Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 3: Ins-Pla
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29464/478/
470 
MOTION. 
Fig. 260. 
vertical line, not only the time of swinging 
the leg has increased, but also the time in 
which both legs are resting on the earth ; for 
the latter commences at the instant when the 
forward leg has reached the ground, and termi¬ 
nates when the head of the femur has arrived 
at the vertical line, passing through the point 
of support of the same foot. The time aug¬ 
ments in proportion to the distance which the 
swinging leg passes beyond the vertical posi¬ 
tion, or half oscillation. The time when both 
legs are resting is greatest in fig. 260, because 
it must be sufficiently great for the head of 
the femur, together with the whole trunk, to 
advance to a position directly over the foot, 
during which the head of the femur moves 
very slowly, and by the direction of the for¬ 
ward leg its action is to retard the horizontal 
advance of the centre of gravity. The time is 
less in fig. 259, because the head of the femur 
has to pass through a less space, and the sup¬ 
porting leg acts against the trunk at a less 
angle; but in fig. 258 the time of both legs 
resting at the same time, disappears altogether. 
The two legs complete the least portion possi¬ 
ble of the vibrating curve, and the duration of 
each step amounts only to the time of half an 
oscillation. In walking very slowly we may 
suffer the swinging leg to vibrate so long, that 
it partly returns to its former position before.it 
reaches the ground. 
We have seen in quick walking that during 
the time both legs rest on the ground, the ad¬ 
vanced leg continually forms a smaller angle 
with the vertical than the hinder leg; but in 
very slow walking the forward leg may form a 
greater angle with the vertical than the hinder 
leg; the magnitude of this angle determines the 
kind of gait the walker acquires. In order to 
accomplish this, the swinging leg is suffered 
nearly to complete its curve of oscillation be¬ 
fore it is placed on the ground, and during this 
time the centre of gravity moves so little, that 
half the length of the step may not be at once 
described, and the entire duration of the step will 
be about four times greater than in the quickest 
pace.* In this case the forward leg really 
makes a greater angle than the hinder as it 
reaches the ground, but during the time that 
both legs are on the ground, the angle of the 
forward leg diminishes, whilst that of the 
hinder leg augments, and there is an instant 
when both legs form equal angles. When the 
angle of the forward leg becomes zero, or in other 
words, when it is directed vertically, the hinder 
leg rises from the earth ; for example, in fig. 
261, where a c represents the right leg, b c 
the left, in the beginning 
of a step, or the instant the 
foot a is raised from the 
ground ; c d" is the magni¬ 
tude of the step, or the 
space which the centre of 
gravity passes through in 
the time of a step, c" being 
the centre of that space. 
Now, if the foot a, which 
was raised at the begin¬ 
ning of the step, were placed again on the 
ground at a', at the instant when the centre of 
gravity reaches the middle point c", then both 
legs would form equal angles with the vertical ; 
or, the angle b c" a. — a c” a, in which 
c" a. is the vertical through c" ; but if the angle 
of the hinder leg to the vertical be less, when 
the right leg is set down in a', the centre of 
gravity will not have arrived at the middle 
point c", but at c'; however, whilst both legs are 
on the ground, the centre of gravity is pro¬ 
pelled from c to c", after which the angle b d cc 
increases and the angle o' c" a. diminishes 
(where d a. is the vertical through c); when 
the centre of gravity is propelled onwards from 
c" to d", the angle a c" a. is less than 6 c" a, 
until the termination of the step. 
In this slow method of walking a very mea¬ 
sured pace results, in which the body is carried 
very erect, and remains for a considerable time 
in the rear of the forward leg after it first reaches 
the earth ; consequently the duration of the 
step will be very considerable, nearly one se¬ 
cond and a half, the length of the step very 
short, and the velocity of the centre of gravity, 
which is very little at the middle of the step, 
varies considerably during each step, so that 
there is an instant in which the body is nearly 
at rest. This is denominated by Weber the 
grave or procession slepfi 
A remarkable difference may be observed in 
the duration of the steps of two different per¬ 
sons, one of whom has long and the other short 
legs. In quickest walking the duration of 
* That is, where T represents the entire duration 
of an oscillation of the leg, the time of a step in the 
quickest to that in the slowest walking will be as 
iTto2T, or four times that of quickest walking, 
t Vide Weber, loc. cit. sect. 139, p. 344.
        

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