Pope - can a pope retire?

[Ticklesome]

It seems harsh to keep the present Pontiff in harness when he is so frail and ill. Perhaps he does want to carry on but even so it is a sad situation.
Do you know of a case when a Pope retired from his duties due to illness and if so, who fills in for him. All right, no-one could take his place really but you get what I mean.
And if it hasn't ever happened, don't you think they should make contingency plans after so many centuries.

[Revtim]

Yes.

http://slate.msn.com/id/1007125/

[Ticklesome]

Thanks Revtim. Looks as if some of the precedents were dubious, so this Pope might not find the concept of abdication an honourable one.