126 



PHYSIOLOGY. 



brain ; and that also result from blows that jar the optic nerve or 

 ganglia. 



The mal-appreciation of colours, like the deficient musical ear, is 

 rather an encephalic defect, than in any way connected with the 

 visual organ itself. 



THE ENCEPHAMC NERVES. 



The only encephalic nerves whose functions have not been alluded 

 to, are ihe fifth ; portio dura of the seventh; and the eighth pairs. 

 The fifth and eighth pairs combine the functions of sensitive and 

 motor nerves. The portio dura is entirely motor. 



The fifth pair presents a remarkable resemblance to the spinal 

 nerves in its mode of origin. It arises by two roots, a larger and a 

 smaller ; the larger is involved in a ganglion, and the two are quite 

 distinct until after the formation of the ganglion. The trunk of the 

 nerve separates into three branches, the opthalmic, the superior- maxil- 

 lary, and the inferior maxillary. 

 Fig. 36.* The first two consist exclusively 



of fibres derived from the poste- 

 rior, or larger root, and ganglion ; 

 the third is composed of fibres 

 from both roots : it is the only 

 portion that is strictly compound, 

 (Fig. 36.) 



The ophthalmic and superior 

 maxillary being composed of 

 fibres from the posterior root, 

 are exclusively sensitive. The 

 inferior maxillary is both motor 

 and sensitive. The ophthalmic 

 and superior maxillary are dis- 

 tributed entirely to sentient sur- 

 faces ; division of them, there- 

 fore, destroys the sensibility of 

 those parts, without impairing the 

 muscular action. The inferior 

 maxillary sends some branches 

 and motor filaments to the mus- 

 cles of mastication ; the others go to the integuments of the lower 

 part of the face, and the mucous membrane of the mouth and tongue, 

 which they supply with general sensibility. Division of these last 

 destroys the general sfensibility in the parts to which they are distri- 



* A view of the distribution of the fifth pair. 6. First branch of the fifth pair or ophthal- 

 mic. 7. Second branch or superior maxillary. 8. Third branch or inferior branch. For 

 other references, see Anatomy. 



