98 



ZOOLOGY 



SECT. 



two branches, a superficial (V. o. s. and a deep V. o.p) : it is purely 

 sensory, and supplies the skin in the neighbourhood of the mouth 

 and certain parts in the orbit. The maxillary nerve (V. mx.) is 

 also sensory : it supplies the parts in relation with the upper jaw, 

 including the teeth. The mandibular nerve (V. md.) is partly 

 sensory, partly motor : it supplies the muscles of the jaws, the 

 skin and teeth of the lower jaw, and sends off a gustatory nerve 

 or nerve of taste to the epithelium of the tongue. The ophthalmic 

 nerve is connected by a branch with the ciliary ganglion. 



The sixth or abducent (Figs. 734 and 742, VI.) is a small motor 

 nerve, arising from the ventral region of the medulla, and sup- 

 plying the external rectus muscle of the eye. We thus have the 

 remarkable fact that out of ten, or at the most twelve, cerebral 



sj/m 



br. 7 



FIG. 734. Diagram of the cerebral and anterior spinal nerves of a Craniate. I, olfactory 

 nerve ; II, optic ; III, oculomotor ; IV, trochlear ; V. trigeminal ; V. o. s. superficial ophthal- 

 mic branch ; V. o. }>. deep ophthalmic ; VI, abducent ; VII, facial ; VII. /;, hyomandibular 

 branch ; VII. p, palatine branch ; VIII, auditory ; IX, glossopharyngeal ; X, vagus ; X. br. 

 1 5, branchial branches ; X. c, cardiac branch ; X. g, gastric branch ; X. 1, lateral branch ; 

 XI, accessory ; XII, hypoglossal. au. auditory organ; br. 1 7, branchial clefts; cblm. cere- 

 bellum ; c. ffii. ciliary ganglion ; c. It. cerebral hemispheres ; d. dorsal branch of spinal nerve ; 

 d. /. dorsal root ; c. eye ; gn. d. r. ganglion of dorsal root ; m. l>. mid-brain ; mcd. obi. medulla 

 oblongata ; mth. mouth ; na. olfactory sac; o. I. olfactory lobe; pn. b. pineal body ; pn. e. 

 pineal eye ; */>. c. spinal cord ; */,>. 1 3, ventral branches of spinal nerves ; sum. sympathetic 

 nerve ; $1/111. [in. sympathetic ganglion ; v. r. ventral root. 



nerves, three are devoted to the supply of the six small muscles 

 by which the eye-ball is moved, and of those by which the accom- 

 modation of the eye for varying distances is effected. 



The seventh or facial (Fig. 734, VII.) is, like the fifth, a mixed 

 nerve in the lower Craniata, i.e., contains both sensory and motor 

 fibres. It arises from the side of the medulla, a short distance 

 behind the fifth, and is dilated near its origin into & facial ganglion. 

 It has two chief branches, a palatine (VII. p.}, which passes in 

 front of the mandibulo-hyoid gill-cleft, and supplies the mucous 

 membrane of the palate, and a hyomandibular (VII. h.\ which 

 passes behind the same cleft and sends branches to the lower 

 jaw, and to the hyoid arch. In aquatic Vertebrata an ophthalmic 

 branch is given off from the trunk of the nerve, and usually 



