750 



SPINAL NERVES. 



branch of the spinal accessory is a motor 

 nerve. We found that when it was embraced 

 firmly within the forceps, or tied tightly soon 

 after it had emerged from the foramen lacerum, 

 the animal gave indications of suffering* ; but 

 an experiment of this kind does not enable us 

 to decide whether these sensiferous filaments 

 were originally contained in the accessory, or 

 were derived from the neighbouring nerves. 

 Mr. Shaw has detailed an experiment to show 

 that the movements which it imparts to the 

 sterno-mastoid, and to the trapezius are not 

 voluntary, but respiratory.f In our experi- 

 ments, and in those subsequently performed 

 by Bernard, these muscles acted in unison 

 with the muscles of respiration after the spinal 

 accessory nerves had been divided. 



While all experimenters agree that the ex- 

 ternal branch of the accessory is chiefly if not 

 entirely composed of motor filaments, they 

 have arrived at discrepant conclusions re- 

 garding the functions of the internal branch. 

 Volkmann J, Van Kempen , and Stilling ||, 

 observed no movements of the muscles in 

 which the internal branch of the accessory 

 is distributed, on irritating the roots of this 

 nerve within the cranium ; while in those 

 of Bischoff, my own, those of Valentin^!, Lon- 

 get**, Heinff, MorgantiJJ, and Bernard , 

 partly consisting of irritating the roots of the 

 nerve within the cranium after death, and 

 partly, as in those of Bischoff, Longet, Mor- 

 ganti, and Bernard, by lesions of the nerve 

 in living animals, and observing their effects 

 upon the movements of the muscles in which 

 it is distributed, proofs of its being a motor 

 nerve were believed to be obtained. We 

 think that this evidence is sufficiently strong 

 to justify the belief that the internal branch of 

 the accessory does contain motor filaments; 



* Edinburgh Medical and Surgical Journal for 

 January, 1838. Valentin states (opus cit. pp. 58. 

 62.) that he succeeded in increasing the action of 

 the heart by irritating the trunk of the accessory ; 

 but Van Kempen (opus cit. p. 65) repeated this 

 experiment without success. 



f London Medical and Physical Journal, vol. xlix. 



J Miiller's Archiv. 1840. 



Essai Experimental sur la Nature Fonctionelle 

 du Nerf Pneumogastrique : Louvain, 1842. In 

 giving the results of Van Kempen's experiments in 

 the art. PARVAGUM, foot-note at p. 891, vol. iii. upon 

 the effects of irritating the roots of the vagus within 

 the cranium, 1 have inadvertently written the pa- 

 lato-glossus muscle instead of the palato-pharvngeus 

 or pharyngo-staphylin muscle, as one of the muscles 

 seen to contract in this experiment. I may also 

 here correct another error in the same article : at 

 p. 900, it is stated that Longet believes that the 

 secretion of the gastric juice is greater after section 

 of the vagi than in the sound animal ; while in fact 

 he states that it is diminished by section of the 

 vagi, and that this diminution in the secretion may 

 be explained on mechanical grounds. 



|| Bischoff's Bericht tiber die Fortschritte der 

 Physiologic im Jahre 1842, S. 154. In Muller's 

 Archiv. 1843. 



^[ Opus supra cit. 



** Opus supra cit. 



ft Muller's Archiv. 1844. 



it Omodei, Annali Universal! di Medicina. Juli, 

 1843. 



Opus supra cit. 



but it is at the same time highlv probable that 

 it is partly composed of sensiferous and afferent 

 filaments, and if so, its constitution must be 

 similar to the vagus nerve, with which it be- 

 comes so closely incorporated. In the art. 

 PAR VAGUM, sufficient proof has been ad- 

 duced to satisfy us that the opinion that the 

 spinal accessory furnishes all the motor fila- 

 ments contained in the trunk of the vagus, is 

 no longer tenable. 



(John Reid.) 



SPINAL NERVES (Les Nerfs rachidiens, 

 Fr. ; Die Ruec/cenmarksnerven, Germ. ; I Nervi 

 Spinali, Ital.) are thirty-one pairs, and are dis- 

 tributed to the neck, and the upper extremi- 

 ties, the trunk and lower extremities. They 

 are divided into Cervical, Dorsal, Lumbar and 

 Sacral : the first division comprising eight ; 

 the second, twelve ; the third, five ; and the 

 fourth, six. Their general and special cha- 

 racters, and their apparent and absolute con- 

 nexion with the spinal chord having been 

 already described*, we shall limit the details 

 of this article to their ultimate distribution. 



Each spinal nerve, after the union of its 

 roots, divides into an anterior and posterior 

 branch, the former having generally a much 

 more complicated and extensive distribution 

 than the latter. It will be convenient there- 

 fore for the purpose of description to enter 

 first into a consideration of the posterior 

 branches. 



The posterior branch of the first cervical or 

 sub-occipital nerve is larger than the anterior, 

 and passes internal to and below the vertebral 

 artery, between the arch of the atlas and the 

 occipital bone, to gain the triangular space be- 

 tween the rectus capitis posticus major, the su- 

 perior and inferior oblique muscles. It is here 

 imbedded in a considerable quantity of fat and 

 dense cellular membrane, and having directed 

 itself from before, back wards, and slightly from 

 below up wards, divides into a series of branches. 

 Two external branches are sent to the two 

 oblique muscles: an internal ascends to the 

 rectus capitis posticus major, and which 

 having supplied this, terminates in the minor : 

 another filament is directed to the anterior 

 aspect of the complexus near to its occipital 

 attachment: and the terminal branch descends, 

 generally perforating the inferior obliquely, 

 and anastomoses with the posterior branch of 

 the second cervical nerve. 



The posterior branch of the second cervi- 

 cal nerve emerges from between the lower 

 border of the posterior arch of the atlas, and 

 the lamina of the axis, and is larger than 

 any of the posterior branches of the cervical 

 nerves, and three or four times greater than 

 the anterior branch of the same nerve. It 

 appears at the lower border of the inferior 

 oblique, and having passed a short distance 

 horizontally inwards, winds round this muscle 

 to the anterior aspect of the outer part of the 

 complexus, which it perforates. It inclines 

 outward and upwards between it and the 



* Vide NERVOUS SYSTEJI, vol. iii. p. 657. 



