You're using an outdated browser and can not see this website's design. We've allowed you to access all the content however, so you're not missing anything other than the pretty wrapper. Please download any browser that supports standards to view the full site.
1407 E. Michigan Ave., Jackson 517-784-1142 770 Riverside Ave., Suite 101, Adrian 517-263-3310
CHAPTER XIX - Wooden Hands. Rubber Hands
OLD METHODS. - During the first decade of our prothetical career (from 1853 to 1863), we manufactured mechanical hands, they were carved from wood with fingers jointed at the knuckles, controlled by straps operated by the shoulder. By a forward motion of the opposite arm, the strap would apply a pulling force to the artificial hand and force it open. By relaxing, the strain on the strap would be released and the hand would close. It would seem as though a hand of this character would be useful and valuable, but when the invariableness of the spring tension, the oppressive harness to be worn, and the exertion required to operate the straps were considered, it was doubtful that the results obtained justified the means employed.

NEW METHODS. - In 1863 our attention was attracted to the utilization of rubber, the resilient nature of which appealed to us as being better adapted to the purposes of an artificial hand than harsh, unyielding wood or metal. The rubber hand was thereupon invented. It was cast in a mold made from the model of a natural hand, and it was attached to the end of the artificial forearm by means of a spindle. The fingers were flexible and would yield under pressure, having sufficient elasticity and adhesion to hold light articles. It presented a natural appearance and was pleasant to the touch. It was far more durable than the wooden hand. It might fall or strike a hard object and would not break. It could be slipped from the socket and a hook, knife, fork, brush, ring or other implement put in its place. For a number of years this hand found many purchasers, and was greatly admired. Improvements were suggested from time to time.

DUCTILE FINGERS. - A fortunate thought was that of changing the fingers from flexibility to ductility. Flexible fingers would move under pressure, but as soon as that pressure was released they would return to the positions in which they were cast. The ductile fingers admit of change of position. The wearer can, by the opposite hand, or by pressing the fingers against some resistant object, change their positions from full extension to clinched. The hand with fingers partly closed is sufficiently firm to carry a valise or package. Cut O 1 represents the rubber hand partly closed. The dotted lines indicate the positions of extension and flexion in which the fingers can be bent.

PALM LOCKS. - A lock embedded in the palm, shown in Cut O 2, receives and hold implements with firmness. A hand brush, a knife and fork (as shown in Cut O 3) can be thus placed and have the appearance of being grasped by the fingers. When it is required to carry articles of considerable weight for a great length of time a steel hook is slipped in the palm socket, and, concealed by the hand, it is held with sufficient strength to carry an article of one hundred pounds in weight. A knife or fork can be put in the same socket; the latter will hold a piece of meat while it is being cut with the opposite hand, and will convey food to the mouth. A brush placed in the palm lock can be used in washing the opposite hand. When it is desired to remove an implement a little pressure is applied to the button and the implement is released, and can easily be taken from the socket.

WRIST CONNECTIONS. - Rubber hands are attached to forearms by various methods.

Cut O 3 represents the spindle method. A steel spindle is attached to the base of the hand, and made to fit a locking plate secured to the base of the forearm socket. The hand when so placed will rotate at the wrist if the wearer wishes. When it is desired to remove the hand a little pressure applied to the button will release the hold, it can then be taken from its place. When it is desired to prevent the hand from rotating a set screw is turned inwardly, and the hand is clamped firmly in one position. A variety of implements are illustrated in the cuts O 4 to O 7, each can be placed in the forearm substituting the hand.

CLAMPS. - Cut O 8 represents a new device for a wrist-joint connection, it is intended for a person who works at the bench. The end of the forearm is made of aluminum, and provided with a sliding jaw operating as a vise. A cold chisel can be held firmly at any convenient angle, shown in Cut O 9; a saw-file can be used to advantage, as shown in Cut O 10. A jeweler’s hammer, or in fact any implement with a handle not greater than 5/8 of an inch in diameter can thus be held in a thoroughly practical way.

FLEXION. - The mortise and tenon wrist connection is preferable to any wrist mechanism that admits of flexion and extension. Cut O 11 represents this method. The mechanism consists of a series of interlaying strips, held together by a bolt, which forms the axis of motion. Rotation of the arm is obtained, when desired, by means of a bolt connection introduced immediately above the wrist joint.

Cut O 12 represents the mortise and tenon connection, the hand flexed holding hook. Cut O 13 shows the hand extended, with fork held by the palm lock, the knife and other implements are held in the same way.

For laborers who wish to obtain the greatest variety of practical uses from artificial arms, the spindle connection at the wrist (Cut O 3) is preferable. This device admits of greater strength and enables the wearer to press the artificial hand against any object desired to be held in place. The mortise and tenon wrist connection, illustrated in Cut O 11, is chosen by persons seeking ornament more than utility.

When lightness is a paramount consideration it is advisable to have the hand permanently attached at the wrist.

This method obviates any metal connection, and thereby lessens the weight.

SPRING THUMB. - We have a mechanical device by which the thumb can be made to move at its base, away from or toward the fingers.

Cuts O 14 and O 15 represent the hand with the thumb abducted; this is effected by tension applied to a cord passing from the under side of the base of the hand upwardly to the elbow. Cut O 16 represents the hand with thumb pressed against the finger. As soon as the tension of the abductor cord is released, the thumb will be forced by a strong spring to press against the index and middle fingers. When the abductor cord is connected with the artificial arm above the elbow, the thumb will press against the forefinger when the elbow is flexed, and will draw away from it when the elbow is extended, as shown in Cut O 16. The abductor cord may be carried up the arm, over the back, around the opposite shoulder, by which it will be controlled. When thus connected it is independent of elbow motion and is operated by a movement of the shoulder or contraction of the chest.

As considerable mechanism is required in the spring thumb, the construction is more or less complicated, and we do not advise its selection except in special cases. In double amputations, when all dependence must be placed upon artificial means, spring thumbs are advantageous; but in single amputations they prove to be quite useless; the remaining natural hand becomes so adept that it performs about all the work that prior to the amputation was performed by both hands.

GLOVES ALWAYS TO BE WORN. - Artificial hands and parts of hands must be gloved at all times. This is necessary in order to conceal the fact that they are not real. Artificial hands, whether made of wood, rubber, or other material, may be molded to the shape of nature, and have all the graceful lines, creases, and fold that are found in the natural hand.

They may be painted and tinted with artistic nicety, yet it is not possible to impart to them the characteristics which distinguish nature from art. The natural hand has a different tint in the forenoon than it has in the afternoon; when the fingers are extended there are more creases in the skin than when they are flexed; when the hand is at labor it is broader and the muscles and blood vessels show with more prominence than when at repose. An artificial hand, no matter of what material it may be constructed, cannot possess this metamorphic power. It, therefore, must be concealed by a glove, otherwise it will be conspicuous.

CHOICE OF MATERIAL FOR SOCKETS. - Sockets for artificial arms may be made of wood, leather, or aluminum, to suit the wishes of the purchaser. Makers of experience are united on this point, and advocate the use of tough, light wood. Wood is capable of being worked into convenient shapes, which it will retain indefinitely. It is lighter than any other material that can be used, and when strengthened with rawhide is sufficiently strong for most purposes. It is also a non-conductor of heat, and when varnished does not absorb perspiration. The objection to leather is its flexibleness. While this may appear to be desirable, it is actually the cause of trouble. A socket that is flexible cannot be comfortable to wear, as it does not place the pressure at points of toleration; instead, it distributes it uniformly over the entire surface, causing pressure to come as much on sensitive parts as elsewhere. Leather absorbs perspiration, becomes foul and offensive, and unless extraordinary methods are used to keep it clean it will become hard and dead, it will crack and fall to pieces.

Leather sockets are sometimes unavoidable; they will be spoken of in due course.

Metal sockets are objectionable on account of their weight, liability to corrode from perspiration, and their disposition to hold heat. When arms are to be made for persons who work in water, such as dyers, laundrymen, fishermen, oystermen, etc., it will be necessary to use metal, such as aluminum, which receives no injury from exposure to moisture free from salt.

A rubber hand permanently attached to an aluminum socket will provide a useful, resistant, and durable arm, and when frequently cleaned and coated on the inside with sweat-proof enamel or paint will last a great many years.

Comment from follow-up survey
The office staff is great. My daughter walks in and Alice reads her books. Thank you for your great help in making her legs straight.