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1407 E. Michigan Ave., Jackson 517-784-1142 770 Riverside Ave., Suite 101, Adrian 517-263-3310
CHAPTER II - Artificial Feet, Their Construction And Relative Merits
THE RUBBER FOOT. - With an experience of eight years in manufacturing artificial legs with wood feet, articulating at the toes and ankles, A. A. Marks in 1861 invented the sponge rubber foot hereinafter described, to protect which the United States Government issued letters patent in 1863. Like all great inventions it passed through various stages of development.

The perfected form consists of a wooden core, carved to size and shape to secure the best results. The faint lines in Cut B 1 represent the core, which reaches to the ball of the foot, localizing the toe movement. The distance from the core to the floor at the heel is considerably greater than at any other part; this is done to obtain the proper degree of compressibility at the heel; the core is entirely surrounded with sponge rubber of great porosity which will yield under the weight of the wearer sufficiently to make the step realistic. Less rubber is placed at the ball so as to provide phalangeal support and make the wearer feel that there is a supporting medium at the front of the foot; ample, to steady him when standing, to keep him from limping, and to act as a lever to urge him forward when walking. A spring mattress is floated in the foot below the core, covering the entire distance from the back of the heel to the tips of the toes; it is shown by the lines running lengthwise in Cut B 1. The spring mattress is formed by a series of composition strips embedded in strong sail duck, each having a pocket of its own, see Cut B 2; the strips occupy the pockets a a a a.

THE SPRING MATTRESS. - Is a device for giving additional resiliency for both the toes and heel. Every movement of the foot when in action applies pressure to the springs at the heel, ball, or on the sides. The counteracting tendency of the strips aids in forcing the foot back to its proper shape as soon as pressure is removed.

Cut B 3 represents the rubber foot with the weight applied at the ball as it is when the wearer is being urged forward, while walking. The spring mattress is now forced upwards at the ball and the sponge rubber is compressed above and below the mattress. This pressure pulls the mattress forward in the foot. These movements - the yielding of the spring, the compressing of the rubber, and the pulling of the spring mattress forward - form a very powerful resultant force that brings the foot back to its normal lines as soon as the foot is relieved of weight.

The condition of the foot when under heel pressure, as it is when the wearer places the artificial limb forward and applies his weight upon it, is somewhat the same. The spring mattress is forced upward, the sponge rubber is compressed above and below, the heel becomes flattened, and the mattress being pulled lengthwise, all combine to force the foot to its shape as soon as pressure on the heel is removed. The compression of the heel permits the toes and the front part of the foot to reach the ground while the shaft of the leg is obliquely back of the vertical line.

Cut B 4 represents the foot on an inclined surface. On account of the yielding quality of the rubber, the up-hill side of the foot will compress and accommodate itself to the incline and allow the foot to remain on its base. This is accomplished without complicated mechanical lateral articulation.

The spring mattress not only forces the parts of the foot back to their proper shape, but obviates the exertion required to operate the antiquated articulated wooden foot.

The impression that one receives on the new spring-mattress foot is both pleasant and agreeable. This is especially the case to one who has worn an artificial leg with wooden articulating foot.

It can readily be seen that any motion in the ankle that cannot be controlled by the will must be mechanical in appearances as well as in action. The approach to nature is made more positive by their omission.

It is the experienced man, the man who has experimented with many kinds of artificial limbs, who is capable of appreciating the principles involved in the rubber foot. He comprehends the reason why the wearers of artificial limbs with rubber feet walk further, faster, and with less fatigue, than those walking on ankle-jointed wooden feet.

The contrast between the two kinds is most striking in running. With the rubber as with the natural foot the entire plantar surface is never on the ground. It is the heel-and-toe touch to the ground that distinguishes the walker from the runner. This is extremely difficult with the ankle-jointed foot. When standing the immovably attached rubber foot furnishes a large base on which to balance; hence, a man with two artificial legs with immovably attached feet can stand restfully and safely without assuming awkward and unnatural positions, for he is not required to maintain his equilibrium on a point.

The rubber foot with spring mattress provides the laborer a substantial substitute with which to support and brace himself when working at the bench, on the road, on the farm, or at whatever occupation he may be engaged. There are no uncertain or treacherous movements to hamper him or make his position uncertain.

A painter who wears a Marks rubber foot says he can climb a ladder, stand on a scaffold, balance himself at any elevation with absolute safety. With an ankle-joint leg he would feel tottlish, and, when on his ladder, would have to depend more on the grasp of his hands than on his foot; but, with the rubber foot, his base is substantial and reliable.

A farmer who toils in the field can plod along over stony or muddy ground on a rubber foot with safety. The accumulation of mud on his shoes does not cause his toe to drop and trip him. Uneven surfaces will not throw him from his balance or violently jar his stump. We have thousands of testimonials on these points.

CONTRASTS. - There are two kinds of rubber feet. One is known as the sponge rubber foot; and the other as the pneumatic rubber foot. We will endeavor to make clear the difference between them.

When rubber is cured so that it possesses a great number of small air cells, the same as a sponge, it is called sponge rubber, and a foot made in this way is known as a sponge rubber foot.

A foot made of a sheet of rubber cast into the shape of a foot, possessing one or a limited number of large chambers into which air is pumped until sufficient pressure is obtained to maintain shape and possess resiliency is called a pneumatic foot.

THE SPONGE RUBBER FOOT. - Is composed of a vast number of cells, each charged with air created by the volatilization of a chemical while the rubber is being vulcanized. Each cell is surrounded by a wall of rubber possessing a sustaining power sufficient to maintain itself should it become deflated. In fact, if all the cells become deflated the foot would keep its shape on account of the presence of the sustaining walls, therefore the shape and resilience of the sponge rubber foot are not dependent upon the air in the cells.

THE PNEUMATIC FOOT. - Having but a limited number of large air chambers into which compressed air is forced, is wholly dependent upon the presence and retention of the compressed air for its stability. The sponge rubber spring-mattress foot receives no injury from puncture. The pneumatic foot will collapse and lose its sustaining power the moment the air chamber is penetrated. A protruding nail or peg in a shoe will puncture a pneumatic foot and put it out of service until the puncture is patched and the foot pumped up again with air.

The sponge rubber spring-mattress foot never has to be recharged with air.

THE WOOD FOOT. - Is now somewhat antiquated. It no longer has the merit it was formerly thought to possess - the rubber foot has practically supplanted it: The wood foot is articulated at the ankle and at the toes. The mechanical methods employed in its manufacture are as numerous as the makers who supply them. Nearly every maker has a method of his own, yet all are essentially the same. Some admit of a large range of ankle articulation, while others limit it so that there is but very slight motion. Some have side motion; others, equally as conscientious, condemn that motion and employ only front and back motion. Being convinced by most careful study and experimentation that an artificial leg is improved in proportion to the abridgment of its mechanical movements, we dissuade all from using the side motion. Some manufacturers employ rubber for springs in the ankle and toes; others prefer steel. One method has little advantage over the other.

THE ANKLE-JOINT RUBBER FOOT. - Cut B 5 represents an ankle-jointed rubber foot after our preferred plan. Cut B 6 represents the ankle articulation in sectional view. The axis on which the foot moves consists of a bolt that passes through the foot at the ankle, connected with steel strips riveted to the lower sides of the leg. A steel spiral compression spring, one end of which is placed in a cylinder and the other, receiving a piston, is placed in the ankle in such manner as to act on the rear part of the foot, impinging against the front interior part of the socket, forcing the heel downward and the front of the foot upward. The articulation at the ankle is limited by the check cord placed in the rear. It is made of the strongest flexible material. This method of articulation can be used with wooden feet as well as rubber ones. When rubber is used it is not necessary to have a mechanical articulation at the base of the toes as the rubber itself will furnish that motion. Cut B 7 represents the ankle at extension, the foot flat on the ground when the leg is thrown forward and weight applied. Cut B 8 represents the ankle at flexion and weight applied to the toes.

THE FELT FOOT. - Is so seldom used that it is only referred to here in order to make our descriptions complete. Its use is to be strongly condemned. Felt possesses no stability. It is an absorbent of moisture and lacks resiliency, and is therefore wanting in the most essential qualities that should characterize the material used in the construction of an artificial foot.

ANKLE JOINTS WHEN ORDERED. - While many years of observation and study have convinced us that the best results are obtained from artificial legs with rubber feet rigidly attached, it is nevertheless true that some persons form prejudices that cannot be removed even by the most logical arguments. Another class, who may be put in the same group, are those who, for a long period, have worn artificial limbs with articulating ankles; and have become so inured to them that a change, no matter how beneficial it might ultimately prove, would subject them to annoyance. We care not to antagonize those who think and feel this way; we are therefore prepared to construct artificial legs for them that are similar in construction to those they have worn and have become accustomed to.

We frequently hear of persons who are inclined to patronize us on account of the reputability of the house, but who hesitate in doing so on account of their doubts as to whether they themselves would make a success with artificial legs without ankle articulations. The idea of the rubber foot is acceptable, but rigidity at the ankle is doubtful. The element of doubt hinders their entering into any experiment the success of which is entirely at their risk.

We are disposed to meet any such person on a basis of equity and will furnish him with an artificial leg with rubber foot rigidly attached at the ankle with the understanding that, if after reasonable trial he feels that he would prefer the ankle joint, we will apply one for him without extra charge.

As we regard rubber feet rigidly attached at the ankle better for general purposes, we make limbs that way unless otherwise instructed.

Prices are the same whether rubber feet are permanently attached or made to articulate, whether feet are of wood, metal, or rubber.

Comment from follow-up survey
Very friendly and kind, seems to truly care about the comfort of my brace.