IMPROVEMENTS IN THE CONSTRUCTION OF ARTIFICIAL LEGS
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Henry Heather Bigg at the
Office of the Commissioners of Patents, with his Petition, on the
30th December 1868.
I, HENRY HEATHER BIGG, of Wimpole Street, Cavendish Square,
in the County of Middlesex, Anatomical Mechanician, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN THE
CONSTRUCTION OF ARTIFICIAL LEGS," to be as follows:-
The distinguishing features of this Invention are,-
1st. The construction of the ankle joint and the mode of connecting
the foot to the lower part of the leg. My improved mode of constructing
the ankle joint admits both of antero posterior and lateral or horizontal
inotion.
2nd. The means of constructing, attaching, and moving the knee
joint.
The ankle joint consists of two distinct parts made of wood, vulcanite,
bone, or any other suitable material. The lower part, which forms the
foot, has a cup-like hollow or socket with two notches provided with
blocks of india-rubber one ou either side. A hole or aperture is made
through the centre of the cup for the passage of an elastic cord or

page_text: tendon. The other or upper portion or ankle part consists of a block
of wood or other material with a hollow cup or socket made therein, into
which is fitted a spherical block or ball of any suitable hard material.
This spherical block or ball has a hole made through its centre for the
passage of a strong cord of catgut, chain, twisted thread, or other tough
material which acts as a tendon. The spherical block or ball is provided
with two lateral half round pins, which form the ankle joint by fitting
into corresponding notches at the lower part of the leg. The flat part
of these pins rests on the india-rubber blocks at the side of the cup or
socket of the foot. The pins rock horizontally on these blocks and thus
form a pivot or pin joint, thus permitting of antero posterior and lateral
movement combined. Just behind the cup is a circular or oval aperture
for the passage of a catgut cord, which is surrounded by a spiral or
helical spring formed of metal wire, and which when jointed to the foot
gives an uplifting motion to the whole of the foot and presses the heel
downwards. The two parts of the foot are joined together by two cords
or tendons, one passing through the centre of the spherical block or ball
and having at its upper part an india-rubber collar and vulcanite screw
fixed to the woodwork of the leg to give both tension and elasticity to
the joint and keep it close to its work, and which also fastens to the
under surface of the foot by a horizontal peg or staple. The other cord is
firmly fixed to the under surface of the heel and is secured to the wood-
work forming the calf of the leg. Around this heel cord is placed a
helical wire spring for giving motion to the ankle joint. The base of
the foot is covered with india-rubber to deaden sound and impart
elasticity to the tread.
The knee joint consists of two blocks of wood joined together by a
metal rod or bolt, and motion is given to it by a catgut, wire, or other
tough cord passing over it and secured at the lower end by an india-
rubber cord to the leg part, the upper part of the cord being firmly fixed
to the woodwork of the thigh. The effect of this cord is to throw the
leg forward or straighten it when flexed. The whole leg is covered with
a delicate skin and enamel similar in color to the human flesh, and it
can be washed when needed.