“La Main de Picasso,” at Galerie Gmurzynska New York, features just one object: a plaster sculpture of Pablo Picasso’s left hand, the only known surviving cast to exist. The gallery is narrow, and the hand is at its far end, behind velvet ropes. It is a greeting, a signal to halt, a gesture of benediction, and a relic reminiscent of the dismembered saints of old. Visit it until November 10 to reflect on the hands that made art modern. 

Picasso was right-handed, making his left the only one that could serve as his subject. He sculpted his lesser hand the same year, and in the same studio, that he composed “Guernica,” his tableau of escalating horror that features a riot of club-like hands outstretched in balletic agony and futile prayer. The painting concerns the bombing of a town in Basque country by Benito Mussolini and Adolf Hitler. It is a masterpiece, and has become a meme.

Picasso began sculpting in his early 20s, and never stopped throughout his long life. Between 1930 and the middle of the 1940s, the master worked largely in plaster. A learned catalog written by a veteran curator, Jérôme Neutres, notes that Picasso “deemed the bronze casts of his works as too impersonal,” and preferred the inchoate, fetal form of plaster. The hand looks like mummified flesh. Its counterpart is in the Musée Picasso in Paris.

The hand is also mysterious, as Mr. Neutres notes of its provenance only that it is “owned by a prominent collector who acquired it from the Picasso Estate” and that this “mythical work has not been exhibited in public for more than twenty years.” Picasso’s left hand was something like a celebrity in his lifetime; the poet Max Jacob used it as a model for his “Study of Chiromancy.” Jacob saw in Picasso’s palm the evidence of a “vast and deep soul.”

Other contemporaries were struck by Picasso’s fixation on creating avatars of his own digits. A Franco-Hungarian photographer, Brassaï, reports in his “Conversations with Picasso” that his interlocutor “dips his hands in fresh plaster and makes casts of them” in order to measure their “concentrated power.” For Brassaï, Picasso’s hands in both art and life were symbols of his creative power.” The hand appeared to “model itself.”

Picasso’s “creative power” verged on the superhuman. His artistic life was so fecund that it is divided into periods, like an ancient empire or the earth’s eras: Blue, Rose, Analytic Cubism, Crystal, and others besides. Paintings like “Les Demoiselles d’Avignon” and “Guernica” define the 20th century just as Vincent Van Gogh’s and Leonardo da Vinci’s creations did for earlier epochs. His art is the bedrock upon which innovations still to come will be built.  

That is why it is strangely moving to encounter this paw print of a lion of the avant-garde. The lines of his palm are deeply grooved, the hand fleshy and dense. The fingers are not long, but are plainly accustomed to labor — if not weather-beaten, then art-beaten. Detached and aloft, it is both artwork and an anatomical autobiography of the artist. You look at it, and then down at your own hand, and wonder over the differences.