Opening structures distributed inside scheme/misc/

How do I open structures distributed inside scheme/misc/, like
scheme/misc/pipe.scm?

,open doesn't work, as it can't find the structure.

I see that the procedures inside 'pipe.scm' are exported as a structure
called 'call-with-mumble-pipes', but ',open' can't find it neither.

Apparently I'm only able to open structures listed inside
scheme/packages.scm.

-- 
Diogo F. S. Ramos