Tick marks in graphs

Although this is probably a trivial concern, it nevertheless engendered many long arguments amongst my colleagues and myself in graduate school*.

When rendering a graph of one’s results, where ought the tick marks be placed: inside, outside, or both? I have always felt their proper place is inside the graph’s axes, purely upon aesthetic grounds. Perhaps someone here would have insight on the matter.

*This is a well known phenomenon. Often the most trivial of issues prompt the most passionate discussions amongst students.