282 COMMON CAROTID ARTERIES. 



mogastric nerve and cardiac nerves ; externally ', with the right vena inno- 

 ininata and pleura ; and internally, with the origin of the left carotid. 



Plan of the Relations of the Jlrieria Innominata. 



In Front. 



Left vena innominata, 

 Tliymus gland, 

 Sterno-thyroid, 

 Sterno-hyoid. 



Right Side. 



Right vena innominata, 

 Pleura. 



Arteria innominata. 



Left Side. 

 Left carotid. 



Behind. 

 Trachea, 



Pneumogastric nerve, 

 Cardiac nerves. 



The arteria innominata occasionally gives off a small branch, which 

 ascends along the middle of the trachea to the thyroid gland. This branch 

 was described by Neubauer, and Dr. Harrison names it the middle thyroid 

 artery. A knowledge of its existence is important in performing the ope- 

 ration of tracheotomy. 



COMMON CAROTID ARTERIES. 



The common carotid arteries (xo^a, the head,) arise, the right from the 

 bifurcation of the arteria innominata opposite the right sterno-clavicular 

 articulation, the left from the arch of the aorta. It follows, therefore, that 

 the right carotid is shorter than the left ; it is also more anterior ; and, in 

 consequence of proceeding from a branch instead of from the main trunk, 

 it is larger than its fellow. 



The Right common carotid artery (fig. 145, No. 5) ascends the neck 

 perpendicularly, from the right sterno-clavicular articulation to a level with 

 the upper border of the thyroid cartilage, where it divides into the external 

 and internal carotid. 



The Left common carotid (fig. 145, No. 11) passes somewhat obliquely 

 outwards from the arch of the aorta to the side of the neck, and thence 

 upwards to a level with the upper border of the thyroid cartilage, where it 

 divides like the right common carotid into the external and internal carotid. 



Relations. The right common carotid rests, first, upon the longus colli 

 muscle, then upon the rectus anticus major, the sympathetic nerve being 

 interposed. The inferior thyroid artery and recurrent laryngeal nerve 



Eass behind it at its lower part. To its inner side is the tracrtea, recurrent 

 iryngeal nerve, and larynx ; to its outer side, and enclosed in the same 

 sheath, the jugular vein and pneumogastric nerve ; and in front, the sterno- 

 thyroid, sterno-hyoid, sterno-mastoid, omo-hyoid, and platysma muscles, 

 and the descendens noni nerve. The left common carotid, in addition to 

 the relations just enumerated, which are common to both, is crossed neai 

 its commencement by the left vena innominata ; it lies upon the trachea ; 

 then gets to its side, and is in relation with the oesophagus and thoracic 

 duct : to facilitate the study of these relations, I have arranged them in a 

 tabular form. 



