[Zope] how to access files outside the database

How can I access files that do not lie inside the Zope database. I need that feature because I have to write an image database where the images are stored in a common directory and only the filenames are stored in the RDBMS. If I address an image wit the <IMG...> tag zope searches in its internal object hierarchy. Is there any possibility? Thanks in advance Philipp Auersperg