17

The heart has three cavities, and is situated above the lung at
the division of the windpipe, and is provided with a fatty and thick
membrane where it fastens on to the great vein and the aorta. It
lies with its tapering portion upon the aorta, and this portion is
similarly situated in relation to the chest in all animals that have a
chest. In all animals alike, in those that have a chest and in those
that have none, the apex of the heart points forwards, although this
fact might possibly escape notice by a change of position under
dissection. The rounded end of the heart is at the top.