806 NERVOUS SYSTEM OF THE HORSE 
The left vagus nerve (Fig. 553) enters the thorax on the lateral or the ventral 
face of the cesophagus, crosses obliquely under the left brachial artery, and passes 
back on the lateral surface of that vessel in company with a large cardiac nerve.! 
Separating from the latter, the vagus continues backward on the left face of the 
Tigi mucho Nuchal fat 
Splenius Complexus tendon 
Rectus capitis 
dorsalis minor 
Rectus capitis 
dorsalis major 
Branch of occipital artery 
Complexus 
Spinal \& 
accessory 
nerve 
(dorsal 
branch) Spinal accessory 
Brachio- nerve (dorsal 
cephalicus branch) 
Vagus Rectus capitis 
ventralis major 
S theti } 
Sympathetic Jugular vein 
Carotid artery _— 
Thyro-laryngeal 
artery 
Anterior cervical 
lymph glands 
Ant. cervical 
lymph gland 
Thyroid gland 
——_—— 
External max- > 
illary vein 
Thyroid gland | 
Sterno-cephalicus 
7 : 
Sterno-thyroideus 
Omo-hyoideus and sterno-hyoideus 
Fic. 649.—Cross-section oF Neck OF Horse, PAsstne THROUGH PosTERIOR PART OF ATLAS. 
———— 
The head and neck were extended. 1, Dorsal arch of atlas; 2, dens of axis; 3, ligament of dens; 4, vertebral 
sinuses; 5, dura mater; 6, spinal cord; 7, vertebral artery; 8, wing of atlas; 9, atlanto-axial joint cavity; 10, 
esophagus; 11, //, recurrent nerves; 12, 12, ventral branches of spinal accessory nerves. By an oversight the obliquus 
cap. post. (above wing of atlas) is unmarked; also the parotid gland between the jugular and external maxillary vein. ( 
aorta, inclines to the upper surface of the left bronchus, and divides into dorsal and 
ventral branches. 
The dorsal and ventral branches unite with the corresponding branches of the 
opposite nerve, thus forming dorsal and ventral cesophageal trunks (Truncus 
1TIn some cases the left vagus passes back below the junction of the jugular veins and the 
termination of the left brachial vein. It then runs backward and somewhat dorsally across the 
left face of the anterior vena cava to reach its usual position. 
