. Nervus abducens. The superficial origin of the abducens 

 is medial and slightly caudal to that of the fifth nerve. It 

 curves outward around the ventral border of the gasserian 

 ganglion, coursing between the ganglion and the internal carotid 

 artery, the third and fourth nerves. It terminates in the external 

 rectus muscle of the eye (figs. 4, 15). 



VII and VIII. Nervi facialis and acusticus. Embryologically, 

 these two nerves are so closely associated it is convenient to 

 consider them under one heading. The seventh nerve is readily 

 recognized by the geniculate ganglion on its sensory root, which 

 Hes in normal embryonic relation to the auditory capsule and 

 the sensory ganglion of the trigeminus (fig. 15). From its 

 ganghon the facial nerve gives off peripherally the posterior 

 auricular, the mandibular, the inferior alveolar, the superficial 

 petrosal, and the chorda tympani branches — all easily identified 

 by their distribution. Traced brainward from the geniculate 

 ganghon, the nerve is followed with equal ease through the 

 facial canal and is seen to come into normal relation with the 

 eighth nerve (figs. 13, 14, 15). Near the ganglion the nervus 

 intermedins of Wrisberg is recognized lying between the motor 

 root of the seventh and the acoustic ganglion, but a little farther 

 craniad it seems to be lost among the fascicles of the eighth 

 nerve. The motor root of the facial nerve emerges from the 

 ventrolateral margin of the medulla, ventrocaudad of the roots 

 of the trigeminus, and ventromedial of the acoustic, i.e., between 

 the fifth and the eighth nerves (fig. 4) . 



