42 PHYSIOLOGY. 



The Valves of the Heart. Between the auricles and 

 the ventricles are curtain-like valves, whose upper edges 

 are attached to the inner surface of the walls at the upper 

 margin of the ventricle. These flaps are somewhat tri- 

 angular, and have strong, white, tendinous cords extending 

 from their edges and under surfaces to the walls of the 

 ventricle below. In the right half of the heart there are 

 three flaps, and this valve is called the tricuspid valve. In 

 the left side there are two flaps, which, together, constitute 

 the mitral valve. As these valves are between the auricles 

 and the ventricles, they are called the auriculo-ventricular 

 valves, or, for short, the aur-vent valves. 



The Semilunar Valves. From the base of the right 

 ventricle arises the pulmonary artery. Within its base, 

 just as it leaves the ventricle, are three pocket-like valves, 

 like " patch-pockets." They are in a circle, with their edges 

 touching, and thus surround the opening, with their mouths 

 opening away from the heart. A similar set of valves are 

 within the base of the aorta, which arises from the left 

 ventricle. Both these sets of valves are called ventriculo- 

 arterial, or, for short, vent-art valves. 



The Blood Tubes connecting the Heart with Other 

 Organs. The aorta (the largest artery in the body) 

 arises from the base of the left ventricle, and supplies 

 with blood every organ of the body except the lungs. 

 The pulmonary artery springs from the base of the right 

 ventricle and sends blood to the right and left lungs. 

 Two large veins enter the right auricle, the precaval vein 

 from the anterior regions of the body and the postcaval 

 vein which brings blood from all the organs of the poste- 

 rior portions of the body. The pulmonary veins return the 

 blood from the lungs to the left auricle, two from each lung. 



