SPINAL ACCESSORY NERVE. 



747 



the posterior and anterior spinal nerves at 

 their origin. 



The spinal accessory in its course within 

 the spinal canal frequently forms communi- 

 cations with the posterior root of the first 

 cervical, and much more seldom with the 

 posterior root of the second cervical nerve.* 

 When these communicating filaments come 

 from the second cervical, they are generally 

 few in number. This communication between 

 the spinal accessory and the posterior root of 

 the first cervical is, according to Lobstein, 

 more frequently present than absent. f When 

 the posterior root of the first cervical joins 

 itself, either in whole or in part, to the spinal 

 accessory, a branch of equal size generally leaves 

 the accessory, either at the point where it is 

 joined by the posterior root of the first cervi- 

 cal, as figured and described by Asch J, or a 

 little above this junction, as figured by Hu- 

 ber, and described by Bellingeri.|| This 

 branch, after leaving the accessory, proceeds 

 outwards, approaches the anterior root of 

 the first cervical, and takes the place of the 

 posterior root of that nerve.H When the 

 posterior root comes from the accessory, 

 it generally presents a ganglion in the usual 

 position. Sometimes, however, though rarely, 

 this ganglion is found on the accessory where 

 the posterior root of the first cervical leaves 

 it to join itself to the anterior root. This 

 ganglion was first pointed out by Huber ; its 

 existence has been denied by Lobstein, Asch, 

 Haller, and Scarpa, and it has again been 

 described by Bellingeri. I have seen this gan- 

 glion twice, and it was present on one side 

 only. It becomes an interesting question in 

 a physiological point of view to know, whether 

 or not the whole of the filaments of the pos- 

 terior roots of the spinal nerves which join 

 themselves to the accessory, again leave it 

 to form the posterior root of the first cervical. 

 Bellingeri answers this question in the affirm- 

 ative. " The filaments," he says, " coming 

 from the posterior roots to the accessory are 

 not intermixed, but only approximated, so that 

 they can be separated by slight traction."** 



* Scarpa states (opus cit. p. 395.) that in a great 

 number of bodies he examined with a special refer- 

 ence to this point, he found a communication be- 

 tween the accessory and the posterior root of the 

 second cervical only in two instances. 



f Circa harum radicularum, quae pro radicibus 

 posticis primi paris habenter, communicationem 

 illud notamus, quod saepius accessorium subire, quam 

 eundem intactum relinquere observenter. Opus cit. 

 p. 223. 



J De Primo Pare Nervorum Medullas Spinalis, 

 tab. x. fig. 2. ; et explicatio, p. 335. Ludwig Scrip. 

 Nevr. Min. Sel. torn. L 

 Opus cit. 



|| Opus cit. p. 80. Monro secundus has also given 

 a representation of this communication between the 

 accessory and posterior root of the first cervical. 

 Observations on the Structure and Functions of the 

 Nervous System, tab. x. fig. 2. 1783. 



f Bischoff states (opus cit. pp. 34. 82.) that in 

 none of the numerous instances in which he dis- 

 sected the accessory in the lower animals, did he 

 ever observe any filaments of the posterior roots of 

 the spinal nerves join themselves to it. 

 ** Opus cit. p. 81. 



And in another place he says, " I believe that 

 the filaments from the posterior roots, which 

 join the accessory, leave it again to proceed 

 to the posterior root of the first cervical."* 

 From this he concludes that the accessory 

 contains no sensiferous filaments. Miiller, on 

 the other hand, has adduced some unusual 

 anatomical arrangements in this nerve, which 

 may be regarded as favouring the opinion that 

 it contains sensiferous filaments independant 

 of those which it may receive from the pos- 

 terior roots of the spinal nerves. He men- 

 tions an instance f, which he elsewhere J 

 describes at considerable length, where the 

 posterior root of the first cervical nerve on 

 the right side was not present, and where its 

 place was supplied by two bundles of fila- 

 ments from the superior part of the spinal 

 accessory. The upper of these bundles, at 

 least, came from the medulla oblongata. 

 Upon the posterior root of the first cervical 

 thus constituted, a ganglion was formed while 

 it was still within the iheca vertebralis. The 

 upper fibres of the posterior root of the 

 second cervical of this side joined themselves 

 to the accessory, but no nervous filaments 

 were attached to the spinal chord in the usual 

 position of the posterior root of the first 

 cervical. On the left side, the posterior 

 root of the first cervical presented its usual 

 appearance, and was connected to the spinal 

 accessory by some filaments of communi- 

 cation. The filaments of the accessory arising 

 from the medulla oblongata did not, as on the 

 right side, divide themselves into two parts, 

 one of these becoming the substitute of the 

 posterior root of the first cervical : but the 

 whole ran upwards into the accessory nerve. || 

 Miiller also states that Hyrtl has often seen 

 a ganglion upon the accessory nerve opposite 

 the entrance of the vertebral artery into the in- 

 terior of the cranium ; and that Remak showed 

 him an instance of a ganglion upon the spinal 

 accessory at its passage through the foramen 

 lacerum. " I do not, however, affirm," Miil- 

 ler remarks in reasoning from these cases, 

 " that the spinal accessory always contains 

 originally sensiferous filaments, but leave it 

 doubtful." " But in the case," he continues, 

 " where the nervus accessorius forms an inti- 

 mate connection with the posterior root of 

 the first cervical, or any other nerve, we may 

 suppose an interchange ; and this, in the same 

 degree, will render probable the idea of Monro, 



* Ibid, p. 79. 



f Archiv. fur Anat. und Physiol. 1834, p. 12. 



t Idem opus, 1837, pp. 279281. 



Arnold (Bemerkungen tiber den Bau des Hirns 

 und Ruckenmarks, &c., S. 181183 ; Zurich, 1838) 

 has published remarks upon this anomalous instance 

 in the origin of the posterior root of the first cervical 

 from the accessory, the object of which is to en- 

 deavour to show that Miiller had misinterpreted 

 the facts observed. Among other things urged 

 with this view, is the circumstance that the pos- 

 terior root of the first cervical does not arise usually 

 in the same line with the posterior roots of the 

 other spinal nerves, but somewhat anterior to these. 

 We cannot, however, believe that so experienced 

 and accurate an anatomist as Miiller is, could fall 

 into any such mistake as is here insinuated. 



