516 THE NERVOUS SYSTEM. 



The motor root passes beneath the Gasserian ganglion, and 

 takes no part in its formation. 



Beyond the ganglion the fifth nerve divides into three parts : 

 (1) ophthalmic; (2) superior maxillary; and (3) inferior maxil- 

 lary. 



*(1) Ophthalmic Division. This division, which leaves the 

 cranium by the sphenoidal fissure, is distributed to the tentorium 

 cerebelli, the eyeball, the Schneiderian membrane, the lacrimal 

 gland, and the skin about the forehead and nose ; and also supplies 

 branches to the ciliary ganglion. It contains fibers from the 

 posterior root only ; none from the anterior. 



(2) Superior Maxillary Division. This division of the fifth 

 pair leaves the cranial cavity by the foramen rotundum. It is 

 distributed to the dura mater, the sphenopalatine ganglion 

 (Meckel's), the skin of the temple and cheek, the teeth, the 

 gums, the mucous membrane of the upper jaw and upper lip, the 

 mucous membrane of the lower part of the nasal passages, and 

 the skin of the lower eyelid, side of nose, and upper lip. There 

 are no fibers of the anterior root in this division. 



(3) Inferior Maxillary Division. As has already been stated, 

 there is no anatomic connection between the motor root of the 

 fifth nerve and the Gasserian ganglion. From this ganglion are 

 given off nerve-fibers which join the motor root, together making 

 the inferior maxillary division, which escapes through the foramen 

 ovale. It is distributed to the dura mater, the otic ganglion, the 

 mucous membrane of the cheek and skin, the mucous membrane 

 of the lower lip, the anterior wall of the external auditory meatus, 

 the front of the external ear and the skin of the adjacent temporal 

 region, the submaxillary gland and ganglion, the mucous mem- 

 brane of the mouth and tongue ; to the papillae at the tip, the 

 edges, and anterior two-thirds of the tongue, and to the teeth and 

 gums of the lower jaw. It also supplies the following muscles : 

 Temporal, masseter, pterygoid, mylohyoid, and anterior belly of the 

 digastric. 



Physiologic Properties of the Trigeminus. The trigeminus is 

 the largest of the cranial nerves, and its functions are many and 

 important. It supplies the parts to which it is distributed with 

 the general sensibility they possess. If it is divided, there is 

 complete absence of sensation (anesthesia) of the face on the cor- 

 responding side. So pronounced is this anesthesia that no amount 

 of irritation applied to such ordinarily sensitive parts as the cornea 

 will produce any effect. An animal thus experimented upon 

 seems entirely unconscious of the irritation. Experimenters have 

 gone so far as to exsect the eyeball and apply hot irons to the 

 skin without causing pain to the animal experimented upon. 



Neuralgia of the face, headache, and toothache are all due to 

 some interference with the normal functions of this nerve. It is 



