<p>
The Carolina Panthers signed former Cincinnati Bengals safety Tom Nelson.</p> <p>
Rookie safety Tre Boston is on the physically unable to perform list.</p> <p>
Nelson, 27, has played in 24 career games.</p> <p>
He recorded 25 tackles in a dozen games with three starts for the Bengals in 2009.</p> <p>
Nelson has also played for the Philadelphia Eagles and Chicago Bears.</p> <p>
Follow me on Twitter: <a href="http://www.twitter.com/RavensInsider">@RavensInsider</a></p> <p>
Aaron Wilson covers the Ravens for The Baltimore Sun</p>