“The blood, the fountain whence the spirits flow,
The generous stream that waters every part,
And motion, vigour, and warm life conveys
To every particle that moves or lives;
This vital fluid, through unnumbered tubes
Poured by the heart, and to the heart again
Refunded; scourged for ever round and round;
Enraged with heat and toil, at last forgets
Its balmy nature; virulent and thin
It grows; and now, but that a thousand gates
Are open to its flight, it would destroy
The parts it cherished and repaired before.
Besides, the flexible and tender tubes
Melt in the mildest, most nectareous tide
That ripening Nature rolls; as in the stream
Its crumbling banks; but what the vital force
Of plastic fluids hourly batters down,
That very force, those plastic particles
Rebuild: so mutable the state of man.
For this the watchful appetite was given,
Daily with fresh materials to repair
This unavoidable expense of life,
This necessary waste of flesh and blood.
Hence the concoctive powers, with various art,
Subdue the cruder aliments to chyle;
The chyle to blood; the foamy purple tide
To liquors, which through finer arteries
To different parts their winding course pursue;
To try new changes, and new forms put on,
Or for the public, or some private use.”