THE CRANIAL OR ENCEPHALIC NERVES. 729 



Motor roots. Several anatomists and physiologists consider these as a 

 portion of the accessory nerve of Willis, and give them the name of internal 

 or bulbous root of the spinal nerve. They are situated a little behind the pre- 

 ceding, and emanate from the respiratory tract ; consequently they are not 

 so elevated as the whole of the sensitive fibres. They are separated from 

 the sensitive roots by a comparatively large vein, and are distinguished from 

 them by their anastomotic tendency. Becoming longer as they are more 

 posterior, and frequently anastomosing with each other, the filaments 

 forming these motor roots converge, and gain the posterior foramen lacerum ; 

 this they pass through by one or two special openings to join the jugular 

 ganglion, beneath and behind which we find them applied. A certain 

 number of the most posterior of these filaments lie beside the medullary 

 root of the spinal nerve ; but they are soon detached to pass with the 

 others to the jugular ganglion. 



Jugular or Ehrenritters ganglion. Elongated from before to behind, 

 and flattened on both sides, the jugular ganglion is embedded in the 

 cartilaginous substance that fills the foramen lacerum. When it has been 

 macerated for some time in dilute nitric acid, it may be resolved into two 

 portions : one corresponding to the sensitive, the other to the motor roots. 

 Some white nervous filaments appear to pass to its surface without becoming 

 confounded with it. It is in relation, in front, with the ganglion of An- 

 dersch ; behind, it crosses somewhat obliquely the medullary root of the 

 spinal nerve. 



The jugular ganglion is also in relation with the spinal, glosso-pharyn- 

 geal, and facial nerve. It communicates with the external root of the spinal 

 nerve by the few radicular filaments indicated above. With the glosso- 

 iharyngeal it is connected by: 1, An afferent filament coming from the 

 lighest roots of the ninth pair, and which meets it at its antero-internal 

 angle ; 2, By an efferent branch it sends to the ganglion of Andersch. 

 Lastly, it is united to the facial by a branch we have named the anasto- 

 mosing branch extending from the pneumogastric to the facial nerve. 



This anastomotic branch, on leaving the jugular ganglion, is somewhat 

 considerable in volume, and it has appeared to us that, at times, among its 

 radicles there were some in direct continuity with the sensitive roots of the 

 pneumogastric nerve. This branch is directed forward, above the ganglion 

 of Andersch, crosses Jacobson's branch, traverses the tuberous portion of 

 the temporal bone, and arrives in the aqueduct of Fallopius ; here it meets 

 the facial nerve, at the point where the latter gives off the chorda tympani. 

 A small number of its fibres then lie beside the nerve of the seventh pair 

 in ascending towards the origin of that nerve, where, in our opinion, they 

 constitute a large portion of the great petrous nerve that which has at 

 its origin the geniculated ganglion. Other fibres descend, on the contrary, 

 in following the proper fibres of the facial nerve, and are lost among these ; 

 but the largest number cross that nerve and continue their course in the 

 substance of the temporal muscle, to be chiefly distributed to the membrane 

 lining the internal auditory canal. 



Course and Relations. Beyond the jugular ganglion, the trunk of the 

 pneumogastric remains intimately allied with the spinal accessory for about 

 8-10ths of an inch ; at this point we have been unable to find the gan- 

 gliform plexus described in Man, though, according to M. Bernard, it exists in 

 the Eabbit. The two nerves then separate to allow the great hypoglossal nerve 

 to pass between them : after which the pneumogastric nerve descends alone 

 behind the guttural pouch, in proximity to the superior cervical ganglion. 



