NERVES OF MAMMALIA. 155 



olfactory : ( the other nerves of this part, derived from other 

 origins, only conveying common sensation.' ' It is upon this 

 principle the fifth pair of nerves may be supposed to supply 

 the eye and nose in common with other parts, and upon the same 

 principle it is more than probable, that every nerve so affected as 

 to communicate sensation, in whatever part of the nerve the im- 

 pression is made, always gives the same sensation as if affected 

 at the common seat of sensation of that particular nerve,' ib. 

 p. 190. 1 



The nerve which is homologous with the e ramus opercularis 

 sen facialis,' and some other branches of the non-ganglionic part 

 of the ' fifth,' in Fishes (vol. i. p. 303), is more distinct in its 

 origin, at least its apparent one, in Mammals, and is reckoned in 

 Anthropotomy as a separate cerebral nerve, under the name of 

 6 facial,' or as a part, e portio dura,' of the ( seventh pair,' with 

 which it has less real relation or connection than with the fifth. 

 It is essentially the complementary proportion of the motory or 

 non-ganglionic part of that great myelonal nerve of the head. 

 In fig. 131 is shown the point, behind the olivary tract, where 

 the facial, 16, diverges from the smaller portion of the motor 

 division accompanying the sensory division of the trigeminal : 

 its angle of divergence is wide, and its place of emergence is 

 behind the c pons,' close to that of the acoustic nerve, fig. 128, y. 

 It enters, therewith, the internal auditory foramen, leaves the 

 acoustic to enter its own canal in the petrosal, called ( aqueduct 

 of Fallopius ' in Anthropotomy, passes downward behind the 

 tympanic bone (as in Birds), and emerges by a foramen called 

 ( stylo-mastoid.' The facial nerve supplies the muscles of the 

 mouth, nose, eyelids, ear-conchs, and the cutaneous muscles of 

 the head and beginning of the neck. In the Porpoise, the facial 

 nerve, on quitting the petrosal, gives small branches to the 

 cutaneous muscular layer of the ear-opening and parts behind, 

 communicating; with filaments of the cervical nerves : a branch 



o 



ramifies on the mylohyoid muscle. From the trunk of the facial 

 a slender nerve passes to above the mandibular joint, then bends 

 forward, enters into, and receives a filament from, a sympathetic 

 plexus, and quits it to join the third division of the fifth : this 

 answers to the f chorda tympani.' The trunk of the facial is, 



1 One of the observations and experiments on which Hunter founded this conclu- 

 sion, is given, in Latin, by Sir C. Bell, in his original Essay, LXIV", p. 11 (1811). So, 

 also, Sir Charles writes: ' The key to the natural system of the nerves will be found 

 in the simple proposit'on, that each filament or tract of nervous matter has its pecu- 

 l ; ar endowments independently of the others which are bound up along with it, and 

 that it continues to have the same endowment throughout its whole length.' LXV", p. 70. 



