PAR VAGUM. 



891 



extent with several of the other cerebro-spinal 

 nerves, as the spinal accessory, the glosso- 

 pharyngeal, the hypo-glossal, the portio dura, 

 the two superior cervical, and sometimes with 

 some of the lower cervicals. The vagi are 

 very extensively ramified upon the internal 

 tegumentary membrane, as the mucous mem- 

 brane of the pharynx, larynx, oesophagus, sto- 

 mach, trachea, and lungs, and send only one 

 small branch, viz. the ramus auricularis, to 

 the external tegumentary membrane. Many 

 of its branches are distributed upon the mus- 

 cular fibres surrounding the upper part of the 

 digestive and respiratory tubes. 



Physiology of the nervus vagus. From the 

 distribution of this nerve in so many of the 

 most important organs in the body which it is 

 impossible to insulate, or prevent their mutual 

 actions and reactions upon each other, and 

 from its numerous and intimate connections 

 with several other nerves, investigations into its 

 physiology are beset with unusual difficulties. 

 As, however, its lesions are attended by the 

 most serious derangements of the respiratory 

 and digestive organs, and as a knowledge of 

 its functions bears in a prominent manner upon 

 many interesting questions both in special and 

 general physiology, it has naturally attracted 

 the frequent attention of the physiologist, and 

 has been made the subject of numerous experi- 

 mental investigations. 



Do the roots of the vagus contain any motor 

 filaments? No one can for a moment doubt 

 that the trunk of the vagus, in its course down 

 the neck, does contain motor filaments, but 

 there is every reason to believe that it derives 

 at least the greater part of these from the spinal 

 accessory. From the resemblance of the vagus 

 and spinal accessory as they lie in the foramen 

 lacerum posterius to the anterior and posterior 

 roots of a spinal nerve, the vagus with its supe- 

 rior ganglion corresponding to the posterior, 

 and the spinal accessory to the anterior root, 

 many anatomists and physiologists have of late 

 maintained that the roots of the vagus, like the 

 posterior roots of the spinal nerve, contain no 

 motiferous filaments. It is scarcely necessary 

 to add, that the junction of the internal branch 

 of the accessory and the vagus immediately 

 beyond the superior ganglion of the latter, in- 

 creases still further this resemblance between 

 these and a spinal nerve. This opinion has 

 been maintained on anatomical considerations 

 alone, by Arnold, Scarpa, and Bendz,* and 

 has been further strengthened by the experi- 

 ments of Bischoff, f Valentin,]: and Longet. 



* Tractatus de Connexu inter Nervum Vagura 

 et Accessoriiim Willisii, Haunioe, 1836. According 

 to M'uller, this idea of the resemblance of the ana- 

 tomical arrangement of the vagus and accessory to 

 a spinal nerve had previously suggested itself to 

 Gorres in his Exposition der Physiologic, 1809. 



f Nervi Accessor!) Willisii Anat. et Phys. 1832. 

 Bischoff, however, has more lately satisfied himself 

 by experiment that the root of the vagus does con- 

 tain motor filaments. 



$ De Functionibus Nerv. Cereb. et Nerv. Sym- 

 path. Caput xi. Bernae, 1839. 



Recb.ercb.es Experimentales sur les Functions 

 des Nerfs, des Muscles du Larynx, &c. p. 31, Paris, 



It is on the other hand maintained, that this 

 opinion is too exclusive, and that, though there 

 can be no doubt of the greater part of the fila- 

 ments of the roots of the vagus being incident 

 and sensiferous, yet they do contain some mo- 

 tiferous filaments. We have seen that, proba- 

 bly both in man and in some of the other 

 mammalia, a few of the filaments of the vagus 

 do not pass through its superior ganglion, and 

 consequently the anatomical argument is not 

 so conclusive as it at first appears to be. An 

 examination of the experimental proof adduced 

 in favour of these two opinions shews that the 

 former is chiefly founded upon negative, and 

 the latter upon positive evidence. Miiller* 

 saw muscular movements of the pharynx follow 

 excitation of the roots of the vagus within the 

 cranium ; but from having neglected some pre- 

 cautions in the performance of the experiment, 

 he himself is not disposed to attach to it much 

 weight. I have related some experiments in 

 which I observed muscular movements in the 

 pharynx, larynx, and oesophagus, from irritation 

 of the vagus within the cranium, on the dog 

 immediately after death.f Volkmann has per- 

 formed similar experiments upon calves, sheep, 

 goats, and cats, and perceived muscular con- 

 tractions in the levator palati, azygos uvulae, 

 the superior and inferior constrictor muscles of 

 the pharynx, the palato-pharyngeus, and crico- 

 thyroid.J The experiments of Stilling, Wag- 

 ner,|| Van Kempen,^[ Ilein,** and Bernardft 

 are also all in favour of the opinion that the 

 root of the vagus contains motor filaments. 



1841, and Anatomie et Physiologie du Systeme 

 Nerveux, &c. torn. ii. p. 262. Paris, 1842. 



* Elements of Physiology, translated by Baly, 

 pp. 703-4. Second edition. 



t Edinburgh Medical and Surgical Journal, 1838. 



j Muller's Archives, p. 493, for 1840. Volk- 

 mann expressly states that these muscular contrac- 

 tions were also observed on irritating the vagus 

 within the cranium in the calf, though in that ani- 

 mal all the filaments of the vagus appeared to him 

 to pass through its superior ganglion. 



Stilling states that he saw movements of the 

 pharynx, the glottis, and the stomach in two cats, 

 on exciting the roots of the vagus within the cra- 

 nium. Vide Bischoff's Bericht iiber die Fort- 

 schritte der Physiologie in Jahre 1842, in Muller's 

 Archives for 1843. Heft vi. p. 154. 



|| Lehrbuch der Physiologic. Dritte Abtheilung, 

 S.329. Leipzig, 1842. 



If Van Kempen observed contractions of the con- 

 strictors of the pharynx, the palato-glossus, the 

 oesophagus, and the interior muscles of the larynx. 

 Essai Experimental sur la Nature fonctionelle du 

 Nerf-pneumogastrique, Louvain, 1842. Vide also 

 Bischoff's Bericht, c. supra cit. pp. 154-5. Bischoff 

 states (p. 155) that he himself observed movements 

 of the soft palate, in which the contractions of the 

 levator palati muscle were very decided, on the 

 irritation of the roots both of the vagus and of the 

 accessory. 



** Hein observed contractions in the elevator pa- 

 lati, azygos uvulas, and palato-pharyngeus, but in 

 the last muscle less frequently than in the two 

 former, on irritating the root of the vagus, and the 

 shme muscles were thrown into contraction by irri- 

 tation of the root of the accessory. He also per- 

 ceived contractions in the stylo-pharyngeus from 

 irritation of the root of the glosso-pharynseal nerve, 

 as in the experiments of Mayo and Volkmann, 

 Muller's Archives, Heft iii. 1844. S. 297. 



ft Archives Generates de Med. 1844. 



