"Adam's Rib," that hilarious example of the special form of combat film known as the courtroom drama, makes its final showing tonight in the American Film Institute's five-week series on movie portrayals of the legal profession.

Viewers will be bickering for as long as the prints of Hepburn's and Tracy's numerous cinematic triumphs continue to circulate about which one of them is preeminent. AFI is on record, in its "Disorder in the Court" festival catalogue, to the effect that "Adam's Rib" is the greatest.

Who is to say? But in this film, the remarkable pair took on one of the classic cinematic forms-the tangle between two criminal lawyers. And in this case there was added the twist that they were husband and wife. The director was the redoubtable George Cukor, with the additional contribution in the category of supporting role, of Judy Holliday as the disarmingly sobbing defendant who had shot her husband. To top that, David Wayne, in a bit part, almost steals the show.

There seem to be strict limitations on the aspects of the legal profession that are translatable into motion pictures. The main one is that the subject must almost invariably be criminal law. That's where the drama is-and the romance.

It's not just Perry Mason, though he is well represented here in the mid-'30s Warners' productions. It started long before Raymond Burr's television version, with Warren William playing a Mason closer to Erle Stanley Gardner's creation than his television predecessor. All the characters are the same. The names are not changed to protect the innocent; just the players are changed.

To judge by this series, the most irresistible characterization of the lawyer on the film has been as a romantic figure. Admittedly, this is by the loose definition-the acerbic Hepburn seems more romantic in these liberated days than in 1949.

Tracy and Hepburn still seem to have been born yesterday. Their collaborations were dismissed at the time as light entertainment, but most of their films have actually grown with age.

The more conventionally romantic notion of the legal profession, as in Charles Laughton's grandiose, Edwardian (just on looks one would say Churchillian" barrister in Agatha Christie's "Witness for the Prosecution," by comparison seems remote in time, though eight years more recent. This is Laughton at his most expansive, both dramatically and physically. But, aside from his performance, the movie seems curiously dated. It's hard to believe, but Marlene Dietrich seems a pasteboard parody of herself.

Another movie, "Inherit the Wind," carried surprising visceral punch. Movies based on momentous events (in this case the Scopes trial) are usually pale reflections of history-but not when Tracy plays Darrow, Fredric March is Bryan and (in an unlikely casting) Gene Kelly portrays Mencken.

Like most lawyer movies, "Inherit the Wind" is only partially a film about the practice of the law. Were it not for its political and social depth, it would have little impact.

Surely there is a memorable movie in the average practice of law-in the tedium and in the riches. Perhaps Watergate is the best subject we have had for such a film, although the movies have so far only scratched the surface. CAPTION: Picture, Spencer Tracy, left, and Fredric March in "Inherit the Wind."