THE TRIGEMINUS. 533 



functions are therefore seriously interfered with by injury or destruc- 

 tion of the sensitive filaments supplying the tongue. 



The lingual nerve is also endowed with the special sensibility of 

 taste. This function is a difficult one to investigate upon the lower 

 animals, owing to the uncertainty of its external indications and the 

 difficulty of isolating, for the purposes of observation, separate re- 

 gions of the cavity of the mouth. Experiments upon man, however, 

 which are made with comparative facility, have been performed by 

 Guyot, Verniere, 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 which are supplied exclusively by the lingual nerve. These 

 experiments consist mainly in applying to different parts of the mucous 

 membrane, in the cavity of the mouth, a small globule 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 superior surface of the tongue, throughout 

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

 without aid from other parts of the buccal mucous membrane. Accord- 

 ing 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 the human 

 subject. 



Muscular Branches of the Fifth Pair. These branches, as enume- 

 rated above, are given off from the inferior maxillary division, for the 

 most part a short distance below its exit from the skull, and are dis- 

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

 pterygoid muscles ; while the mylohyoid branch, which separates from 

 the trunk somewhat farther down, supplies the muscle of the same 

 name as well as the anterior belly of the digastric. All these nerves 

 are, therefore, concerned in the movements of mastication. The most 

 powerful of the muscles to which they are distributed, namely, the 

 temporal and the masseter, act by bringing the teeth of the lower jaw 

 forcibly in contact with those of the upper. The contraction of the two 

 pterygoid muscles produces a lateral grinding movement, by which the 

 trituration of the food is accomplished ; and finally those supplied by 

 the mylohyoid branch facilitate the partial separation of the jaws, to 

 allow a repetition of the former motions. In different species of 

 animals these movements vary in their relative importance. In the 

 carnivora, it is the closure of the jaws which preponderates over the 

 rest, enabling the animal to seize and tear his prey, by means of the 

 pointed canine and sharped-edged molar teeth. In the herbivora, on 

 the other hand, the lateral grinding movements are more important for 

 the complete comminution of the seeds, grains, or other hard vegetable 

 tissues upon which they feed. In man, both movements coexist in a 

 nearly equal degree. 



The movements of mastication are accordingly paralyzed by section 



