58 F. W. THYNG 



From the cochlear division short fibers extend ventrally to the 

 cochlear duct (D.c). The central fibers of the ganglion acus- 

 ticum (N.acus.) enter the caudo-ventral wall of the metencephalon 

 slightly dorsal and caudal to the sensory root of the facialis. 



N. glosso-pharyngeus. The motor fibers of the glosso-pharyn- 

 geal nerve (plates 2, 3 and 6) issue from the myelencephalon just 

 ventral to the entering sensory roots. The latter are hidden 

 partially from view in plate 3 by the ductus endolymphaticus 

 (D.end.) and crus commune, but are exposed in plate 2, 



The small ganglion superius (G.sup.) lies at the medial side of 

 the ampulla of the posterior semicircular canal, separated from it 

 by a narrow zone of the developing otic capsule. It extends 

 slightly dorsal to the ampulla, and apparently involves only the 

 more posterior and medial of the fibers of the nerve. 



The ganglion petrosum (G.petros.) is a large ganglion, the 

 caudo-lateral surface of which is closely applied to the trunk and 

 ganglion nodosum of the vagus which somewhat overlap it. The 

 medial surface of this ganglion is in contact with the internal 

 carotid artery and the accompanying sympathetic fibers. From 

 the cephalic part of the ganglion arises the tympanic nerve 

 {N.tym.) which extends cephalad lateral to the internal carotid 

 artery and nearly parallel with it. It passes dorsal to the re- 

 mains of the second pharyngeal pouch and to the auditory (first 

 pharyngeal) pouch, and lateral to the stapedial artery close to 

 its origin. A little cephalad of the stapedial artery it is joined 

 by a slender branch from the great superficial petrosal as de- 

 scribed above (p. 57). The small superficial petrosal, resulting 

 from this communication, I have been able to trace as far as a 

 point near the caudo-ventral border of the semilunar ganglion. 



Beyond the ganglion petrosum the glossophar^mgeal nerve 

 skirts closely around the caudal aspect of the remains of the 

 second pharyngeal pouch and reaches the ganglion nodosum. 

 At the ventral border of the lateral pharyngeal wall it receives a 

 branch (not shown in the figure) from the superior cervical sym- 

 pathetic ganglion. This branch, extending around the medial 

 side of the internal carotid artery, joins the dorsal aspect of the 



