316 ROBERT J. TERRY 



twig to the posterior ampulla (the two together may be regarded 

 as a ramus medius), and continues as the ramulus basilaris. In 

 addition to the ramulus sa^cculi, described by Retzius ('84), a 

 small twig to the sacculus coming from the anterior ramus was 

 observed. 



The vagus, together with the glossopharyngeus and acces- 

 sorius, form a bundle which occupies a position in the fossa occi- 

 pito-canalicularis close to the lateral occipital arch and consid- 

 erably posterior to the pars canalicularis of the otic capsule (figs. 

 1, 2, 19). The vagus hes medialward of the vena jugularis with 

 the glossopharyngeus anterior and the accessorius posterior to 

 it. These relations are maintained in passing through the jugu- 

 lar foramen, excepting that the accessorius becomes incorpor- 

 ated wdth the vagus. The jugular ganghon is found upon the 

 roots of the vagus as it lies in the fossa occipito-canalicularis 

 and therefore above the jugular foramen. Some distance out- 

 side the cranium the ganglion nodosum appears. 



The ganglion superius of the N. glossopharyngeus (figs. 1, 2, 

 19 to 23) is situated partly in the recessus occipito-canalicularis, 

 and partly upon the roots of the nerve as they lie in the cranial 

 cavity above the recess. The ganglion petrosum, much larger, 

 is located on the nerve below the jugular foramen and above the 

 level of the ganghon nodosum of the vagus. The tympanic 

 nerve arises from the upper end of the ganglion petrosum and 

 proceeds in the direction of the foramen cochleae. This nerve 

 runs in the thick mesenchyma between the medial epithelial wall 

 of the first pharyngeal pouch and the foramen cochleae. After 

 much branching, it reaches the ventrolateral surface of the pos- 

 terior cochlear prominence where it enters a plexus of nerves, 

 derived in part from the sympathetic around the internal carotid 

 artery. 



Blood vessels in the otic region 



A great blood sinus runs upon the inner surface of the cranial 

 wall in the sulcus which circumscribes the pars canalicularis. 

 This, a forerunner of the sinus transversus system, becomes con- 

 tinuous at the fossa occipito-canalicularis with the vena jugularis 



