782 



THE XKRVOrS SYSTEM 



ANTERIOR PRIMARY DIVISIONS 



The anterior divisions of the spinal nerves (with the two exceptions above men- 

 tioned) are hirger than the posterior divisions, and each is connected by one or two 

 rami commimicantes with the ganglionated cord of the sympathetic. In the cervi- 

 cal, lumbar, sacral, and coccygeal regions they combine to form plexuses; in the 

 thoracic region each nerve takes for the most part an independent course, and its 

 typical division into a lateral or dorsal, and an anterior or ventral branch is very 

 obvious. This division, however, is not confined to the dorsal nerves; it is recog- 

 nisable, though with more difficulty, in the lower cervical, lumliar, and sacral 

 regions, and it cannot be clearly distinguished in the upper cervical and coc- 

 cygeal regions. 



CERVICAL NERVES. — The anterior primar}^ divisions of the upper four cervical 

 nerves are of moderate size; each is connected by one or two branches with the 

 superior cervical ganglion of the sympathetic, and they unite with one another to 

 form a looped plexus, the cervical plexus. The anterior primary division of 



LESSER 

 OCCIPITAL 



TO RECTrS 



CA PITIS 

 LATERALIS 



TO RECTUS 



CA PITIS 



AMICUS 



MINOR 



AND MAJOR 



STERyO- 

 MASTOID 



SCALENUS 

 M EDI US 



LEVATOR 

 ANGULI 



SCA PULJE 



SCALE.VrS 



MEDIUS 

 LEV. A.VG. 

 SCAPULA 



FROM FIFTH 

 CERVICAL 



PHRENIC 



Fui. 453. — Diagram of the Cervical Plexus. 



PERFICIAL 



HYPOGLOSSAL 



TO GENIO- 

 HYOID 



TO THYRO- 

 HYOID 



TO OMOHYOID 



TO STERNO-HYOID 



TO STERNO- 

 THYROID 



TO OMO-HYOin 

 (POST-BEI.l.Y) 

 TO TRAPEZIUS 



SUPRA- 



ACROMIAL 



SUPRA- 

 CLA VICULAR 



SUPRA- 

 STERNAL 



\ 



the first cervical nerve, smaller than the posterior division, passes outwards in the 

 groove on tlie posterior arch of the atlas beneath the vertebral artery, turns 

 forwards ])etween the vertebral artery and the lateral mass of the atlas, and bends 

 downwards in front of the transverse process of that l)one to unite witli the second 

 nerve. The anterior division of the second nerve runs outwards behind the superior 

 articular process of the axis, passes behind and to the outer side of the verteljriil 

 artery and in frtint of the second posterior intertransverse muscle to the interval 

 between the scalenus medius and the rectus capitis anticus major, where it unites 

 with the first and third nerves. The anterior divisions of the third and fourth 

 nerves, after their exits from the intervertebral foramina, pass behind the verte- 

 bral artery and between the anterior and posterior intertransverse muscles to 

 appear in tlie intersi)ace between th(> rectus capitis antieus major and the s('alenus 



