CIRCULATION OF THE BLOOD. 



131 



I 



ous fine threads, the chorda tendinece, which are the tendons 

 of the small papillary muscles springing from the walls of the 

 ventricles. 



The Semilunar Valves. At the openings of the pulmonary artery 

 and the aorta are found three cup-shaped or semilunar valves, the 

 free edges of which are directed 

 away from the interior of the 

 heart. The anatomic arrangement of 

 the valves is such that upon their 

 closure regurgitation of the blood is 

 prevented. 



The Course of the Blood through 

 the Heart. Reference to figure 17 

 will make it clear that there is a 

 pathway for the blood between the 

 venae cavse on the right side and 

 the aorta on the left side by way 

 of the right side of the heart, the 

 cardio-pulmonary vessels and the left 

 side of the heart. 



The venous blood flowing towards 

 the heart is emptied by the su- 

 perior and inferior venae cavae into 

 the right auricle from which it 

 passes through the auriculoventric- 

 ular opening into the right ven- 

 tricle; thence into and through the 

 pulmonary artery and its branches 

 to the pulmonary capillaries where 

 it is arterialized, *. e. } yields up its 

 carbon dioxid and takes on a fresh 

 supply of oxygen and is changed in 

 color from dark blue to scarlet red. 

 The arterialized blood flowing to- 

 wards the heart is emptied by the 

 pulmonary veins into the left au- 

 ricle from which it passes through 

 the auriculoventricular opening into 

 the left ventricle; thence into the 



FIG. 17. SCHEME OF THE CIR- 

 CULATION. (Landois.) 



a. Right, b. left, auricle. A. 

 Right, B. left ventricle, i. 

 Pulmonary artery. 2. Aorta. 

 1. Area of pulmonary, K. area 

 of systemic, circulations, o. 

 The superior vena cava. G. 

 Area supplying the inferior 

 vena cava, u. d, d. Intes- 

 tine, m. Mesenteric artery, 

 q. Portal vein. L. Liver, 

 h. Hepatic vein. 



