758 THE VASCULAR SYSTEM. 
The right common carotid artery, as already stated, differs as regards origin 
from the left common carotid. In length and general position it corresponds with 
the cervical portion of the left common carotid, and its relations also are ver 
similar. Such differences as exist may be briefly summarised as follows :—The 
internal jugular vein on both sides lies external to the artery; on the left side it 
runs well in front of the carotid artery in the lower part of the neck, whilst on the 
right side the vein is separated from the outer surface of the artery at its lower end 
by a well-marked interval in which the vagus nerve appears. The thoracic duct 
does not come into relation with the right common carotid, and there is also a 
Anterior superficial temporal artery 
Transverse facial artery 
Posterior superficial 
temporal artery 
Angular artery 
Lateral nasal 
artery 
Superficial temporal 
artery 
Internal maxillary 
jartery Septal artery 
Superior 
coronary artery 
~Inferior 
coronary artery 
_Inferior labial 
artery 
Posterior auricular 
artery 
Posterior belly of 
digastric muscle 
Occipital artery 
Submental 
artery 
Facial artery 
Internal carotid artery — 
External carotid artery “Li 
ternal carotid artery Lingual artery 
* Superior thyroid artery 
“ae j« ‘a ~ = i 
Brachial plexus Common carotid artery 
Transverse cervical artery 
Subclavian artery Inferior thyroid artery 
Suprascapular artery 
_—— Subcelavian artery 
— Sterno-mastoid muscle 
Fic. 554.—THE CarotTip AND SUBCLAVIAN ARTERIES AND THEIR BRANCHES. 
difference in the relations of the recurrent laryngeal nerves to the arteries on the 
two sides. On the left side the nerve crosses behind the mediastinal part of the 
left artery, and lies internal to its cervical part, whilst the corresponding nerve on 
the right side passes behind the lower part of the carotid artery in the neck to reach 
its imner side. 
THE EXTERNAL CAROTID ARTERY. 
The external carotid artery (a. earotis externa, Fig. 555) is the smaller of the two 
terminal branches of the common carotid ; its length is about two and a half inches 
