534: HANDBOOK OF PHYSIOLOGY. 



facial nerve lose their power through paralysis of that nerve. The last 

 instance proves best, that though the buccinator muscle gives passage to, 

 and receives some filaments from, a buccal branch of the inferior divi- 

 sion of the fifth nerve, yet it derives its motor power from the facial, for 

 it is paralyzed together with the other muscles that are supplied by the 

 facial, but retains its power when the other muscles of mastication are 

 paralyzed. Whether, however, the branch of the fifth nerve which is 

 supplied to the buccinator muscle is entirely sensory, or in part motor 

 also, must remain for the present doubtful. From the fact that this 

 muscle, besides its other functions, acts in concert or harmony with the 

 muscles of mastication, in keeping the food between the teeth, it might 

 be supposed from analogy, that it would have a motor branch from the 

 same nerve that supplies them. There can be no doubt, however, that 

 the so-called buccal branch of the fifth is, in the main, sensory; although 

 it is not quite certain that it does not give a few motor filaments to the 

 buccinator muscle. 



(b.) Sensory Functions. Through the branches of the greater or 

 ganglionic portion of the fifth nerve, all the anterior and antero-lateral 

 parts of the face and head, with the exception of the skin of the parotid 

 region (which derives branches from the cervical spinal nerves), acquire 

 common sensibility; and among these parts may be included the organs 

 of the special sense, from which common sensations are conveyed 

 through the fifth nerve, and their special sensations through their sev- 

 eral nerves of special sense. The muscles, also, of the face and lower 

 jaw acquire muscular sensibility, through the filaments of the ganglionic 

 portion of the fifth nerve distributed to them with their proper motor 

 nerves. The sensory function of the branches of the greater division of 

 the fifth nerve is proved, by all the usual evidences, such as their dis- 

 tribution in parts that are sensitive and not capable of muscular con- 

 traction, the exceeding sensibility of some of these parts, their loss of 

 sensation when the nerve is paralyzed or divided, the pain without con- 

 vulsions produced by morbid or experimental irritation of the trunk or 

 branches of the nerve, and the analogy of this portion of the fifth to the 

 posterior root of the spinal nerve. 



Other Functions. In relation to muscular movements, the branches 

 of the greater or ganglionic portion of the fifth nerve exercise a manifold 

 influence on the movements of the muscles of the head and face, and 

 other parts in which they are distributed. They do so, in the first place 

 (a), by providing the muscles themselves with that sensibility without 

 which the mind, being unconscious of their position and state, cannot 

 voluntarily exercise them. It is, probably, for conferring this sensi- 

 bility on the muscles, that the branches of the fifth nerve communicate 

 so frequently with those of the facial and hypoglossal, and the nerves of 

 the muscles of the eye; and it is because of the loss of this sensibility 



