SUB-OCCIPITAL NERVE. 115 



The nerve furnishes muscular offsets to the sterno-mastoideus and the 

 trapezius. 



The HYPO-GLOSSAL NERVE (ninth of Willis), issuing from the cranium 

 by the anterior condyloid foramen, lies deeply between the internal carotid 

 artery and the jugular vein (fig. 25, *). It next comes forwards between 

 the vein and artery, turning round the outer side of the vagus to which it 

 is united. The nerve now descends in the neck, and becomes superficial 

 below the digastric muscle in the anterior triangular space ; from this spot 

 it is directed inwards to the tongue and its muscles. 



* Connecting branches. Near the skull the hypo-glossal is united by 

 branches with the vagus nerve, the two being almost inseparably joined. 



* Rather lower down the nerve is connected by offsets with the sympa- 

 thetic, and with the loop of the first two spinal nerves. 



The branches for distribution have been met with in the foregoing dis- 

 sections. Thus in the neck it supplies, in union with the spinal nerves, 

 the depressors of the hyoid bone. In the submaxillary region it furnishes 

 branches to one elevator (genio-hyoid) of the os hyoides ; to the extrinsic 

 muscles of the tongue except the palato and pharyngeo-glossus ; and to all 

 the intrinsic of the tongue. 



Dissection. The small rectus capitis lateralis muscle, between the 

 transverse process of the atlas and the base of the skull, is now to be cleaned 

 and learnt. At its inner border the anterior branch of the first cervical 

 nerve, which forms part of a loop on the atlas, is to be found. 



The RECTUS CAPITIS LATERALIS (fig. 25) is small and thin, and repre- 

 sents an intertransverse muscle. It arises from the anterior transverse 

 process, and the tip of the united transverse processes of the atlas ; and is 

 inserted into the jugular eminence of the occipital bone. 



On the anterior surface rests the jugular vein ; and in contact with the 

 posterior is the vertebral artery. To the inner side lies the anterior pri- 

 mary branch of the first cervical nerve. 



Action, It assists the muscles attached to the mastoid process in in- 

 clining the head laterally. 



Dissection. For the purpose of tracing backwards the anterior branch 

 of the first cervical nerve divide the rectus lateralis muscle, and observe 

 the offset to it ; then cut off the end of the lateral mass of the atlas, and 

 remove the vertebral artery, so as to bring into view the nerve as it lies 

 on the first vertebra. 



The anterior primary branch of the first or sub-occipital nerve is slen- 

 der in size, and arises from the common trunk on the neural arch of the 

 atlas. From that origin it is directed forwards on the arch, beneath the 

 vertebral artery, to the inner side of the rectus lateralis : here it bends 

 down in front of the lateral mass of the bone, and forms a loop by uniting 

 with the second cervical nerve. As the nerve passes forwards it supplies 

 the rectus lateralis muscle, and branches connect the loop with the vagus, 

 hypoglossal, and sympathetic nerves. 



SYMPATHETIC NERVE. In the neck the sympathetic nerve consists, 

 on each side, of a gangliated cord, which lies close to the vertebral column, 

 and is continued into the thorax. On this part of the nerve ai'e three 

 ganglia : One near the skull, another on the neck of the first rib, and a 

 third somewhere between the two ; these are named respectively superior, 

 inferior, and middle ganglion. From the ganglia proceed connecting 

 branches with the spinal and most of the cervical cranial nerves; and 

 branches for distribution to viscera and bloodvessels. 



