32 GENERAL BIOLOGY 



From each of these large vessels arise a number of smaller 

 arteries; their origin should be determined, and. their dis- 

 tribution carefully followed. 



A. Carotid Arch. This arch divides into two arteries: 

 (a) External carotid or lingual which supplies blood to 



the tongue and muscles of the lower jaw. 

 (6) Internal carotid, which passes around the lower jaw 

 to the roof of the mouth, the orbit of the eye, and the 

 brain. 



At the junction o these two arteries is a swelling, 

 the carotid gland. 



B. Pulmo-cutaneous Arch. This, the posterior of the 

 three arches, divides into tw r o arteries : 



(a) The pulmonary extends to the lungs, in which it 

 divides into several smaller vessels. 



(6) The cutaneous extends anteriorly to the shoulder 

 w r here it passes dorsally, and, emerging behind the 

 ear, is distributed over the skin of the back and side. 



C. The middle arch, the systemic, extends dorsally, 

 passes around the esophagus, and the two sides of 

 the arch unite into a single vessel, the dorsal aorta, 

 which proceeds posteriorly along the spinal column. 

 From each side of the arch several arteries arise. 



(a) . The subclavian, a large artery which goes to the 

 shoulder, w-ill easily be found; it continues into the 

 arm where it is called the brachial. 



(6) The occipito-vertebral arises just anterior to the sub- 

 clavian, passes dorsally through the body wall and 

 divides into two arteries. Branches from this artery 

 may extend into the esophagus. 



(c) Laryngeal. Along the systemic arch between the 

 occipito-vertebral artery and the heart is a small 

 artery, the laryngeal, which goes to the trachea and 

 larynx. 



