8 
in animals) is clamped to the transverse beam by means of a bar fixed 
by two screws and in this way may be firmly fixed. Where the 
arm of a large animal or man is being examined it may be necessary 
to nail the bone to the bar. 
The hand is clamped in the hole drilled in the lower of the 
two platforms. A disc which fits into the hole keeps the clamping 
bars rotating round a centre. 
The movements of the forearm that correspond to the movements 
of the hand are registered on a graduated circle, which is fixed to a 
platform not shown in the drawing and can be made to move up and 
down. 
The method of determining the degree of rotation at each part 
is simple : 
Suppose we wish to determine the movement a little above the 
wrist then the graduated upper platforme or circle is moved up or 
down to” theflevel of the place to be examined; a rule is passed across 
in front of and behind the limb. Those rules consist of thin steel rods 
which are secured at the ends and by means of a pointer the exact 
position of the plane is noted. 
The circle is shown larger than it really is. The circle requires 
to be just large enough to allow any limb to rotate freely. 
HEIBERG’s method may be also used viz. by inserting long pins 
into the bones and noting the amount of deflection. I have, however, 
been most interested in the determination of the rotation of the limbs 
and the share to which each part contributes. 
Having ascertained the amount of rotation at the wrist it is 
only necessary to move upwards the upper ring or platform in order 
to obtain the degree of rotation higher up. 
It is most important that the limb should be secured in such a 
way that its axis of rotation corresponds as nearly as possible to the 
centres of the platforms above and below. 
I have had the circle graduated in order to show the nature of 
the apparatus. 
The amount of rotation can be ascertained by the steel rules. 
The amount of flexion and extension in a single bone produced in the 
twisting can besascertained by means of a vertical sliding rule. 
A pin fixed into a bone where the flexion or extension is to be 
ascertained moves upwards or downwards according to the nature 
of the movement in the bone. As the degrees of flexion and extension 
are not considerable the scale rule is small. 
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