Abstract: A matress has a layer of a material formed of or including vegetable fibers which may be covered on one or both faces with a layer of foam material which is capable of undergoing a localized deformation along a fold line while retaining the continuity of its surface. The layer of material including vegetable fibers is constituted by at least two blocks having a junction zone which is located roughly in a transverse plane and along a fold line. A layer of foam material is provided in the vicinity of the junction zone on each side of a transverse plane, this layer of foam material being fixed to each of the upper and lower faces of the layer of material including vegetable fibers.