THE GLOSSO-PHARYNGEAL NERVE. 



1 26 1 



and from the motor portion proceed the fibres supplying the musculature of the 

 oesophagus, stomach, respiratory tract and heart. The nucleus obliquely under- 

 lies the floor of the fourth ventricle, extending from the stri« acusticae above 

 into the closed part of the medulla below. It shows on the ventricular floor as a 

 narrow depressed area, the ala cinerea, close and lateral to the hypoglossal trigone 

 (Fig. 949). Examined in cross-sections (Fig. 928), the nucleus appears prismatic 

 in outline and consists of subgroups of cells, the larger median group correspond- 

 ing, in general, to the dorsal motor nucleus. In addition to supplying the above 

 mentioned involuntary muscle, the dorsal nucleus gives origin to secretory 

 fibres distributed to the salivary and other glands by way of the seventh and 

 ninth nerves. 



The nucleus ambiguus consists of a slender column of large multipolar 

 cells, within the substantia reticularis grisea, between the dorsal accessory olivary 

 nucleus and the substantia 



gelatinosa (Fig. 927). The nu- 1^10.1073. 



cleus extends from the level of 

 the cochlear nerve to about the 

 decussation of the median fillet. 

 The upper part of the nucleus 

 ambiguus, is appropriated by the 

 ninth nerve and is entirely de- 

 voted to the supply of the stylo- 

 pharyngeus muscle. On the 

 contrary, the vagus, in con- 

 junction with the accessory por- 

 tion of the eleventh nerve, is 

 more extensively concerned with 

 the nucleus ambiguus, since from 

 this source are derived the motor 

 fibres supplying the constrictors 

 of the pharynx and the intrinsic 

 muscles of the larynx. It is 

 probable that the axones to these 

 muscles arise from the caudal or 

 accessory portion of the nucleus. 



The Sensory Nuclei. — 

 The terminal masses of gray 

 matter, the sensory nuclei, in- 

 clude the sensory part of the 

 dorsal nucleus, above described, 

 and the gray matter accompany- ... . . . , , 



,1 v/ + 4- T^U ^^i^ Diagram showing connections of root-fibres of glosso-pharyngeal 



mg tne solitary tract. llie sen- and pneumogastrlc nerves and of sensory fibres of facial ; sensory 



<5nrv Hnr<;al nnrlens ic i-nm fibres are black, motor ones red ; ^'/Z, geniculate ganglion; /A', 



SOry aorsai nucleus is com- X, ganglia of ninth and tenth nerves ; I? A^, dorsal nucleus -J^-^: 



posed of neurones similar to those fasciculus soluanus, accompanied by column of gray matter; JVA, 



r J . ,1 , • 1 r nucleus ambiguus; ^<:K, accessory vagus (bulbar portion of A'/); 



found in the posterior horn of mj^, median fiiiet. 

 thes pinal cord. Around these 



cells the axones of the afferent fibres end, chiefly as visceral contributions from 

 the vagus, but in small part also from the ninth nerve. The fasciculus solitarius 

 is devoted especially to carrying the stimuli for taste and, therefore, is appropri- 

 ated chiefly by the glosso-pharyngeus, only a small part of the tract serving the 

 vagus. The solitary fasciculus {tractus solitarius) appears (Fig. 928) as a round 

 isolated strand, beginning at the superior limit of the medulla and continuing 

 downward through its entire length. Closely applied to the lateral side of the 

 bundle, an investing mass of gray matter forms the true nucleus of reception 

 (nucleus TRACTUS soLiTARii). The highest fibres entering the bundle soon end, 

 around the cells of the nucleus, while those entering at lower levels end, in turn 



about other cells. 



« 



Central and Cortical Connections of the Motor Part of the Glosso-Pharyngeal Nerve. — 



The motor fibres of the glosso-pharyngeal nerve are the axones of the motor neurones situated 



