542 



BLOOD-VASCULAR SYSTEM OF THE HORSE 



two or three inches (ca. 5 to 7 cm.) in length, i)ut it may vary between one and 

 eight inches (ca. 2.5 to 20 cm.). 



The right common carotid artery passes ol)liqueIy from the ventral face of 

 the trachea to its right side. In this position it runs upward and forward and 

 divides at the crico-pharyngeus muscle and under the submaxillary gland into 

 external carotid, internal carotid, and occipital arteries. It is inclosed in a 

 fibrous sheath, and is accompanied dorsally by the vagus and sympathetic 



Fig. 431. — Vkssels .^nd Nkrves of Neck of Horse. 

 a, Mastoido-humeralis; t), .sterno-ceijhalicus; r, omo-hyoideus; d, .sterno-thyro-hyoideus; f, trachea; /.posi- 

 tion of cariniform cartilage; ;/, anterior superficial pectoral muscle; h, scalenus; i, intertransversales; k, insertion 

 of serratus cervicis; Z, origin of trapezius; m, rhomboideus; n, splenius; o, complexus; p, r/, trachelo-mastoideus; 

 p', q', tendons of same; r, longissimus; s, obliquus capitis posterior; t, wing of atlas; u, parotid gland; v, supra- 

 .spinatus; w, anterior deep pectoral; a:, spine of .scapula; ;/, prescapular lymph glands; 7, external maxillary vein; 

 3, 3, jugular vein; 4, carotid artery, exposed by drawing jugular vein aside; 5, 6, ascending and de.scending branches 

 of inferior cervical artery; 7, cephalic vein; 8, branches of superior or deep cervical artery; 9-14, ventral branches 

 of second to seventh cervical nerves; 15, branches of dorsal divisions of cervical nerves. (Ellenberger-Baum, 

 Top. Anat. d. Pferdes.) ■ 



nerves, ventrally by the recurrent nerve. At the last two cervical vertebrae 

 it is in contact superficially with the jugular vein, but further forward the 

 omo-hyoideus muscle intervenes between the artery and vein. Near its ter- 

 mination the artery becomes more deeply placed and is related externally to 

 the submaxillary and parotid glands, internally to the oesophagus. In some 

 cases it is in contact ventrally with the thyroid gland, especially when the 

 latter is larger than usual. 



