THE CIRCULATORY SYSTEM 35 



ventral carotid which passes laterally and over (ventral) 

 to the external carotid and enters the cartilage, later unit- 

 ing with the internal carotid within the brain cavity. 



The two most anterior efferent branchial arteries fuse 

 and just posterior to their union the vertebral artery arises 

 which enters the skull and is distributed to the brain and 

 the spinal cord. 



The efferent branchial arteries unite in pairs along the 

 median line and form the dorsal aorta which proceeds back- 

 wards into the pleuroperitoneal cavity. 



Deawing 18. Show the efferent branchial arteries and their vari- 

 ous branches. 



8. The Distribution of the Dorsal Aorta. 



Trace the dorsal aorta posteriorly by separating the 

 esophagus from the body wall on the left side. A sub- 

 clavian artery is given off to each side between the points 

 where the third and fourth pairs of efferent branchial 

 arteries enter the dorsal aorta. They go to the pectoral 

 fins. Trace the left subclavian. It gives off these arteries : 

 a posterior coronary artery, the distribution of which has 

 already been noted ; lateral arteries along the lateral body 

 wall; a^d a ventral abdominal artery which runs pos- 

 teriorly as a conspicuous colored artery on the ventral 

 wall; continuing as the brachial it is distributed to the 

 pectoral fin. 



A little posterior to the origin of the subclavian arteries 

 the dorsal aorta is completed. It then passes posteriorly 

 along the mid-dorsal line of the pleuroperitoneal cavity. 

 Find the following branches, doing the work on the left 

 side after turning the viscera over to the left side of the 

 body. 



a. Unpaired Visceral Branches. The coeliac is the first 



