578 NERVOUS SYSTEM. 



with the properties of other sensory nerves, is nevertheless distinct. It is 

 impossible, however, to expose the roots of the nerves in living animals, be- 

 fore they have received communicating motor filaments, without such muti- 

 lation as would interfere with accurate observations; but in animals just 

 killed, if the roots be exposed and divided, so as to avoid reflex movements, 

 and if care be taken to avoid stimulation of motor filaments from adjacent 

 nerves, it is found that the application of electricity to the peripheral end of 

 the root, from its origin to the ganglion, gives rise to no movements. It may 

 therefore be assumed that the true filaments of origin of the pneumogastrics 

 are exclusively sensory or at least that they have no motor properties. 



Properties and Uses of the Auricular Nerves. There is very little to be 

 said with regard to the auricular nerves after a description of their anatomy. 

 They are sometimes described with the facial and sometimes with the pneu- 

 mogastric. They contain filaments from the facial, the pneumogastric and 

 the glosso-pharyngeal. The sensory filaments of these nerves give sensibility 

 to the upper part of the external auditory meatus and the membrana tym- 

 pani. 



Properties and Uses of the Pharyngeal Nerves. The pharyngeal branches 

 of the pneumogastric are mixed nerves, their motor filaments being derived 

 from the spinal accessory ; and their direct action upon the muscles of deglu- 

 tition belongs to the physiological history of the last-named nerve. As 

 already stated in treating of the spinal accessory, the filaments of communica- 

 tion that go to the pharyngeal branches of the pneumogastric are distributed 

 to the pharyngeal muscles. 



It is impossible to divide all of the pharyngeal filaments in living animals 

 and observe directly how far the general sensibility of the pharynx and the 

 reflex phenomena of deglutition are influenced by this section. As far as 

 one can judge from the distribution of the filaments to the mucous membrane, 

 it would seem that they combine with the pharyngeal filaments of the fifth, 

 and possibly with sensory filaments from the glosso-pharyngeal, in giving 

 general sensibility to these parts. 



In the experiments of Waller and Prevost, upon the reflex phenomena of 

 deglutition, it is shown that the action of the pharyngeal muscles can not be 

 excited by stimulation of the mucous membrane of the supralaryngeal region 

 and the pharynx, after section of the fifth and of the superior laryngeal 

 branches of the pneumogastrics. This would seem to show that yie pharyn- 

 geal branches of the pneumogastrics are of little importance in these reflex 

 phenomena. 



Properties and Uses of the Superior Laryngeal Nerves. The stimulation 

 of these nerves produces intense pain and contraction of the crico-thyroids ; 

 but it has been shown by experiment that the arytenoid muscles, through 

 which the nerves pass, receive no motor filaments. The influence of the 

 nerves upon the muscles resolves itself into the action of the crico-thyroids, 

 which has been treated of fully under the head of phonation. When these 

 muscles are paralyzed, the voice becomes hoarse. The filaments to the in- 

 ferior muscles of the pharynx are few and comparatively unimportant. The 



