R for Mac OS X Search in Help

Hi:
A small query about R for Mac on OSX:
when looking at the help system screens, it does not seem to be possible 
to search within them.
For example, when looking at a long help page (e.g. for par) I often 
want to search for a particular
parameter. But I don't see how. I just have to scroll and search by eye.
Is there a better way?
Thanks
Robt