THE THORAX. 



219 



auricle* through the auriculo-ventricular opening, to the right ventricle. This 

 opening is guarded by the right auriculo-ventricular valves. (3) Blood flows 

 from the right ventricle, by the pulmonary artery, to the lungs. This artery is 

 guarded by the pulmonary semilunar valves. (4) Blood flows from the lungs to 

 the left auricle of the heart by the pulmonary veins. These veins have no valves. 

 (5) Blood passes from the left auricle, by the left auriculo-ventricular opening, 



Left carotid 

 Innominate 



Left subclavian 



Right pulmonary artery 

 Duclus arteriosus 



Left pulmonary artery 



Pulmonary artery 

 Pulmonary semilunar valves 



LEFT AURICULAR APPENDIX 



Small papillary muscle connected 

 with septum 



(1) Columna caruea 



CHORD/E TENDINE* 



Anterior papillary 

 muscle 



Left coronary artery 



Vena cava inferior 

 ANTERIOR SEGMENT OF TRICUSPID VALVE 



RIGHT SEGMENT OF TRICUSPID VALVE 



SECTION OF VENTRICULAR WALL 



Vena cava inferior . 



lary muscle 



FIG. 154. ANTERIOR VIEW OF THE RIGHT CHAMBERS OF THE HEART, WITH THE GREAT VESSELS. 



(3) Posterior papil- (2) Columna oarnea 

 ile 



to the left ventricle. This opening is guarded by the left auriculo-ventricular 

 valves. (6) Blood passes from the left ventricle through the aorta to all vascu- 

 lar parts of the body. The aorta is guarded by the aortic semilunar valves. 

 Systole is a term by which contraction of the auricles and ventricles is desig- 

 nated ; diastole is its opposite. The one extrudes, the other draws in, blood. 



The Foetal Circulation. The lungs are essentially organs whose use in 

 distributing the blood for purification begins after birth. Before the product of 



