|82 



PAR VAGUM. 



of the lungs and stomach, and hence its appel- 

 lation of pneu mo-gastric. 



The nervus vagus arises by several filaments, 

 generally from six to ten, from the restiform body 

 of the medulla oblongata, parallel to and a little 

 posterior to the groove between the olivary and 

 restiform bodies, and from a line to a line and a 

 half distant from the posterior edge of the olivary 

 body. Thearciform bandof superficial filaments 

 passing between the anterior pyramidal and res- 

 tiform bodies cross among the lower filaments 

 of this nerve. The filaments of the vagus are 

 attached to the restiform body in a vertical, 

 straight, and thin band of from three to four 

 lines in length, the upper end of which is sepa- 

 rated from the lower edge of the glosso-pha- 

 ryngeal nerve by a few small bloodvessels only. 

 The upper half of these filaments of the vagus 

 are at their origin closely approximated, so that 

 the lower edge of the one above is in contact 

 with the upper edge of the one below, while 

 the lower filaments, especially the two last, are 

 considerably more distant from each other. 

 The lowest filament is placed only a little 

 above and in the same line with the uppermost 

 filament of the spinal accessory, and it is fre- 

 quently difficult to determine where the fila- 

 ments of the accessory begin, and where those 

 of the vagus end. From this origin each vagus 

 proceeds forwards and outwards between the 

 lower surface of the lateral lobe of the cerebel- 

 lum and that portion of the dura mater cover- 

 ing the basilar process of the occipital bone, to 

 reach the foramen lacerum posterius, through 

 the anterior part of which opening it escapes 

 from the interior of the cranium. In this part 

 of its course it frequently anastomoses with 

 the glosso-pharyngeal, and its filaments be- 

 come more subdivided, but at the same time 

 more closely aggregated, so that it is thicker 

 and narrower. On reaching the foramen lace- 

 rum posterius it enters a sheath or canal in the 

 dura mater, anterior and a little internal to the 

 commencement of the internal jugular vein, 

 immediately anterior to the spinal accessory 

 tierve, and posterior to the glosso-pharyngeal. 

 As these three nerves enter the foramen lace- 

 rum, they perforate the dura mater, the glosso- 

 pharyngeal by a separate and distinct opening, 

 the nervus vagus and spinal accessory by an 

 opening common to both. Sometimes there is 

 a small bridle of dura mater, at other times 

 only a fold of the arachnoid separating the 

 vagus and accessory at this part. At the lower 

 part of the foramen lacerum the npinal acces- 

 sory is closely applied to the posterior surface 

 of the vagus. The dura mater is prolonged 

 downwards into the foramen lacerum upon 

 these three nerves in the form of two sheaths, 

 one sheath surrounding the glosso-pharyngeal, 

 and the other the vagus and accessory. From 

 the proximity of these three nerves, as they 

 pass through the foramen lacerum posterius, 

 and from their intimate connection in some 

 parts of their course and subsequent distribu- 

 tion, they were long considered to form only a 

 single nerve. 



As the vagus lies in the foramen lacerum 

 it presents a greyish oblong swelling, resem- 



bling the ganglion on the posterior root of 

 a spinal nerve (ganglion primum nervi vagi 

 of Wutzer, ganglion radicis n. v. of Bendz, 

 ganglion superiits n.v., ganglion jitgulare n.v.) 

 This ganglionic enlargement begins immedi- 

 ately after the nerve has entered the foramen 

 lacerum, so that its upper edge may be some- 

 times seen from within the cranium ; it is of an 

 oval form, and it extends along the course of 

 the nerve from a line and a half to two lines.* 

 Mr. James Spencef has pointed out that a 

 small filament belonging to the lower part of 

 the vagus passes over the posterior surface of 

 this ganglion without entering it, and joins 

 itself to the superior filaments of the spinal 

 accessory. J This fact, as we shall afterwards 

 find, has a direct bearing upon the physiology 

 of the nerve. A communicating filament passes 

 between the ganglion superiusof the vagus and 

 the superior cervical ganglion of the sympathe- 

 tic, another between it and the ganglion petro- 

 sum of the glosso-pharyngeal, (vide article 

 GLOSSO-PHARYNGEAL,) and one or more be- 

 tween it and the spinal accessory . From the 



* Arnold (Der Kopftheil des vegetativen Ner- 

 vensystems beim Menschen. S. 107) describes this 

 ganglion as varying little in size, and as measuring 

 a line and a half to a line and three quarters in 

 breadth, a line to a line and a half in length, and 

 three quarters to one liue in thickness. He found 

 a difference of about two lines between the mea- 

 surement of the circumference of the ganglion and 

 the trunk of the nerve immediately below, the for- 

 mer generally measuring five and the latter three 

 lines. Bischoff (Nervi Accessorii Willisii Anato- 

 mia et Physiologia, 1832, p. 20) gives the same 

 measurements as those of Arnold, from whom he has 

 evidently copied them. Bendz (De Connexu inter 

 Nervum Vagum et Accessorium Willisii, 1836, 

 p. 17J describes it as a rounded ganglion, somewhat 

 Battened, measuring about two lines in the antero- 

 posterior diameter, and nearly two lines in the 

 vertical direction. Valentin (Sbemmerring's Vom 

 Baue des Menschlichen Korpers, Him und Ner- 

 venlehre. Vierter Band. 1841. S. 482) describes it 

 as an oblong rounded swelling, somewhat flattened, 

 and about from aline and three quarters to two and 

 a half lines in length. 



t Kdinburgh Medical and Surgical Journal, 

 No. 153, 1842. 



J Remak (Froriep's neue Notizen for 1837, 

 No. 54) states that some of the filaments of the 

 vagus do not pass through this superior yanylion of 

 the vagus in the dog, cat, and rabbit; and Volk- 

 mann (Miiller's Archives, Heft v. 1840) confirms 

 this observation of Remak on the dog ; and further 

 mentions that the same enlargement exists in the 

 sheep, while in the calf all the filaments pass 

 through the ganglion. The accuracy of such dis- 

 sections, especially those made on the human spe- 

 cies, and the physiological inferences deduced from 

 them, have been called in question, (e.g. Hein in 

 Muller's Archives tor 1844, p. 336, and Bischoff, in 

 the same work for 1833, p. 156), on the grounds 

 that this anatomical arrangement is not constant, 

 and besides that it is difficult to distinguish between 

 the lower fibres of the root of the vagus and the 

 upper fibres of the root of the nervus accessorius. 



Bendz describes and delineates (De Connexu 

 inter Nervum Vagum et Accessorium Willisii. Tab.i. 

 Hannia?, 1836) two small communicating filaments 

 passing between the spinal accessory and the gan- 

 glion jngulare of the vagus. Valentin (Sbemmer- 

 ring Vom Baue des Menschlichen Korpers, Him 

 und Nervenlehre. Vierter Band, 1841) describes a 

 similar anastomosis. Arnold (Icones Nervorum 



