464 THE NERVOUS SYSTEM. 



to perceive when it is reduced to the proper consistency for swallowing, 

 and to detect any remnants left among folds or crevices of the mucous 

 membrane. 



The lingual nerve is also endowed with the special sensibility of 

 taste. This function is difficult to investigate in animals, owing to the 

 uncertainty of its indications, and the difficulty of isolating separate 

 regions of the cavity of the mouth. Experiments upon man, which are 

 made with comparative facility, have been performed by Guyot, Ver- 

 niere, Duges, and Longet in such a manner as to leave no doubt that 

 the sense of taste is highly developed in those portions of the tongue 

 exclusively supplied by the lingual nerve. They consist mainly in 

 applying to different parts of the mucous membrane a pellet of lint, 

 moistened with a solution of some substance, like quinine or colocynth, 

 possessing a distinct taste without irritating qualities. In this way it is 

 ascertained that the point, edges, and upper surface of the tongue, through- 

 out its anterior two-thirds, is capable of perceiving sensations of taste, 

 without aid from other parts of the mucous membrane. According 

 to the experiments of Bernard and Longet on animals, division of the 

 lingual nerve destroys the faculty of taste as well as that of general 

 sensibility in the corresponding parts of the tongue ; and similar obser- 

 vations are quoted by Henle, after section of this nerve in man. 



Muscular Branches of the Fifth Pair. These branches, which are 

 all given off from the inferior maxillary division of the nerve, are dis- 

 tributed to the temporal, the masseter, and the external and internal 

 pterygoid muscles, as well as the mylohyoid muscle and the anterior 

 belly of the digastric. They are all therefore concerned in the move- 

 ments of mastication. The most powerful of the muscles to which they 

 are distributed, namely, the temporal and the masseter, act by bring- 

 ing the teeth of the lower jaw forcibly in contact with those of the 

 upper. The action of the pterygoid muscles produces a lateral grind- 

 ing movement, by which the trituration of the food is accomplished ; 

 and finally those supplied by the mylohyoid branch act by opening the 

 jaws, to allow a repetition of the former motions. In different animals 

 these movements vary in relative importance. In the carnivora, the 

 closure of the jaws preponderates over the rest, enabling the animal 

 to seize and retain his prey. In the herbivora, the lateral grinding 

 movements are more important for comminuting the seeds, grains, vege- 

 table fibres and other hard substances upon which they feed. In man, 

 both movements exist in a nearly equal degree. 



Anastomotic Branches of the Fifth Pair. Although the superior, 

 middle, and inferior regions of the face are respectively supplied, in 

 general, by the three great divisions of this nerve, there is yet more 

 or less communication between adjacent branches, so that each region 

 receives fibres from different sources. Thus the infraorbital nerve, 

 which sends filaments to the lower eyelid, inosculates with a branch 

 of the ophthalmic division. The integument of the nose is supplied 

 by the nasal branches of the ophthalmic division, and also by those 



