THE NERVOUS SYSTEM 1497 



pharvTigeal and vagus nerves, but in unequal proportions. Only 

 a few glosso-pharyngeal afferent fibres go to the dorsal vago-glosso- 

 pharyngeal nucleus, whereas most of the vagal afferent fibres pass 

 to that nucleus. In the case of the nucleus of the fasciculus solitarius 

 it is the reverse. 



Efferent or Motor Fibres. — ^These fibres arise within the medulla 

 oblongata as the axons of most of the cells of the ventral vago- 

 glosso-pharyngeal nucleus or nucleus ambiguus, which has been 

 described in connection with the glosso-phar\-ngeal nerve. The 

 fibres pass dorsalwards to the more superficially placed dorsal vago- 

 glosso-pharyngeal nucleus. They then alter their course and pass 

 ventralwards and outwards, and associate themselves with the 

 afferent or sensory vagal fibres. 



The ventral vago-glosso-pharA.'ngeal nucleus or nucleus ambiguus, 

 which is a motor nucleus, is shared in common by the efferent or 

 motor fibres of the glosso-pharvTigeal and vagus nerves, especially 

 the latter. 



The funiculi of the pneumogastric or vagus nerve appear in the 

 dcrso-lateral sulcus of the medulla oblongata, between the olivary 

 and restiform bodies, and immediately below the funiculi of the 

 glosso-phar^Tigeal nerve. 



Distribution. — The vagus ner\'e has a very extensive distribution 

 on either side, of which the following is a summar\' : 



Motor Distribution. — (i) The muscles of the soft palate (except 

 the tensor palati) ; (2) the constrictor muscles of the phar\Tix ; (3) the 

 intrinsic muscles of the lar\Tix; (4) the muscular tissue of the 

 oesophagus and stomach; and {5) the muscular tissue of \a) the 

 trachea, {h) the bronchi, and (c) the bronchial tubes. 



Sensory Distribution. — (i) The phar^-nx, oesophagus, and stomach ; 

 (2) the lar\Tix, trachea, and bronchial tubes to their terminal rami- 

 fications ; and (3) the skin on the inner surface of the pinna, as weU 

 as of the lower and back part of the external auditory meatus. 



Cardiac Fibres. — ^The cardiac fibres of the nerve are inhibitory 

 (efferent) and depressor (afierent). 



The most important connection of the vagus nerve is that which 

 is established with the bulbar or accessory portion of the spinal 

 accessory nerve. 



Glosso-pharyngeal and Vagal Nuclei. — ^These two nerves, as 

 stated, consist of afferent or sensory and efferent or motor fibres. 

 The afferent fibres of both ner\-es share in common two terminal 

 nuclei — namely, the dorsal vago-glosso-pharyngeal nucleus and the 

 nucleus of the fasciculus solitarius. Most of the glosso-pharyngeal 

 afferent fibres terminate in the nucleus of the fasciculus solitarius, 

 and most of the vagal afferent fibres terminate in the dorsal vago- 

 glosso-phar^-ngeal nucleus. According to the description which has 

 been given of the dorsal vago-glosso-pharyngeal nucleus, it is a 

 nucleus of termination, or sensory nucleus. According to certain 

 authorities, however, it is a mixed nucleus — ^that is to say, it is both 

 a nucleus of termination, or sensory nucleus, and a nucleus of origin, 



