  Let $T_{g,n}$ be a compact orientable topological surface of genus $g$ with
$n$ marked points and let $M(g,n)$ denote its mapping class group. We study the
action on the fundamental group of the surface induced by the
self-homeomorphisms of the mapping class group by describing completely the
case of positive genus. In order to do so, we use a presentation for the
mapping class group with generators the Humphries generators and compute their
images as elements of the outer automorphism group of the fundamental group,
since the action is defined only up to conjugation.
