But _leather_--indespensable for certain stumps which cannot stand a wooden bucket--has the advantage that it can be employed as a _temporary fitting_. During the first weeks, sometimes even for the first months, the shrinking of the stump can be accommodated by lacing up the bucket, and, when shrinkage is complete, the leg part of this first apparatus can be attached to a wooden bucket which the improved condition of the stump now renders possible. This form is a little more expensive (80 frs.) than "the poor man's leg," but I believe a great deal more comfortable. It may be added, that it is easy when the foot is fitted at the end of the apparatus to render flexion of the knee free and to attain the "American walk," of which we shall speak later. All that is necessary is to attach in front an artificial muscle of indiarubber, reaching from the thigh to the leg and an extending sling like that in the American limbs (see page 47). This appliance which we call the "Fédération Leg," because we designed it at the _Fédération des Mutilés_, has already been imitated without its origin being acknowledged. IV. WALKING WITH FREE FLEXION OF THE KNEE A. _Design._--The oldest type, which will suffice for studying the general conditions of stability, is that of Marks, with a fixed foot shaped out of the same piece of wood as the leg: the ankle joint--several types of which we shall describe later--does not affect the question of stability. The appliance is made entirely of wood; it is strong and light. Nothing need be added to the description already given of the fitting and method of attachment of the thigh piece, which ends below in a curved "condyle,"[4] which fits into the top of the leg piece. It is transfixed by a metal bolt, from each end of which a metal plate descends and is riveted into a corresponding groove in the leg.[5] This forms the axle which rotates in the thigh piece when the knee flexes or extends. Flexion of the knee is free. Extension is stopped just short of the straight line (see p. 16). [4] The bucket and the condylar portion are made of two separate pieces of wood. [5] The hole through which the bolt passes being cut in soft wood (willow or lime), must be strengthened by a cylinder of metal, of leather, or of harder wood (beech or service tree) in which the axle revolves. [Illustration: FIG. 48.--Marks leg with fixed foot.] [Illustration: FIG. 49.--Construction of the foot.] The foot is in equinus at an angle of 25° to 30° so that the heel is 2 or 3 centimetres from the ground (the usual height of the heel of a boot). The piece of wood which forms the instep and which is continuous with the leg stops at a point corresponding to the middle of the metatarsus, and is only half the thickness of the foot. The rest of the foot is shaped of indiarubber stuck on to the instep piece; the wood and rubber being enclosed in a sheath of leather.