SPINAL NERVES. 



751 



trapezius, passes through the latter, and ter- 

 minates in the skin in the occipital region as 

 the great occipital nerve, coursing along with 

 the occipital artery but lying internal to it. 

 Before becoming great occipital, it gives off at 

 the lower border of the inferior oblique a 

 branch to supply this muscle and a superior 

 and inferior anastomotic branch to commu- 

 nicate with the first and third cervical. When 

 passing along the anterior surface of the com- 

 plexus, numerous branches are given off to 

 this muscle, the trapezius, and splenius. Those 

 for the last muscle are more numerous and 

 larger than the branches, for the two others 

 are directed to the anterior aspect of the 

 muscle, and one or more of them perforate the 

 complexus before reaching it. 



The posterior branch of the third cervical is 

 smaller than the second, but larger than the 

 fourth, and situated more externally, emerg- 

 ing from between the transverse processes of 

 the second and third cervical vertebra. It is 

 directed inwards, between the opposed surfaces 

 of the complexus and semispinalis colli to wards 

 the median line, and having reached the sides 

 of the spinous processes of the vertebrae, di- 

 vides into ascending and horizontal cutaneous 

 branches. The ascending branch, after a short 

 course, perforates the inner border of the 

 complexus and trapezius, and becomes cuta- 

 neous. It continues its course close to the 

 median line, as far as the region of the oc- 

 ciput, the inner and lower part of which it 

 supplies on the internal side of the great occi- 

 pital nerve. 



The horizontal branch passes between the 

 ligamentum nuchae and the inner border of 

 the complexus, and after having perforated 

 the tendon of the trapezius, terminates in ex- 

 ternal small cutaneous filaments. The nerve 

 prior to division, and at the outer border of 

 the semispinalis colli, communicates by one 

 or more filaments with the posterior branch 

 of the second cervical. From the anastomosis 

 between the communicating branches of the 

 posterior roots of the three first cervical nerves, 

 results an irregular plexus placed between 

 the complexus and outer part of the semi- 

 spinalis colli, and consequently nearly in a line 

 with the transverse processes of the superior 

 cervical vertebrae. From this posterior cervical 

 plexus, numerous branches arise to supply the 

 complexus, splenius, and semispinalis colli. 

 The anastomosis between these posterior 

 branches is, according to Cruveilhier, some- 

 times deficient. 



The posterior root of the fourth cervical nerve 

 varies much as to individual size, but is al- 

 ways smaller than the preceding. It passes 

 downwards and inwards between the com- 

 plexus and semispinalis colli, and having 

 reached the side of the median line, perforates 

 the tendons of the splenius and trapezius, and 

 becomes culaneous. In its course it supplies 

 these muscles, and occasionally terminates 

 in the splenius without going to the skin. 



The posterior branches of the fifth, sixth, 

 seventh, and eighth cervical nerves have a 

 similar course to the fourth, but decrease in 



size from above downwards. The fifth and 

 sixth usually pass between the opposed sur- 

 faces of the semispinalis colli and complexus, 

 give branches to these muscles, and perforate 

 the inner part of the tendons of the splenius 

 and trapezius, to terminate in the skin at 

 the lower part of the nape of the neck. 



The posterior branches of the seventh and 

 eighth cervical nerves pass either through the 

 deep-seated fibres of the semispinalis colli, or 

 between it and the multifidus spinse, give 

 branches to these two muscles, perforate the 

 tendons of the trapezius and splenius, and 

 terminate by ramifying, the one on the skin 

 above the scapula, the other over the integu- 

 ment, as far as about the spinous process of 

 the third dorsal vertebra. The inter-trans- 

 versaies muscles, cervicalis ascendens, tra- 

 chelo-mastoid, and transversalis colli, receive 

 numerous small filaments from these nerves 

 almost immediately after their appearance in 

 the neck. 



The posterior branches of the dorsal (tho- 

 racic) nerves are much smaller than the an- 

 terior, and are directed backwards between 

 the ascending costo-transverse ligaments and 

 the sides of the vertebrae. Having reached 

 the outer border of the semispinalis dorsi and 

 multifidus spinae, they divide into external and 

 internal branches, the latter being muscular 

 and cutaneous in their distribution, the former 

 only muscular in the eight upper. In the 

 first eight the internal branches are larger, 

 in the last four much smaller than the ex- 

 ternal. 



The external or muscular branches of the 

 eight superior pass between the sacro-lum- 

 balis and longissimus dorsi, and give off nu- 

 merous filaments to supply these muscles, and 

 the levatores costarurn ; that of the first send- 

 ing a few filaments to the cervicalis ascendens, 

 trachelo-mastoid, transversalis colli, and sca- 

 leni muscles. 



The internal branches wind either over the 

 posterior aspect of the semispinalis dorsi, or 

 between it and the multifidus spinse, and 

 having supplied these muscles with numerous 

 filaments, reach the sides of the spinous pro- 

 cesses ; here they perforate the rhomboid, 

 latissimus dorsi, and trapezius, the last muscle 

 very obliquely, and become cutaneous, being 

 principally distributed to the skin at the back 

 part of the scapular region. 



The external branches of the four inferior 

 pass obliquely downwards and outwards be- 

 tween the sacro-lumbalis and longissimus 

 dorai, communicating with each other in their 

 course, and at the outer border of the former 

 muscle perforate the tendon of the latis- 

 simus dorsi, and become cutaneous, some of 

 the lower filaments being capable of being 

 traced over the glutaeal region. 



The internal branches of the four inferior are 

 remarkably small, and are lost either in the 

 substance of the multifidus spinse, or semi- 

 spinalis dorsi. The cutaneous filaments from 

 the posterior branches of the dorsal nerves 

 given off on the one hand from the internal, 

 and on the other from their external divisions^ 



