The work of “outsider” artist Martín Ramírez (1895–1963) throbs with the sense of being trapped inside — trapped by circumstance, trapped in his head. Being an untrained artist who worked for his own diversion beyond the mainstream of the art establishment was not his problem. Ramírez was a true outsider, an alien — presumably illegal — in an often inhospitable country.

Born in Los Altos de Jalisco, Mexico, Ramírez was a landowning farmer with a wife and four children who migrated north to America in order to find temporary employment in 1925. Letters he sent home sometimes contained sketches in the margins. In 1931, homeless during the Great Depression, he was arrested in northern California. Destitute and unable to speak English, he was committed to the Stockton State Hospital. A year later, he was diagnosed as suffering from catatonic schizophrenia; he spent the remainder of his life confined to state mental institutions.

Ramírez was transferred to the DeWitt State Hospital in Auburn, Calif., in 1948. While there he began to draw in earnest, eventually producing hundreds of drawings and collages. More than 90 of these are on view in a curious and engrossing show at the American Folk Art Museum through April 29.

Although Ramírez’s works on paper have been appreciated since the 1950s and have been exhibited before, they were initially understood primarily under the rubric of “art of the insane.” One early show, from 1954, was titled “The Art of a Schizophrene.”

The current exhibition, and the excellent catalog that accompanies it, focuses on the artistic merit of his work, while providing much new scholarly research into Ramírez’s biography. It doesn’t explicitly question his diagnosis, but it does add details that seem to contradict previous assumptions about the artist — for instance, he spoke to certain people, though he was thought by his doctors to be mute.

Ramírez’s drawings speak eloquently of his ingenuity, wry humor, and exquisite eye for design. They return obsessively to the same motifs: a horse and rider, trains running through tunnels, Madonnas, skeletons, and stags, among others. But it is his cramped, though pleasing and decorative, use of pictorial space that sets the artist’s vision apart.

Take, for instance, the horse-and-rider drawings. He locates the figures centrally, on a psychedelic stage. Angled brick-tile shapes often define the foreground and proscenium. At his most decorative, slanting lines leading from the hats of tiny cowboys in the foreground zigzag with lines in the stage floor slanting the opposite direction. Slats for the walls and angled beam-like lines on the ceiling reinforce a quality of recession. Dipping curves form the curtains. A number of these drawings further decorative motifs, such as lozenge shapes across the sheets’ upper edges.

Within the boxy stage, a single pistol-wielding, sombrero-wearing cowboy with a gun belt invariably sits atop a steed with a rearing head. He generally twists backward in his saddle, as though pointing his gun into Ramírez’s ranchero past back home in Mexico. One might call him the Sad-Eyed Cowboy for the pathos in the caret-like glyph that often stands for the eyes.

Knowing the artist’s history, it is, of course, the confining spaces that activate the pathos of these drawings, even when no human figure is evident. The trains, for example, run not just from one impossibly tight tunnel to another: Between the tunnels, their tracks also lead them through lowering and indeterminate visionary spaces. Again patterns of lines and loops and repeated parabolas bear down, at once enlivening the pictures and mocking the trains as figures of escape.

All these images have an ornamental, rather than naturalistic, appeal. A train, for instance, might run horizontally across the top of a sheet and then vertically down its length, as in a wallpaper pattern. Yet there is nothing decorative or precious about Ramírez’s materials. He drew on whatever was at hand: A brown paper bag unfolded to make a scroll, supply forms, and hospital bed paper all served him. And it is heartbreaking to read that he joined these various bits of paper into larger sheets with a glue made from potato, bread, and saliva.

Ramírez’s ingenuity in concocting his glue extended to its use in fantastically whimsical collages. In one affecting variation on the Madonna theme, “Untitled (Rosenquist Scroll)” (1953), a black-and-white photographic image of a typical, smiling ’50s-era woman has been pasted into a sort of heaven-and-hell landscape. She wears a drawn hat and has antennae, or horns, protruding from her head. One gloved hand holds a rope, which both descends, tied to the waist of a boy in a receding tunnel, and ascends, coiling around what seems to be the trunk of a palm tree. Above is more of the semiabstract patterning — here tunnel or feather motifs — common to almost all the sheets.

A version of that heaven-andhell duality remains present through Ramírez’s oeuvre. Despite the desperate circumstances of their origins, these works always manage to express joy. He depicts his confining spaces as ornate decorations; he finds humor everywhere.

It was in the early 1950s that a professor of art and psychology, Tarmo Pasto, came upon Ramírez and his drawings, recognized their great inventiveness, and began introducing them to the public. Even when he could have left the hospital, Ramírez did not return to Mexico. We can be grateful to him and to Pasto that his work did escape to the world outside.

Until April 29 (45 W. 53rd St., between Fifth and Sixth avenues, 212-265-1040).