Tonight Dr. Karl Menninger, cofounder (with his father and brother) of the famous Menninger Clinic in Topeka, Kans., will sketch a verbal self-portrait for the edification of some 225 invited guests, for the videotape collection of the National Portrait Gallery and for history.

Menninger's talk, which will be held in the Portrait Gallery's Great Hall, is part of a "Living Self-Portrait" lecture series launched early this year by Gallery director Marvin Salik. Previous speakers were labor leader Harry Bridges, acting teacher and actor Lee Strasberg and city planner Robert Moses.

"We are seeking verbal self-portraits, not for a 'hall of fame,' but for the unexpected person who is too busy making an important contribution to American life to spend much time advertising himself."

"We have not held it against our speakers if they have written books or given speeches," Salik said, "but we have weighted our choices in favor of deors. We want to record their own view of the ideas which have motivated and the events which have affected their lives and - indirectly - ours."

Sadik believes that portrait gallery should not rely on drawing, painting and sculpture alone to convey the persons who give history its personality. The new medium of sound-film, he says, should also be employed to gestures of individuals. "Imagine how much more deeply we would understand history if we could just capture the movements, speech and run off a videatape of George Washington talking."

Sadik readily admits that a self-portrait, painted or spoken, is not likely to give us the ultimate in historic truth and objectivity. The portraitist obviously decides in what light he wants to be seen.

Harry Bridges, who more than 30 years ago was accused of being a card-carrying Communist, and was to be deported as an "undesirable alien" (he was then an Australian citizen) turned a bright, revealing light on himself.

"As I have said many times in those various trails," Bridges said, "95 percent of the evidence against me was absolutely true. I never denied it. What help came along for the union, whether it was from Communists or anybody else, if we could use it, we took it. But one thing I didn't do, I didn't happen to be an official member of the Communist Party . . . It was no credit to me. I knew darn well that such things made me subject to deportation."

His point was: "We had a few things to change, and before we got through, we changed the darned thing."

Moses, who, for better or worse, also changed for a few things in the state and city of New York, chose to portray himself with deflecting, impressionistic and bright-colored anedotes and aphorisms. He talked and talked about Robert Oppenheimer and the Great Gatsby, opinion pools, the press, the 1972 Olympics, Edmund Wilson, and said that "Shelley tells us that life, like a dome of many-colored glass, stains the white radiance of eternity" which, he said, does little for youth trapped in slums.

His talk was like a Jackson Pollock painting.

Lee Strasberg, in turn, sketched a lot of affectionate detail into his portrait - of the American Theater. The persona of Strasberg came across nevertheless, simply because he is inextricably part of the American stage.

In order to add up to History, these living portraits, just as painted portraits, must be viewed along with a good many other things - the testimony of others, the official record, the interplay of event and personality.

The historian, furthermore, must probe; Sadik intends to experiment with filmed conversations and the kind of persistent questioning that the late Edward R. Murrow mastered in his "Person to Person" interviews.

But "objective" history, if there is such a thing, is not Sadik's goal. The National Portrait Gallery is not the National Archives.

The Portrait Gallery is now distilling its first four living portraits into a half-hour film. What it is attempting to do, is only to give us more of the stuff that history is made of.

The mental health students and experts who will listen to Karl Menninger and his learned concerns with medicine, psychiatry, mental health, prison reform, music, archeology, art, conversation, ecology and American Indians tonight are likely to get an intensive dose of it.