THE CIRCULATION OF THE BLOOD. 



265 



ventricular opening. From the apex of each papillary muscle there 

 are given off fine tendinous cords, the chorda tendinece, which become 

 attached above to the auriculo-ventricular valve. 



FIG. 112. THE RIGHT AURICLE AND VENTRICLE OPENED, AND A PART OF THEIR 

 RIGHT AND ANTERIOR WALLS REMOVED, so AS TO SHOW THEIR INTERIOR. 

 i i. Superior vena cava. 2. Inferior vena cava. 2'. Hepatic veins cut short. 

 3 Right auricle. 3'. Placed in the fossa ovalis, below which is the Eustachian 

 valve. 3 // . Is placed close to the aperture of the coronary vein. -\ \-. Placed 

 in the auriculo-ventricular groove, where a narrow portion of the adjacent walls 

 of the auricle and ventricle has been preserved. 4, 4. Cavity of the right ventri- 

 cle; the upper figure is immediately below the semilunar valves. 4'. Large 

 columna carnea or musculus papillaris. 5, 5', 5". Tricuspid valve. 6. Placed 

 in the interior of the pulmonary artery, a part of the anterior wall of that vessel 

 having been removed, and a narrow portion of it preserved at its commencement, 

 where the semilunar valves are attached. 7. Concavity of the aortic arch close 

 to the cord of the ductus arteriosus. 8. Ascending part or sinus of the arch cov- 

 ered at its commencement by the auricular appendix and pulmonary artery. 

 9. Placed between the innominate and left carotid arteries. 10. Appendix of 

 the left auricle, n, n. The outside of the left ventricle, the lower figure near 

 the apex. (Allen Thomson.) 



The left auricle, similar in general shape to the right, presents 

 posteriorly four openings, the terminations of the four final trunks 

 of the venous system of the lungs, the pulmonary veins. Below is 



