MOTION. 
411 
Fig. 214. 
ing them. There are no examples of the 
ound pulley in animal structures. 
€ recognise the simple pulley in the trans- 
sion of the tendons of the peronei muscles 
gh the groove of the external malleolus of 
man ankle-joint, in the tendon of the obtu- 
‘internus gliding through the groove in the 
chii, in the tendon of the circumflexus 
i passing through the hamular process of 
phenoid bone, in the tendon of the obliquus 
erior gliding through the ring attached to 
frontal bone, and in several other instances 
2 a change of the directions of the limbs 
alts from tendons passing over joints, through 
Oves in bones, or under ligaments, by which 
-muscles are capable of producing effects 
‘distant organs without disturbing the sym- 
try of the body, an effect which, owing to 
mited power of contraction in the muscles, 
be accomplished in no other way. 
uniform motion.—If a body move 
stantly in the same manner, or if it pass 
ual spaces in equal periods of time, its 
is uniform. The velocity of a body 
uniformly is measured by the space 
h which it passes in a given time.* 
velocities generated or impressed on 
nt masses by the same force are reci- 
y as the masses.+ 
uniformly varied.—When the mo- 
of a body is uniformly accelerated, the 
it passes through during any time what- 
oy eh io the square of the time. 
e leaping, jumping, or springing, of 
in any direction, (except the vertical,) 
yaths they describe in their transit from one 
nt to another in the plane of motion are pa- 
lic curves. 
ie legs move by the force of gravity as a 
‘Thus if v be the space passed over by the bod 
1 unit of time, that space x by ¢, or ¢v will 
€ Space s passes over in ¢ units, that is, 
STV. ew eee te wee . 
If a force communicates a velocity » to a 
m, and a velocity v’ to a mass m’, then we 
te Ueno ©) ss 
lly, if f be the accelerating force, the space 
$= 
tv 
= eovveccecessesec(4), 
. - 
4LOttLO 
2, Peeesseeeesr re ). 
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. 
Half 
Length| dura- 
of leg. | tion of 
No. in me- |oscilla- 
tres.* | tion. 
m “i 
1 | 0.831 | 0.370 |An exarticulated freely suspended leg. 
2 | 0.866 | 0.371 |The same. 
A leg suspended to the trunk by the 
3 | 0.831 | 0.355 } ligaments only, the muscles of the 
hip joint having been cut through. 
4 | 0.831 | 0.355 i Jes. of the dead body in its natural 
A living leg swinging uninfluenced 
5 | 0.860 | 0.346 { by the action of muscles. 
6 | 0.860 | 0.322 jA living leg walking on the het ; 
7 | 0.860 | 0.393 1S Beitr ck leg walking on the ball o: 
* A metre = 3.2808992 feet. 
A millimetre = 0,03937 inch. 
