370 ARTERIES. 



PLAN OF THE BELATIOXS OF THE COMMON CAROTID ARTERY. 



In front. 



Integument and fascia. Omo-hyoid. 



Platysma. Descendens noni nerve. 



Sterno-mastoid. Sterno-mastoid artery. 



Sterno-hyoid. Thyroid, lingual, and facial veins. 



Sterno-thyroid. Anterior jugular vein. 



Externally. ^ >. Internally. 



Internal jugular vein. / \ Trachea. 



Pneumogastric nerve. / Common \ Thyroid gland. 



Recurrent laryngeal nerve. 



Inferior thyroid artery. 



Larynx. 



Pharynx. 



Behind. 



Longus colli. Sympathetic nerve. 



Rectus anticus major. Inferior thyroid artery. 



Recurrent laryngeal nerve. 



Peculiarities as to Origin. The right common carotid may arise above or below its usual 

 point (the upper border of the sterno-clavicular articulation). This variation occurs in one out 

 of about eight cases and a half, and is more frequently above than below the point stated ; or its 

 origin may be transferred to the arch of the aorta, or it may arise in conjunction with the left 

 carotid. The left common carotid varies more frequently in its origin than the right. In the 

 majority of cases it arises with the innominate artery, or, where the innominate artery was ab- 

 sent, the two carotids arose usually by a single trunk. This vessel has a tendency towards the 

 right side of the arch, occasionally being the first branch given off from the transverse portion. 

 It rarely joins with the left subclavian, except in cases of transposition of the arch. 



Point of Division. The most important peculiarities of this vessel, in a surgical point of 

 view, relate to its place of division in the neck. In the majority of cases, this occurs higher than 

 usual, the artery dividing into two branches opposite the hyoid bone, or even higher ; more rarely, 

 it occurs below its usual place, opposite the middle of the larynx, or the lower border of the cri- 

 coid cartilage ; and one case is related by Morgagni, where this vessel, only an inch and a half 

 in length, divided at the root of the neck. Very rarely, the common carotid ascends in the neck 

 without any subdivision, the internal carotid being wanting ; and in two cases the common 

 carotid has been found to be absent, the external and internal carotids arising directly from the 

 arch of the aorta. This peculiarity existed on both sides in one subject, on one side in another. 



Occasional Branches. The common carotid usually gives off no branches, but it occasionally 

 gives origin to the superior thyroid, or a laryngeal branch, the inferior thyroid, or, more rarely, 

 the vertebral artery. 



Surgical Anatomy. The operation of tying the common carotid artery may be necessary in 

 a wound of that vessel or its branches, in an aneurism, or in a case of pulsating tumor of the orbit 

 or skull. If the wound involves the trunk of the common carotid, it will be necessary to tie the 

 artery above and below the wounded part. If, however, one of the branches of that vessel is 

 wounded, or has an aneurismal tumor connected with it, a ligature maybe applied to any part of 

 it, excepting its origin and termination. When the case is such as to allow of a choice being 

 made, the lower part of the carotid should never be selected as the spot upon which a ligature 

 should be placed, for not only is the artery in this situation placed very deeply in the neck, but 

 it is covered by three layers of muscles, and on the left side of the jugular vein, in the great ma- 

 jority of cases, passes obliquely in front of it. Neither should the upper end be selected, for here 

 the superior thyroid, lingual, and facial veins would give rise to very considerable difficulty in the 

 application of a ligature. The point most favorable for the operation is opposite the lower part 

 of the larynx, and here a ligature may be applied on the vessel, either above or below the point 

 where it is crossed by the Omo-hyoid muscle. In the former situation the artery is most acces- 

 sible, and it may be tied there in cases of wounds, or aneurism of any of the large branches of the 

 carotid; whilst in cases of aneurism of the upper part of the carotid, that part of the vessel may 

 be selected which is below the Omo-hyoid. It occasionally happens that the carotid artery bifur- 

 cates below its usual position : if the artery be exposed at its point of bifurcation, both divisions 

 of the vessel should be tied near their origin, in preference to tying the trunk of the artery near 

 its termination; and if, in consequence of the entire absence of the common carotid, or from its 

 early division, two arteries, the external and internal carotids, are met with, the ligature should 

 be placed on that vessel which is found on compression to be connected with the disease. 



