Diagram to illustrate the action of the heart. Labels: aur, auricle (atrium); vent. ventricle; v, veins; a, aorta; m, mitral valve; s, semilunar valves. In A, auricle is seen contracting, ventricle dilated, mitral valve open, semilunar valves closed. In B, auricle is seen dilated, ventricle contracting, mitral valve closed, semilunar valves open.

Diagram of the Action of the Heart

Diagram to illustrate the action of the heart. Labels: aur, auricle (atrium); vent. ventricle; v, veins;…