446 ARTERIES. 



interposed ; higher up, with the larynx and pharynx. On its outer side are 

 placed the internal jugular vein and pneumogastric nerve. 



At the lower part of the neck, the internal jugular vein on the right side 

 diverges from the artery, but on the left side it approaches it, and often crosses 

 its lower part. This is an important fact to bear in mind during the perform- 

 ance of any operation on the lower part of the left common carotid artery. 



PLAN OF THE RELATIONS OF THE COMMON CAROTID ARTERY. 



Infront. 



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. 



. . Internally. 



f N, Trachea. 



Externally. \ Thyroid gland. 



Internal jugular vein. Sid Recurrent laryngeal nerve. 



Pneumogastric nerve. V / 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 the origin is more frequently above than below the usual 

 point ; or the artery may arise as a separate branch from the arch of the aorta, or in conjunction 

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

 right. In the majority of abnormal cases it arises with the innominate artery, or if the innomi- 

 nate artery is absent, the two carotids arise usually by a single trunk. The left carotid has a 

 tendency towards the right side of the arch of the aorta, being occasionally the first branch 

 given off from the transverse portion. It rarely joins with the left subclavian, except in cases 

 of transposition of the arch. 



Peculiarities as to Point of Division. The most important peculiarities of this vessel, in a 

 Burgical point of view, relate to its place of division in the neck. In the majority of abnormal 

 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 body of the cricoid cartilage ; and one case is related by Morgagni, where 

 the common carotid, 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 the other. 



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. But in cases of aneurism, or where one of the 

 branches of the common carotid is wounded in an inaccessible situation, it may be judged neces- 

 sary to tie the trunk. In such cases, the whole of the artery is accessible, and any part may be 

 tiea, except close to either end. 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 to place a ligature, 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 the jugular vein, in the great majority of cases, passes 

 obliquely in front of it. Neither should the upper end lie 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 accessible, and it 

 may be tied there in cases of wounds, or aneurism of any of the large branches of the carotid ; 



