ANTERIOR PRIMARY DIVISIONS OF CERVICAL NERVES. 283 



with each other by a loop on the back of the sacrum, and the lowest is joined in a 

 similar manner with the coccygeal nerve ; one or two filaments from these sacral 

 nerves are distributed in the neighbourhood of the coccyx. 



COCCYGEAL NERVE. The posterior division of the coccygeal nerve is very small, 

 and separates from the anterior primary portion of the nerve in the sacral canal. 

 It is joined by a communicating filament from the last sacral nerve, and ends in 

 the integument over the posterior surface of the coccyx. 



ANTERIOR PRIMARY DIVISIONS OF THE SPINAL NERVES. 



The anterior primary divisions of the spinal nerves are distributed to the parts 

 of the body situated in front of the vertebral column, including the limbs. They 

 are, for the most part, considerably larger than the posterior divisions, and each 

 is connected by one or two slender filaments with the sympathetic. Those of the 

 cervical, lumbar, and sacral nerves form plexuses of various forms ; but those of 

 the dorsal nerves remain for the most part separate from one another. 



CERVICAL NEKVES. 



The anterior divisions of the upper four cervical nerves form the cervical plexus. 

 The first emerges between the rectus lateralis and rectus anticus minor muscles ; 

 and the others, having passed behind the vertebral artery and between the two 

 intertransverse muscles, appear at the side of the neck between the scalenus medius 

 and rectus anticus major muscles. They are each united by a communicating filament 



Fig. 189. CUTANEOUS DISTRIBUTION OF THE POSTERIOR PRIMARY BRANCHES OF THE SPINAL 



NERVES. (GK D. T.) 



On the right side the nerves are shown lying on the superficial muscles ; on the left side the limit of 

 the skin-area supplied by these nerves is indicated by the dotted line. 7 c, seventh cervical spine ; 6 c?, 

 sixth dorsal ; 12 d, twelfth dorsal ; 5 I, fifth lumbar. 



The nerves are indicated as follows : C II, great occipital, from second cervical ; III to V, third to 

 fifth cervical ; D I, first dorsal ; II to XII, second to twelfth dorsal ; three cutaneous branches are given 

 by the sixth dorsal, two from the internal, and one from the external division ; L, lumbar ; S, upper 

 sacral ; C, lower sacral and coccygeal ; A S C, anterior divisions of the last sacral and coccygeal ; P C, 

 perforating cutaneous ; S S, small sciatic 



to the first cervical ganglion of the sympathetic nerve, or to the cord connecting that 

 ganglion with the second. 



The anterior divisions of the lower four cervical nerves, larger than the upper 

 four, appear between the anterior and middle scaleni muscles, and, together with 

 the larger part of the first dorsal, go to form the brachial plexus. They are each 

 connected by a filament with one of the two lower cervical ganglia of the sympathetic, 

 and with the plexus on the vertebral artery. 



The anterior divisions of the first and second nerves require a notice separately 

 from the description of the nerves of the cervical plexus. 



SUBOCCIPITAL NERVE. 



The anterior primary division of the first nerve runs forwards in a groove on the 

 outer side of the upper articular process of the atlas, and bends downwards in front 

 of the transverse process of that vertebra to join the second nerve. In this course 

 forwards it lies beneath the vertebral artery, and on the inner side of the rectus 

 lateralis muscle, to which it gives a branch. As it crosses the inner side of the 

 foramen in the transverse process of the atlas, the nerve is joined by a filament 

 from the sympathetic on the vertebral artery. From the loop which it makes in 

 front of the transverse process, twigs are supplied to the two anterior recti muscles, 

 and one or two larger branches pass to the hypoglossal trunk, in connection with 

 which most of the fibres pass down into the descending cervical nerve (p. 273). 



