884 



PAR VAGUM. 



nold was the first who described the ramus 

 auricularis in the human species. 



Passage of the vngus along the neck to the 

 origin of the inferior or recurrent laryngeal 

 branch After the vagus emerges from the in- 

 ferior aperture of the foramen lacerum poste- 

 rius, it lies between the internal carotid artery 

 and the internal jugular vein, the artery being 

 internal and anterior, and at first separated a 

 small distance from it, the vein being immedi- 

 ately posterior and external. The glosso-pha- 

 ryngeal is still placed on its anterior side, but 

 soon leaves it and crosses the anterior surface 

 of the internal carotid artery on its way to the 

 root of the tongue. The spinal accessory is 

 still on its posterior side, but a little above the 

 transverse process of the atlas the external 

 branch begins to diverge backwards and out- 

 wards, and passes beneath the upper part of 

 the internal jugular vein to reach the inner sur- 

 face of the upper part of the sterno-cleido- 

 mastoid muscle. The sympathetic nerve lies 

 immediately posterior to it. The hypoglossal 

 approximates its outer edge immediately below 

 the foramen lacerum, gradually gets upon its 

 anterior surface, is seen emerging from the 

 angle left between it and the external branch of 

 the accessory, where these nerves begin to sepa- 

 rate, and opposite the transverse process of the 

 atlas, or sometimes a little below this, it has 

 crossed over its anterior edge, and proceeds 

 forwards and inwards to reach the tongue. The 

 hypoglossal, in crossing over the anterior sur- 

 face of the vagus, is very closely bound to it by 

 cellular tissue, and some small communicating 

 branches pass between them. Some small 

 communicating branches also pass between this 

 portion of the vagus and the external branch of 

 the spinal accessory, the superior ganglion of 

 the sympathetic, the glosso-pharyngeal, and the 

 nervous loop formed by the anterior branches 

 of the first and second cervical nerves in front 

 of the transverse process of the atlas. The 

 vagus also in this part of its course generally 

 sends a branch to join the descendens noni, 

 and more rarely the descendens noni is almost 

 entirely or altogether formed by this branch of 

 the vagus.* All these nerves and bloodvessels 

 in the upper part of the neck are surrounded 

 and connected together by cellular devoid of 

 adipose tissue. The vagus, after joining itself 

 to the internal carotid artery, accompanies it to 

 the point of bifurcation of the common carotid, 

 and then continues its course down the neck, 

 enclosed in the same sheath with the common 

 carotid and internal jugular vein, the artery 

 being internal, and the vein external and also 

 anterior. The nerve maintains the same rela- 

 tion to these two vessels on both sides as far as 

 the lower part of the neck, where on the right 

 side the artery and vein diverge from each 

 other, the artery passing inwards and the vein 

 outwards, to join itself to the vena innominata; 

 while on the left side the vein and artery have 



* Krause (Handhnch der Menschlichen Anato- 

 mic, S. 1053 & 1063. Hannover, 1842) states 

 that probably these strengthening filaments of the 

 vagus furnish the cardiac branch of the descendens 

 noni. 



scarcely separated from each other, when the 

 junction between the former and left subclavian 

 vein takes place. On the right side the nerve 

 is seen lying in the interval between the inter- 

 nal jugular and the internal carotid, and while 

 crossing the anterior surface of the right sub- 

 clavian artery nearly at right angles, it sends off 

 the right inferior laryngeal or recurrent nerve. 

 On the left side it passes downwards into the 

 thorax, still lying close to the outer side of the 

 left common carotid ; but as it proceeds onwards, 

 it crosses obliquely the left subclavian artery 

 near its origin, and passing over the transverse 

 portion of the arch of the aorta, it there gives 

 off the left inferior laryngeal nerve. On both 

 sides it passes into the thorax beneath the vena 

 innominata. 



The vagus, on emerging from the foramen 

 lacerum, is near to the outer edge of the 

 rectus capitis anticus minor muscle and in 

 front of the rectus capitis lateralis ; in its pas- 

 sage down the neck it first crosses the anterior 

 surface of the lateral part of the atlas, then 

 proceeds along the anterior surface of the rectus 

 capitis anticus major muscle, and lastly it de- 

 scends upon the longus colli. In the upper 

 part of its course it lies deep, and crosses be- 

 neath the styloid process of the temporal bone 

 and stylo-pharyngeus muscle. In the middle 

 of the neck the two vagi nerves have approached 

 nearer to each other, and are much more su- 

 perficial. In the lower part of the neck they 

 are again placed deeper, and are covered by 

 the sterno-hyoid, sterno-thyroid, and sterno- 

 cleido-mastoid muscles. 



As the vagus emerges from the lower part 

 of the foramen lacerum, its fibres are arranged 

 somewhat loosely together, and are not 

 enclosed in any dense and compact neuri- 

 lema, so that it is larger here than at the 

 lower part of the neck ; and when the cellular 

 tissue surrounding it is removed, the outline of 

 the superficial fibres can be readily traced. 

 About half an inch below the lower edge of 

 the superior ganglion it enlarges still more, 

 forming an oblong rounded swelling, from nine 

 lines to an inch in length, and extending from 

 about the transverse process of the atlas to 

 midway between the transverse processes of the 

 second and third cervical vertebrae (plexus gan- 

 gliformis nervi vagi, ganglion secundum n.v. 

 of Wutzer, gang/ion trunci n. v. of Bendz, 

 ganglion infer ins n.v.) In the human species, 

 though this swelling has a greyish colour, yet 

 its appearance is that of a plexus more than of 

 a true ganglion ; and Valentin states* that he 

 has not yet obtained satisfactory evidence that 

 it contains the ganglionic nucleated globules 

 without the presence of which there can be no 

 true ganglion, and he believes that the greyish 



* In many of the Mammalia this swelling is 

 more circumscribed and less elongated than in the 

 human species, and forms a very distinct and true 

 ganglion. Bischoff (oper. cit. tab. ii.) has given 

 representations of it in the cat, fox, sow, mole, 

 and weasel ; and Mr. E. Cook, (Guy's Hospital 

 Reports, vol. ii. p. 311,) in the guinea-pig, dog, 

 and sheep. In all these animals it occupies that 

 part of the trunk of the vagus from which the supe- 

 rior laryngeal nerve arises. 



