Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/76

62 to send blood throughout the body than through the pulmonary circulation. Observe the trabeculae carneae on the inner surface of the left ventricle's wall. The aortic orifice, surrounded by the aortic valve, is the opening into the aorta. Part of the valve may have been torn in opening the ventricle. The mitral, or bicuspid valve surrounds the mitral orifice, through which blood passes from the left atrium to the left ventricle. Note the chordae tendineae extending from this valve also to the ventricular wall. The ventricular septum is the muscular partition between the cavities of the right and left ventricles. Open the left atrium, wash out the coagulated blood, and find the orifices of the pulmonary veins. How many openings are there? View the partition between the atria (the atrial septum) by strong transmitted light. The fossa ovalis is the translucent area which will be seen in this septum. Ask the instructor to explain its significance.

Exercise XVI. Make a diagrammatic sketch of the internal anatomy of the heart.

The arteries and veins posterior to the heart will be studied after the examination of the respiratory, digestive, and urinogenital systems.