THE VASCULAR SYSTEM 57 



(3) Deep ariery of the arm. Leaving the distal end of 

 the axillary artery, it sends branches to muscles of the 

 upper arm (triceps), then proceeds distally along a spiral 

 course, and finally sends branches down the anterior and 

 lateral surfaces of the fore arm. 



(4) The hrachial artery, the continuation of the axillary, 

 passes through the arm pit region, thence down the medial 

 surface of the upper arm in company with the large 

 nerves in this part of the arm. It lies throughout its 

 length close to the posterior edge of the biceps brachii 

 muscle. The artery provides branches for the muscles of 

 the elbow region, but the main trunk passes down the 

 forearm. 



The second large arterial trunk leaving the aortic arch 

 is the left common carotid artery. It originates from the 

 aortic arch between the innominate artery and the origin 

 of the left subclavian, and passes forward lateral to the 

 trachea as far as the anterior end of the neck, where it 

 splits into the external and internal carotid arteries. 



The internal carotid artery proceeds anterodorsally from 

 its origin and divides into two branches immediately pos- 

 terior to the tympanic bulla. The dorsal branch of the two 

 enters the tympanic bulla through the posterior lacerated 

 foramen, which is situated on the median surface of the 

 bulla immediately in front of the jugular process. The 

 ventral branch enters the cranium by way of the carotid 

 foramen. 



The external carotid artery gives off the following 

 branches. 



(1) The occipital artery courses anterodorsally, from its 

 origin immediately anterior to the internal carotid artery, 

 passes around the median surface of the jugular process, 

 thence dorsally to the dorsal musculature of the neck. 



(2) The superior thyroid artery runs ventrally from its 



