A marriage bound together by commitments to exploit the other for filling one's own needs (and I fear that most marriages are built on such a basis) can legitimately be described as a "tic on a dog" relationship. Just as a hungry tic clamps on to a nourishing host in anticipation of a meal, so each partner unites with the other in the expectation of finding what his or her personal nature demands. The rather frustrating dilemma, of course, is that in such a marriage there are two tics and no dog!