Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 3: Ins-Pla
Todd, Robert Bentley
Fig. 214. 
moving them. There are no examples of the 
compound pulley in animal structures. 
We recognise the simple pulley in the trans¬ 
mission of the tendons of the peronei muscles 
through the groove of the external malleolus of 
the human ankle-joint, in the tendon of the obtu¬ 
rator internus gliding through the groove in the 
os ischii, in the tendon of the circumflexus 
palati passing through the hamular process of 
the sphenoid bone, in the tendon of the obliquus 
superior gliding through the ring attached to 
the frontal bone, and in several other instances 
where a change of the directions of the limbs 
results from tendons passing over joints, through 
grooves in bones, or under ligaments, by which 
the muscles are capable of producing effects 
on distant organs without disturbing the sym¬ 
metry of the body, an effect which, owing to 
the limited power of contraction in the muscles, 
could be accomplished in no other way. 
Of uniform motion.— If a body move 
constantly in the same manner, or if it pass 
over equal spaces in equal periods of time, its 
motion is uniform. The velocity of a body 
moving uniformly is measured by the space 
through which it passes in a given time.* 
The velocities generated or impressed on 
different masses by the same force are reci¬ 
procally as the masses .f 
Motion uniformly varied.—When the mo¬ 
tion of a body is uniformly accelerated, the 
space it passes through during any time what¬ 
ever is proportional to the square of the time. 
In the leaping, jumping, or springing, of 
animals in any direction, (except the vertical,) 
the paths they describe in their transit from one 
point to another in the plane of motion are pa¬ 
rabolic curves. 
The legs move by the force of gravity as a 
* Thus if « be the space passed over by the body 
in an unit of time, that space X by t, or t v -will 
be the space s passes over in t units, that is, 
s = t ............(1). 
t If a force communicates a velocity v to a 
mass m, and a velocity v to a mass m, then we 
have mv = m v'..............(2). 
Generally, if /be the accelerating force, the space 
s=2 fiz>..............(3). 
tv. ... 
pendulum. — To the many instances already 
recognised of the connexions subsisting be¬ 
tween the functions of living animals and the 
physical sciences, another remarkable con¬ 
tribution has been recently added by the Pro¬ 
fessors Weber, whose experimental researches 
satisfactorily demonstrate that the swinging 
forwards of the legs of animals in progres¬ 
sive motion obeys the same laws as those 
of the periodic oscillations of the pendu¬ 
lum. In order to ascertain these relations, 
MM. Weber instituted a series of experi¬ 
ments upon legs of given lengths, both 
in the living and dead subject, and under 
variously modified circumstances. Having 
removed a leg from the trunk at the hip- 
joint, and suspended it by a short thread 
that it might move as if upon the axis of the 
head of the femur; upon giving it an im¬ 
pulse they found it oscillated nearly in the 
same time as in the living state. They next 
communicated a vibratory motion to a leg sus¬ 
pended to the acetabulum by the ligaments of 
the hip-joint only, the muscles having been 
previously cut through : in this experiment the 
oscillatory movements were rather less than in 
the preceding. The oscillations of the leg 
of a dead person after the rigidity of the muscles 
had subsided, were still further diminished. 
On comparing the durations of the vibrations 
of the legs in these several states with those of 
the living, they found their periods nearly equal 
or in the following proportions. 
of leg. 
tion of 
in me¬ 
An exarticulated freely suspended leg. 
The same. 
r A leg suspended to the trunk by the 
! ligaments only, the muscles of the 
t hip joint having been cut through. 
/ A leg of the dead body in its natural 
l state. 
/ A living leg swinging uninfluenced 
1 by the action of muscles. 
A living leg walking on the heel, 
f A living leg walking on the ball of 
\ the foot. 
* A metre = 3.2808992 feet. 
A millimetre = 0.03937 inch. 


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