THE ARTERIES. 443 



short, open into the posterior surface of the left 

 auricle. 



Turn the heart forwards : openthe left auricle: ivashout 

 the contents ; and pass a seeker along the pulmonary veins 

 into the lungs. 



C. The Arteries. 



1. The pulmonary artery is a single trunk, which arises 



from the anterior end of the right ventricle, close to 

 the ventral surface and a little to the left of the 

 median plane. It divides soon after its origin into 

 right and left pulmonary arteries. 



a. The left pulmonary artery is short, and passes 



direct to the left lung, which it enters in front 

 of the pulmonary vein, and ventral to the left 

 bronchus. 



b. The right pulmonary artery passes dorsal to the 



other arterial trunks, to enter the right lung in 

 front of the bronchus. 



2. The aorta arises from the base of the left ventricle, 



lying between the two auricles, and to the right 

 of, and slightly dorsal to, the pulmonary artery. It 

 gives off almost immediately the very large right 

 and left innominate arteries, and then continues its. 

 course as the dorsal aorta. 



a. The left innominate artery is a short wide artery, 

 which divides, after a course of about a quarter 

 of an inch, into two vessels of very unequal 

 size. 



i. The left carotid artery, which is much the 

 smaller of these two vessels, runs forwards 

 along the neck, lying close to its fellow of the 

 opposite side, in a groove along the ventral 

 surface of the vertebral column, 



About half an inch from its origin it gives 

 off the vertebral artery, which runs forwards 



