THE FIFTH CRANIAL NERVE. 525 



nal 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 con- 

 junctiva, 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 enu- 

 merated as carrying ordinary sensory impressions have special 

 powers of exciting coordinated reflex motions. Thus the sensory 

 fibres from the conjunctiva and its neighborhood are the afferent 

 channels in the common reflex acts of winking and closing the 

 eyelids ; and the fibres from the nasal mucous membrane com- 

 monly excite the complexly coordinated involuntary act of 

 sneezing. 



3. Exdto-seeretory. In the same way, as in the case of reflex 

 motion, secretion is reflexly excited by the fibres which carry 

 afferent impulses to the medulla from the anterior part of the 

 tongue when the latter is strongly stimulated, and thus excite 

 activity of the salivary secretion ; and severe stimulation of the 

 mucous membrane of the nose or of the eye causes impulses to 

 pass to the secretory centre of the lachrymal glands, which are 

 frequently thus reflexly excited. 



Very intense stimulation of almost any of the afferent nerves 

 may excite these reflex phenomena. Thus the most stoic person 

 will experience active secretions of saliva and lachrymal fluid, 

 as well as spasmodic closure of the lids during the extraction of 

 a tooth. Even the bold use of a blunt razor will cause the tears 

 to flow down the cheeks by sending excito-secretory impulses 

 along the branches of the inferior and superior maxillary divi- 

 sion of this nerve. 



4. Tactile impulses are appreciated by the anterior part of the 

 tongue with remarkable delicacy, and are conveyed by the lingual 

 branch of the fifth nerve ; and most of the cutaneous fibres are 

 also capable of receiving tactile stimulation. 



5. Taste. The tastes that are appreciated by the anterior part 

 and the edges of the tongue are carried by fibres which lie in the 

 peripheral branches of this nerve. These, however, probably 



