Now, just as every cell requires nutrients to fuel it, every cell also produces waste as a byproduct, and the clearance of that waste is the second basic problem that each organ has to solve.
Așa cum fiecare celulă are nevoie de nutrienți s-o alimenteze, fiecare celulă produce deșeuri ca produs secundar, iar eliminarea deșeurilor e a doua problemă de bază pe care fiecare organ trebuie s-o rezolve.