First of all

, then, upwards from the heart there stretches a
part of the great blood-vessel towards the lung and the attachment
of the aorta, a part consisting of a large undivided vessel. But there
split off from it two parts; one towards the lung and the other
towards the backbone and the last vertebra of the neck.

The vessel, then, that extends to the lung, as the lung itself
is duplicate, divides at first into two; and then extends along by
every pipe and every perforation, greater along the greater ones,
lesser along the less, so continuously that it is impossible to
discern a single part wherein there is not perforation and vein; for
the extremities are indistinguishable from their minuteness, and in
point of fact the whole lung appears to be filled with blood.