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284 THE CIRCULATORY SYSTEM. 
then passes to about the level of the larynx without giving off 
branches; here it gives off the superior thyroid (c) on the 
ventral side and one or more muscular branches (e) on the 
dorsal side. One or two centimeters further craniad it gives 
oft on the dorsal side the internal carotid (g) and the occipital 
artery (/). The main artery now takes the name external 
carotid (72). 
Branches of the common carotid: 
Fic, 119,—CoMMON CAROTID ARTERY AND INTERNAL JUGULAR VEIN. 
a, common carotid artery; 4, internal jugular vein; -¢, superior thyroid artery; 2, 
' cervicalis ascendens artery; ¢, large muscular branches; /, occipital artery; g, in- 
ternal carotid; 2, branch to larynx; z, lingual artery; 7, external maxillary; 2, supe- 
rior labial; 7, inferior labial; 1, external carotid; ~, internal maxillary; 0, posterior 
auricular; Z, superficial temporal. 1, M. sternohyoideus; 2, M. sternothyreoideus; 
3, M. geniohyoideus; 4, M. genioglossus; 5, M. constrictor pharyngis medius; 6, M. 
constrictor pharyngis inferior; 7, M. longus capitis; 8, M. digastricus; 9, M. mas- 
seter; 10, M. scalenus; 11, M. levator scapulz (cut); 12, M. levator scapule ven- 
tralis (cut); 13, M. splenius; 14, trachea. 
1. A. thyreoidea ima.—The inferior thyroid is a small 
artery which arises either from the common carotid near its 
origin, or from the innominate before the origin of the carotid. 
It passes craniad on the trachea as far as the thyroid gland, 
giving branches to the trachea and cesophagus. 
2. A. thyreoidea superior (c).—The superior thyroid leaves 
the carotid opposite the thyroid cartilage and passes mediad 
and caudad, sending branches to the thyroid gland, and the 
