Exchange effects andn-body forces in nuclear matter

The $n$-pion-exchange ($n+1\mathrm{}$)-body force is written explicitly in coordinate space and separated into its central and tensor parts. Exchanges of the spectator nucleons are shown to cause large cancellations. The ratio of $n$-body forces to ($n+1\mathrm{}$)-body forces is estimated and compared with recent three- and four-body calculations.