ARTERIES. 



whole system, are called arteries. The first-named, the rami- 

 fications of the pulmonary artery, contain the dark blood 

 which is carried to the lungs to be oxygenized by contact 

 with the air. It is on the contrary red blood which runs in 

 the aorta, the original trunk of all the arteries distributed 



A- 1 



Fig. 27. -Transverse section of the heart. 



A. Right ventricle. 



B. Left ventricle. 

 C Right auricle. 



D. Left auricle. 



E. Right auricula-ventricular orifice 



and tricuspid valve. 



F. Left auriculo-ventriciilar orifice 



and mitral valve. 



G. Origin of tJie pulmonary artery 



and sigmoid valves. 

 H. Origin of tJie aorta, and valves. 

 I. Orifice of inferior vena cava. 

 K. Superior vena cava. 

 L, L. Orifice of the pulmonary veins. 



through the body. There are two classes of arteries, one 

 pertaining to the pulmonary system or lesser circulation, and 

 the other to the aortic or general circulation. We will first 

 consider the last-named. 



The ancient anatomists, finding the arteries empty after 

 death, believed that they were designed to contain air, and 

 from this circumstance they derive their name (aer, air, and 



