236 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



thalamus. It will be remembered that these fibres of the dorsal columns 

 are physiologically joined with the contra-lateral thalamus and hemisphere. 

 In part, however, the axones from the dorsal nuclei enter the cerebellum by 



the inferior peduncle of the same side, and we shall refer to this when con- 

 sidering the cerebellum. 



Cranial Nerves. — We shall next consider briefly the relations of the sev- 

 eral atfcreiit cranial nerve.-, beginning with the vagus and working cephalad. 



Nervus Vagus\ Tenth Nerve). — The nucleus of termination for the afferent 

 fibres of the tenth nerve (vagus) are shown in Fig. 91. The afferent fibres 

 of this nerve are found to convey impulses which arise in the pharynx, oesoph- 

 agus, stomach, liver, pancreas, spleen, larynx, bronchi, and lungs. Further, 

 this nerve contributes afferent fibres to the nervus laryngeus superior. The 

 location of the nucleus of termination (X. alse cinerse) falls within the area of 

 the mi ml vital. Concerning the axones of the neurones forming the nucleus 

 of termination, it can only he said that they are continued cephalad in the 

 medial lemniscus and the fasciculus longitudinalis medialis. 



Nervus Glossopharyngeus [Ninth Nerve). — The ninth nerve (glossopharyn- 

 geus, Fig. 91) i> represented in the hull) by the tractus solitarius, the fibres 

 of which find their principal nucleus of termination in the cell-group lying 

 ju-t to the medial side of the tract. The neurones of this nucleus send their 

 axones cephalad by way of the medial lemniscus. The afferent fibres of N. 

 glossopharyngeus mediate general sensations for the tonsils and pharynx, the 

 tympanic cavity and Eustachian tube, while by way of the ramus lingualis 

 ir innervates the taste-organs of the posterior part of the tongue and those in 

 the pharynx. In addition to these fibres mediating the sense of taste, patho- 

 logical evidence points to some additional fibres with the same function (not 

 belonging to the ninth nerve) which reach the bulb by way of the fifth nerve 

 and the nervus intermedins. The nuclei of termination for these three nerves 

 are very close to one another in the bulb, and hence the innervation of a 

 special -en-e-organ from three cranial nerves, which, in the first instance, 

 seems anomalous, becomes more intelligible when it is recognized that the 

 nuclei concerned are practically continuous. 



Nervus Intermedius. — In this connection the afferent fibres in the nervus 

 intermedins (of Wrisberg) should be mentioned. These fibres arise from the 

 cell-bodies of the ganglion geniculatum, enter the bulb between the super- 

 ficial origin of the seventh and the vestibular root of the eighth nerve, and, 

 running caudad along the dorso-medial tip of the ascending root of the fifth, 

 finally terminate with the fibres of the glossopharyngeus in the cells of ter- 

 mination found along the tractus solitarius. The longitudinal extension of 

 these fibres of the nervus intermedius in the bulb closely matches that of the 

 nucleu- of the eighth nerve, and at the periphery the fibres from the genicu- 

 late ganglion are distributed, in part at least, with those of the seventh nerve.' 



Nervus Auditorius ( Eighth Nerve). — A. Cochlear Hoot. — The eighth nerve 



1 Van Gehuchten : "Becherches sur la Terminaison centrale des Nerfs sensible peripheri- 

 ques — le Nerf intermediary de Wrisberg." Le N&uraxe, Mars, 1900, t. i. fasc. 1. 



