  Quiver mutation plays a crucial role in the definition of cluster algebras by
Fomin and Zelevinsky. It induces an equivalence relation on the set of all
quivers without loops and two-cycles. A quiver is called mutation-acyclic if it
is mutation-equivalent to an acyclic quiver. This note gives a proof that full
subquivers of mutation-acyclic quivers are mutation-acyclic.
