SEA-FISHERIES LABORATORY. 281 



The single root of the ixth (r. ix.) leaves the medulla 

 much below and somewhat behind the root of the lateralis. 

 It is situated quite by itself, and distinct from any other 

 root. It passes almost straight backwards above and 

 slightly to the inner side of the posterior division of the 

 acusticus, and becomes related to the R. acust. ampullae 

 posterioris as above described. It then courses almost 

 straight outwards and downwards, first between the 

 sacculus and utriculus, and afterwards between the 

 sacculus and the skull. It now bends forwards and down- 

 wards, passes through its foramen (represented by a ring 

 in the chart), and enters the large ganglion (g. ix.) lying 

 just outside the skull. 



Before entering the ganglion, and just after leaving 

 the foramen, the root gives off above a motor branch. 

 This passes forwards over the top of the ganglion, and 

 enters the R. post-trematicus, thus accounting for most 

 of the motor fibres of the glossopharyngeus. 



The peculiar course of the root first backwards and 

 then forwards is due to the position of the ear. That is 

 to say it passes straight backwards until it can escape 

 outwards through the fissure between the sacculus and the 

 utriculus behind. 



The nerve arising from the ganglion is very flattened 

 and ribbon-like, and soon splits into two large nerves — an 

 upper R. post-trematicus and a lower Jacobson's 

 anastomosis (Jac. anast.). The latter passes forwards, 

 gives off a motor branch below, the fibres of which have 

 previously traversed the ganglion to reach it, and finally 

 anastomoses with the post-trematicus vii., which see for 

 its subsequent course. The relations of the sympathetic 

 to the glossopharyngeus are described with the former 

 system. 



R. post-trematicus (post. ix.). — Courses forwards 



