Fig. 164.—Heart of Sheep, in position between the lungs. R.A., appendage of right auricle; L.A., appendage of left auricle; R.V., right ventricle; L.V., left ventricle; S.V.C., I.V.C., great veins from the system generally; P.A., artery to lungs; Ao., aorta; A´o´., branch of aorta; L., lung; Tr., windpipe, leading to lungs; 2, 3, 4, fat.
Fig. 165.—The orifices of the heart seen from above, the auricles and great vessels being cut away. PA, valves at base of artery to lungs; Ao, valves at base of aorta; R.A.V., orifice between right auricle and ventricle, with its valves l.v. 1, l.v. 2, and l.v. 3; L.A.V., orifice between left auricle and ventricle, with its valves m.v. 1 and m.v. 2.
Fig. 166.—Diagrammatic sections of veins with valves. In the upper figure the blood is supposed to be flowing in the direction of the arrow, towards the heart; in the lower, back towards the capillaries.