A drawing used to be a record of a thing
For as long as there had been drawings, a drawing was a record of something seen or imagined and then composed. The artist chose a subject (a face, a tree, a saint, a vision) set it in a space, and laid down marks that described it. The hand was the obedient servant of a picture the mind had already chosen. The skill on show was depiction and control: how truly, how gracefully, the marks could be made to render the thing. Even the wildest pre-Surrealist drawing, the most visionary or the most violent, was still the hand executing a picture decided in advance. The marks served the subject.
Now the drawing records the hand itself
Masson turns that around. Here the drawing is a record of the unconscious hand itself, process over depiction. There is no prior subject. The line is laid down faster than judgment can intervene, and the “image” is whatever the viewer (and, after the fact, Masson) can find in the marks. The picture is no longer a window onto a chosen scene; it is a trace of an act, evidence of mark-making rather than a description of a thing. The inversion is the whole break: instead of the subject dictating the mark, the mark generates the subject. The line moves first, and the image is a guest that arrives in it.
That sounds like a small studio quirk and is in fact a hinge in the history of art. If the mark can come before the subject, then mark-making itself (the speed, the pressure, the unplanned path of the hand) can be the real content of a picture. That is the idea that runs forward, two decades later, into Abstract Expressionism and the dripped, poured, gestural canvases of the 1940s and ’50s, where the act of painting becomes the subject. The line from Masson to that moment is not invented after the fact: Jackson Pollockopenly admired Masson’s automatism, and the automatic line is one of the things he took from it. A small sheet of racing ink is one of the places that whole future opens.