The =left ventricle= (Ventriculus sinister) forms the left posterior
part of the ventricular mass. It is more regularly conical than the
right ventricle and its wall is much thicker except at the apex. It
forms all of the posterior border of the ventricular part and the apex
of the heart. Its base is largely continuous with the left atrium, with
which it communicates through the left atrio-ventricular opening, but in
front it opens into the aorta. The cavity usually appears smaller than
that of the right ventricle in the dead subject, on account of the
greater contraction of its wall. It is almost circular in cross-section.
[Illustration: