688 



NERVOUS SYSTEM OF THE HORSE 



internal carotid artery and crosses the inner face of the origin of the occipital 

 artery. Here it is joined l^y the cervical trunk of the sympathetic, and the two 

 nerves continue along the dorsal aspect of the common carotid artery in a common 

 sheath (Fig. 433). At the root of the neck the vagus separates from the svm- 



Lig. 'riuclid 

 Splenius 



Nuchal fat 



Branch oj occipital artery 

 Complexus 



( 'omplexus tendon 

 T ntertransversalis 



Rectus capitis 

 posterior major 



Spinal 



accessory 



7ierve 



(dorsal 



branch) 



Mastoido- 



humeralis 



Vagus 



Sympathetic 

 Carotid artery _ 



Ant. cervical 

 lymph gland 



Thyroid gland 



External max- 

 illary vein 



Sterno-cephalicus 

 Omo-hyoideus and sterno-hyoideus 



Spinal accessary 

 nerve (dorsal 

 branch) 

 Rectus capitis ante- 

 rior major 



Jugular vein 



TJiyro-laryngeal 

 artery 



Anterior cervical 

 lynipJi glands 



Thyroid gland 



Stern o-th yroideus 



Fig. 517. — Cross-section of Ni^ck of Horse, Pa.ssing throuoh Posterior Part of Atlas. 

 The head and neck were extended. /, Dorsal arch of atla.s; 2, odontoid process; -3, odontoid hgament; 

 4, vertebral sinuses; 5, dura mater; 6, spinal cord; 7. vertebral artery; 8, wing of atlas; 9, atlanto-axial joint 

 cavity; /O, oesophagus; ii, H, recurrent nerves; 12, 12, ventral branches of spinal accessory nerves. By an 

 oversight the obliquus cap. post, (above wing of atlas) is unmarked. 



pathetic, and from this point backward the relations of the right and left vagi differ 

 somewhat and must be described separately. 



The right vagus (Fig. 429) enters the thorax in the angle of divergence of the 

 right brachial art(n-v and the truncus bicaroticus. It then passes ])ackward and 

 slightly upward, crossing obliquely the outer surface of the brachiocephalic artery 

 and the right face of the trachea. Reaching the dorsal surface of the latter near 

 the bifurcation, it divides into dorsal and ventral branches. 



