THE FIFTH CRANIAL NERVE. 527 



enumerated 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 mem- 

 brane commonly excite the complexly coordinated involuntary 

 act of sneezing. 



3. Excito-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 division 

 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 

 belong chiefly, if not altogether, to the chorda tympani, and 

 leave this lingual branch of the fifth to join the seventh nerve 

 on their way to the trunk of the glosso-pharyngeal. 



There are four ganglia in close relation to the branches of the 

 fifth nerve which have certain points of similarity, and may, 

 therefore, be considered together, although their different positions 



