526 MANUAL OF PHYSIOLOGY. 



nerve, being somewhat analogous to it in origin, function, and 

 the fact that there is a large ganglion on it within the cranium. 



The distribution and peripheral connections of this nerve are 

 somewhat complicated, and should be carefully studied when the 

 manifold functions of its branches are being considered. The 

 various impulses conveyed by the trifacial nerves may be thus 

 enumerated : 



i. EFFERENT FIBRES. 



1. Motor. To the muscles of (1) mastication, viz., temporal 

 masseters, both pterygoids, mylo-hyoid, and the anterior part of 

 the digastrica ; (2) to the tensor muscle of the soft palate ; and 

 (3) to the tensor tympani ; (4) in some animals (rabbit) nerve 

 filaments also pass to the dilator muscle of the iris, reaching the 

 eyeball by the ciliary ganglion. 



2. Secretory. The efferent impulses which stimulate the cells 

 of the lachrymal gland to increased action pass along the branches 

 of the ophthalmic division of this nerve. 



3. Vasomotor. The nerves governing the muscles of the blood 

 vessels of the eye, of the lower jaw, and of the mucous membrane 

 of the cheeks and gums. 



4. Trophic. On account of the impairment of nutrition of the 

 eye and the mucous membrane of the mouth, which occurs after 

 injury of the fifth nerve, it is said to carry fibres which preside 

 over the trophic arrangements of these parts. 



ii. AFFERENT FIBRES. 



1. Sensory. All three divisions of the trifacial nerve may be 

 said to terminate in cutaneous nerves, by which the ordinary 

 sensory impulses are carried from (1) the entire skin of the 

 face and the anterior surface of the external ear ; (2) from the 

 external auditory meatus ; (3) from the teeth and the periosteum 

 of the jaws, etc.; (4) from the mucous membrane lining the 

 cheeks, the floor of the mouth, and the anterior part of the 

 tongue ; (5) from the lining membrane of the nasal cavity ; (6) 

 from the conjunctiva, the ball of the eye, and the orbit generally ; 

 (7) and from the dura mater, including the tentorium. 



2. Excito-motor. Some of the fibres which have just been 



