Terrain au Cheval 1 is part of the three-part series Tables paysagées, Paysages du mental, Pierres philosophiques (1951-1952).  
These works, produced in Paris and New York, ‘aim to recreate the immaterial world that inhabits the human mind: a tumultuous disorder of images, of images being born, of images vanishing, overlapping and intermingling...’. 
For Dubuffet, landscapes are not more or less faithful reflections of an external reality but the transcription of mental images.

Our drawing, Terrain au Cheval 1, in Indian ink executed with a calamus, depicts a horse galloping across a plot of land. The animal, the only figurative element in the composition, creates a link between the concrete and the abstract, between the empty and the full. The very presence of the animal allows us to escape from pure abstraction. Its silhouette stands out against a blank sky, as empty as nothingness, in contrast to the rugged, tumultuous terrain. All Dubuffet's work bears witness to his attraction to the ground, subsoil, earth, texture and matter. Here, the surface of the ground is treated in a totally abstract way, using stains, scratches and drippings.
The artist commented: ‘For me, even the most accidentless and featureless pavement, any dusty bare earth, which no one would ever think of looking at, is a sheet of intoxication and jubilation [...]’. Jean Dubuffet.

The calame is a pointed reed that has existed since Antiquity.
Initially used for engraving in soft clay, it was only later used with ink, particularly in the Middle Ages, for manuscripts.