152 NERVOUS SYSTEM. 



the superficial muscles of the face, leaving the deep muscles, 

 or the muscles of mastication, to be supplied by the motor 

 root of the fifth. In addition, it supplies in part the platys- 

 ma myoides. "VYe have already seen that the buccal branch 

 of the small root of the fifth is not distributed to the 

 buccinator, but that this muscle is supplied exclusively by 

 branches from the facial. 1 



Properties and Function of the Facial Nerve. It has 

 long been recognized that the facial is the motor nerve of 

 the superficial muscles of the face, and that its division pro- 

 duces paralysis of motion and no marked effects upon sensa- 

 tion. It is evident, also, from the numerous communica- 

 tions of the facial with the fifth, that it probably contains in 

 its course sensitive fibres. Indeed, all who have operated 

 upon this nerve have found that it is slightly sensitive after 

 it has emerged from the cranial cavity. It is a question, 

 however, of great importance to determine, whether or not 

 the facial be endowed with sensibility by virtue of its own 

 fibres of origin. The main root is evidently from the motor 

 tract, resembles the anterior roots of the spinal nerves, and 

 is distributed to muscles ; but this is joined by the interme- 

 diary nerve of "Wrisberg, which presents a small enlarge- 

 ment, undoubtedly containing nerve-cells, somewhat analo- 

 gous to the ganglia upon the posterior roots of the spinal 

 nerves. 



If the facial possess any sensibility at its root, it is but 

 slight. In the early experiments of Sir Charles Bell, irrita- 

 tion of the facial exposed in an ass apparently produced no 

 pain, 2 but the roots were not exposed in the cranial cavity. 

 Magendie, on the other hand, in repeating these observa- 

 tions, found the nerve distinctly sensitive. 3 Longet, and 



1 See page 142. 



2 BELL, On the Nerves, etc. Philosophical Transactions, London, 1821, Part 

 I., pp. 413, 418. 



8 MAGENDIE, Journal de physiologic, Paris, 1822, tome ii., p. 67, note. 



