142 



OUR BODIES AND HOW WE LIVE 



those of the auricles, and those of the left ventricle are 

 much stouter than those of the right ventricle. 



The right auricle opens into the right ventricle, and the 

 left auricle into the left ventricle ; but there is no connec- 

 tion between the right 

 and left cavities of the 

 heart. 



200. The Valves of 

 the Heart. The open- 

 ings between the aur- 

 icles and ventricles are 

 guarded by flaps of mem- 

 brane, or little swing 

 doors, called valves. 



These valve flaps may 

 be roughly compared to 

 folding doors or gates, 

 which, by opening only 

 one way, allow the blood 

 to flow in that direction 

 and prevent its flowing 

 in any other. 



The valve on the right 

 side of the heart is called 



FIG. 87. Posterior View of the Heart. 

 L.A., left auricle; R.A., right auricle; L.V., left 



ventricle; R.V., right ventricle; ,4, opening thg three-pointed, Or 

 of the inferior vena cava ; B, superior vena r 



cava; C, right pulmonary veins; D, left pul- tlicUSpid, Valve. 



The valve on the left 

 looks somewhat like a 

 bishop's miter ; hence it 

 is called the mitral valve. 

 These valves fall back to let the blood flow from the 

 auricles into the ventricles, but float up with the blood so 



monary veins ; , aorta ; F, left branch of 

 pulmonary artery ; G, great cardiac vein ; 

 H, middle cardiac vein. The cardiac lym- 

 phatics which follow the course of the car- 

 diac veins are also shown. 



