FUNCTIONS OF THE PAR VAGUM. 315 



cles. Much controversy has taken place on the question, whether this nerve is to 

 be regarded as ministering, partly or exclusively, to the sense of Taste ; and 

 many high authorities have ranged themselves on each side. The question 

 involves that of the function of the Lingual branch of the Fifth pair; and it is 

 partly to be decided by the anatomical relations of the two nerves respectively. 

 The glosso-pharyngeal is principally distributed on the mucous surface of the 

 fauces, and on the back of the tongue. According to Valentin, it sends a 

 branch forwards, on either side, somewhat beneath the lateral margin, which 

 supplies the edges and inferior surface of the tip of the tongue, and inosculates 

 with the Lingual branch of the Fifth pair. On the other hand, the upper sur- 

 face of the front of the tongue is supplied by this lingual branch. The experi- 

 ments of Dr. Alcock, whose conclusions are borne out by Dr. J. Reid, de- 

 cidedly support the conclusion, that the gustative sensibility of this part of 

 the tongue is "due to the latter nerve, being evidently impaired by division of 

 it. Moreover, cases are by no means rare, in which the gustative sensibility 

 of the anterior part of the tongue has been destroyed, with its tactual sensi- 

 bility ; when there was no reason to suppose that any other than the Fifth 

 pair of nerves was involved.* On the other hand, it is equally certain, that 

 the sense of taste is not destroyed by section of the Lingual nerve on each 

 side; and it seems also well ascertained, that it is impaired by section of the 

 Glosso-pharyngeal nerve. Considering how nearly allied is the sense of 

 Taste to that of Touch, and bearing in mind the respective distribution of 

 these two nerves, it does not seem difficult to arrive at the conclusion, that both 

 nerves are concerned in this function ; but there seems good reason to believe 

 the Glosso-pharyngeal to be exclusively that through which the impressions 

 made by disagreeable substances taken into the mouth are propagated to the 

 Medulla Oblongata, so as to produce nausea, and to excite efforts to vomit. 



408. Tlie functions of the Par Vagum at its roots have lately been made 

 the subject of particular examination by various experimenters; some of 

 whom (for instance, Bischoff, Valentin, Longet, and Morgan ti), have concluded 

 that it there possesses no motor power, but is entirely a sensory, or rather, an 

 afferent nerve. According to these, if the roots be carefully separated from 

 those of the Glosso-Pharyngeal, and (which is a matter of some difficulty) 

 from those of the spinal Accessory nerve, and be then irritated, no movements 

 of the organs supplied by it can be observed ; whilst, if the roots be irritated 

 when in connection with the nervous centres, muscular contractions, evidently 

 of a reflex character, result from the irritation ; and strong evidences of their 

 sensibility are also given. It has been further asserted that, when the roots 

 of the Spinal Accessory nerve are irritated, no indications of sensation are 

 given ; but that the muscular parts supplied by the Par Vagum, as well as by 

 its own trunk, are made to contract, even when the roots are separated from 

 the nervous centres; so that these roots must be regarded as the channel of 

 the motor influence, transmitted to them from the Medulla Oblongata. When 

 the Par Vagum swells into the jugular ganglion, an interchange of fibres takes 

 place between it and the Spinal Accessory; and it seems clear that the pha- 

 ryngeal branches, which are among the most decidedly motor of all those 

 given off from the Pneumogastric, may in great part be traced backwards into 

 the Spinal Accessory. These statements confirm the idea of Arnold and 

 Scarpa, that the Par Vagum and Spinal Accessory are together analogous to 

 a spinal nerve, the former answering to the posterior roots, and the latter to 

 the anterior. But, on the other hand, an equally numerous and trustworthy 

 set of experimenters (among whom may be mentioned J. Reid, Miiller, Volk- 

 mann, and Stilling) are opposed to this opinion ; maintaining that the Par Va- 

 gum has motor roots of its own, and that the Spinal Accessory possesses sen- 



* Romberg, in Mailer's Archiv., 1838, Heft m. 



