560 THE CRANIAL NERVES. 



were in the descent of the heart from the neck to the thorax. The recuiTcnt 

 direction may therefore be accepted as evidence of the development of those 

 nerves before the occun-ence of that descent. The passage of one recurrent 

 laryngeal nerve round the subclavian ai-tery, and of the other round the aorta, 

 arises from the originally symmetrical disposition in which the innominate and 

 subcla\aan ai-teries on the right side and the arch of the aorta on the left are 

 derived from corresponding arches. The supply of the back of the stomach by 

 the right pneumo- gastric nerve, and of the front by the left nerve, is connected 

 with the originally symmetrical condition of the alimentaiy canal, and the 

 turning over of the stomach on its right side in its subsequent growth. 



Branches. — Some of its branches serve to connect the pneumo- 

 gastric with other nerves, and others are distributed to the muscular 

 substance or the mucous lining of the organs which the nerve supplies. 

 The principal connecting branches of this nerve are derived from the 

 ganglia. In the different stages of its course branches are supplied to 

 various organs as follows. In the jugular foramen, a branch is given to 

 the ear ; in the neck, branches are furnished successively to the pharynx, 

 the larynx, and the heart ; and in the thorax, additional branches are 

 distributed to the heart, as well as to the lungs and the oesophagus. 

 Terminal branches in the abdomen are distributed to the stomach, 

 liver, and other organs. 



Connecting- branches and auricular branch. — Connections hcfn'eni the vpper 

 fjanfilion of the raf/ti.s nerve and the xpinal aeeex.sorij. fflosxo-jihari/nf/eal and .fi/inpa- 

 thetic rierves. — The connection with the spinal accessory is effected by one or two 

 filaments. The filament to the petrous ganglion of the glosso-pharj-ngeal is 

 directed transversely : it is not always present. The communication with the 

 sympathetic is established by means of the ascending branch of the upper cei-vical 

 ganglion. 



The (niriet'Je/rhre/nrh is continued to the outer ear. Arising from the ganglion 

 of the root, this branch is joined by a filament from the glosso-pharj-ngeal nerve, 

 and then turns backwards along the outer boundary of the jugular foramen to 

 an opening near the styloid process. Next, it traverses the substance of the 

 temporal bone, crosses the aqueduct of Fallopius about t«-o lines from the lower 

 end. and. reaching the surface between the mastoid process and the external 

 auditory meatus, is distributed to the integument of the back of the ear. On 

 the surface it joins with a twig from the posterior auricular branch of the facial 

 nerves. 



Connections of the second r/ an r/U on with the h>/pofilossal , s)/m2>athetic, and spinal 

 nerves. — This ganglion is connected by filaments with the ti-unk of the hypo- 

 glossal, with the upper cervical ganglion of the sympathetic, and with the loop 

 formed between the first two cervical nerves. 



Pharyngeal branch. — The pharyngeal branch arises from the upper 

 part of the ganglion of the trunk" of the nerve. In its progress in- 

 wards to the pharynx this nerve crosses in some cases over, in others 

 under, the internal carotid artery ; and it divides into branches, which, 

 conjointly with others derived from the glosso-pharyngeal, the superior 

 lai-yngeal, and the sympathetic nerves, form a plexus [pharyngeal) be- 

 hind the middle constrictor of the pharynx. From the plexus branches 

 are given to the muscular structure, and to the mucous membrane of the 

 pharynx. As the pharyngeal nerve crosses the carotid artery, it joins 

 filaments which the glosso-pharyngeal distributes on the same vessel. — 

 There is sometimes a second pharyngeal branch. 



Superior pharyngeal branch. — This nerve springs from tlie middle 

 of the ganglion of the trunk of the pneumo-gastric nerve. It is directed 



