The sinews

of animals have the following properties. For these
also the point of origin is the heart; for the heart has sinews within
itself in the largest of its three chambers, and the aorta is a
sinew-like vein; in fact, at its extremity it is actually a sinew, for
it is there no longer hollow, and is stretched like the sinews where
they terminate at the jointings of the bones. Be it remembered,
however, that the sinews do not proceed in unbroken sequence from
one point of origin, as do the blood-vessels.