  We derive from the subleading contributions to the chiral three-nucleon force
(long-range terms, published in Phys.\,Rev.\,C\,77, 064004 (2008)) a
density-dependent two-nucleon interaction $V_\text{med}$ in isospin-symmetric,
spin-saturated nuclear matter. Following the division of the pertinent
3N-diagrams into two-pion exchange topology, two-pion-one-pion exchange
topology and ring topology, we evaluate for these all self-closings and
concatenations of nucleon-lines to an in-medium loop. The momentum and
$k_f$-dependent potentials associated with the isospin operators ($1$ and
$\vec\tau_1\!\cdot\!\vec\tau_2$) and five independent spin-structures are
expressed in terms of functions, which are either given in closed analytical
form or require at most one numerical integration. In the same way we treat the
$2\pi$-exchange 3N-force up to fourth order. Our results for $V_\text{med}$ are
most helpful to implement the long-range subleading chiral 3N-forces into
nuclear many-body calculations.
