136 NERVOUS SYSTEM. 



muscle and the mylo-hyqid, receive their innervation from the motor 

 root of the fifth nerve. Besides this, the tensor palati and tensor 

 tympani muscles are supplied by this nerve through its communi- 

 cation with the otic ganglion of the sympathetic system. A branch 

 to the buccinator muscle is probably not motor, but sensory. Le- 

 sions of the nerves paralyze these muscles. 



What is the distribution of the sensory root ? 



The sensory fibres of the fifth nerve are distributed in all three 

 branches, and supply sensation to the skin of the face and anterior 

 portion of the head, emerging from the bony canals upon the face 

 at the supraorbital, infraorbital, and mental foramina ; it is also 

 supplied to the mucous membrane of the mouth and tongue (by 

 the lingual branch) and to the muscles of the part. 



What results follow division of the sensory root of the fifth nerve ? 

 There is complete anaesthesia of the skin and mucous membranes 

 of the face. 



What is the trophic influence of this nerve -root ? 



It is of very great value. If it be divided, the complete anaes- 

 thesia of the conjunctiva, of the nostrils, and of the lips prevents 

 the reflex self-protection which belongs to the parts, and they be- 

 come injured very easily. Aside from that, the direct influence 

 upon all the parts is great, so that when it is cut off there is a 

 rapid degeneration resulting, which is specially apparent in the 

 mucous membrane of the nose and in the cornea. 



What influence has the sensory branch upon the special senses ? 



(1) Its division causes total anaesthesia to the skin and mucous 

 membrane ; the loss of the sense of touch in the part is of great 

 importance, for the tongue and lips are used much for this. 

 (2) Upon th'e sense of sight it has a very controlling influence, 

 for, as we have seen, the trophic influence is essential to the 

 maintenance of the integrity of the eye. (3) Upon the sense of 

 smell. Here the influence is the same as with the eyes, trophic. 

 The smell is soon lost on account of degeneration of the mucous 

 membrane after division of the fifth nerve. (4) Taste, prob- 

 ably, is not a direct function of the nerve, but if the tactile sensi- 

 bility is gone and the trophic changes are begun, the sense of taste 

 soon disappears in the anterior portion of the tongue. (5) Upon 

 the hearing the effect is more gradual and less distinct. The secre- 



