[Lilux-help] directory entries - how to get a close look

Hi guys, I'm currently preparing a course (for tomorrow, it's almost done). In this course, I explain the classic UNIX filesystem (stuff like inodes etc.). Now, I'd like to show the students "live" what the directory entries look like - they are files containing a table with the relation inode number to filename. IIRC it used to be that you could simply open such a file and look at the raw contents (hexdump or whatever) - this though doesn't work any more, if I try to open a directory directly with vi, cat, less, hexdump, xxd, od, it doesn't work. Does someone have an idea how I could get a close look at such a directory entry? Maybe how to directly access an inode, without going through the filename? [inode numbers can be had by using ls -i, I'd have liked to directly look at the directory entry itself]. I asked around the office, the usual suspects have as little ideas as I do... Greets & thanks in advance, Eric