Of the other

internal organs the heart alone contains blood.
And the lung has blood not in itself but in its veins, but the heart
has blood in itself; for in each of its three cavities it has blood,
but the thinnest blood is what it has in its central cavity.

Under the lung comes the thoracic diaphragm or midriff,
attached to the ribs, the hypochondria and the backbone, with a thin
membrane in the middle of it. It has veins running through it; and the
diaphragm in the case of man is thicker in proportion to the size of
his frame than in other animals.