The apex is to

a great extent fleshy and close in texture, and in the cavities of the
heart are sinews. As a rule the heart is situated in the middle of the
chest in animals that have a chest, and in man it is situated a little
to the left-hand side, leaning a little way from the division of the
breasts towards the left breast in the upper part of the chest.
The heart is not large, and in its general shape it is not
elongated; in fact, it is somewhat round in form: only, be it
remembered, it is sharp-pointed at the bottom. It has three
cavities, as has been said: the right-hand one the largest of the
three, the left-hand one the least, and the middle one intermediate in
size.