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.
Kao što svakoj stanici trebaju hranjive tvari za njen pogon, tako svaka stanica proizvodi otpad kao nusproizvod, i rješavanje tog otpada drugi je glavni problem koji svaki organ mora riješiti.