Each of the four cavities of the heart is capable of containing about two ounces of blood. The ventricles are supposed to contain a little more than the auricles. The right auricle and right ventricle are somewhat larger in their capacities than the cavities of the left side; anatomists are not, however, fully agreed upon this point.

Fig. 5. This figure represents the Interior of Left Ventricle and Aorta laid open by dissecting from before backwards.

A Aorta. B. C, Left Pulmonary Veins. D, D, Orifices of the Coronary Arteries. E, Interior of Lett Auricle. F, F, Semilunar Valves of the Aorta. G, Anterior Surface of the Valvular Septum of Lieutaud, and passage from the Cavity of the Ventricle into the Aorta. H, Attachment of Chordae Teudineae to the Mitral Valve. I. Left Auriculo-Ventricular Opening. J, Carneae Columnae. K. Lower Portion of the Cavity. L, Right Auricular Appendix. M, Carneae Columnae. N, Right Ven-tricle. O, Septum Ventriculorum dissected, and cut surface shown.

The weight of the heart is estimated at about from eight to ten ounces.