Part 36 (1/2)

Theprinciple: Suppose two rubber globes connected with one another by a tube If we colobes, the air which it contains will be driven into the other, and will afterwards return when the pressure has ceased Nothing more simple, evidently; but it is necessary to describe it in detail in order the better to comprehend that which follows: The walker who is the subject of experi thick indiarubber soles, hollowed in the interior, so that the whole thus constituted forms a sort of hollow cushi+on which is compressed under the influence of the pressure of the foot on the ground A tube which is attached to a registering apparatus, which the person who is walking carries in his hand, co 116)

This apparatus is formed of a metal drum, which is closed at its upper part by a flexible meround, the air contained in the cavity of the sole of the shoe is driven into the drum, which we have just mentioned, and the flexible membrane of this drum is elevated To this membrane is attached a vertical rod which supports a horizontal style

[Illustration: FIG 115--EXPERIMENTAL SHOES, INTENDED TO RECORD THE PRESSURE OF THE FOOT ON THE GROUND]

When the membrane, as we have just seen, is elevated, the style is lifted, and then descends when the pressure of the foot ceases It traces these displacements on a leaf of paper, the surface of which is covered with a thin layer of lamp-black, which it removes by its contact; different parts of this surface are successively presented to it, the paper being rolled round a cylinder which is turned on its axis by means of a clockwork movement It is necessary to add that the inscription is made, in the study of the walk ofto one of the feet

The tracings thus obtained, which are read froht, are sufficiently simple; but to understand theoes aeach pressure of a foot, and that, on the other hand, it descends when the latter is separated fro which it leaves, a line which ascends and then descends; the round, and is afterwards raised from it

[Illustration: FIG 116--RUNNER FURNISHED WITH THE EXPLORATORY AND REGISTERING APPARATUS OF THE VARIOUS PACES]

On the tracing (Fig 117), the line D relates to the right foot; the line G, which is dotted so that it , corresponds to the left foot The line G first ascends; the round; afterwards it descends: this indicates that the pressure of the foot has ceased It is the saht foot As we see, the pressures succeed each other; when the left foot touches the ground, the right is separated froround, it is the left which no longer rests there

The line O is related to the movements of the body, as indicated by the oscillations of the head We will neglect these

But this tracing, which serves us for an exa; it would be still less so if the paces of a horse were registered, for there would then be four lines, the entanglereater co need be no longer feared, if we transforra two horizontal lines (1, 2) From the point where the line D rises (coht foot), and from the point where this same line descends (end of the sa the two horizontal ones mentioned above At this plane, and between the two vertical lines, we th, the duration of the period of pressure of the right foot In doing the same for the line G, we obtain for the indication of a pressure of the left foot an interval of the saray, in order to avoid all confusion with the preceding tracing

[Illustration: FIG 117--TRACING OF THE RUNNING OF A MAN (AFTER PROFESSOR MAREY)

D, Pressures and elevations of the right foot; G, pressures and elevations of the left foot]

This notation can, with sufficient exactitude, be compared to that which is employed in the musical scale The horizontal lines 1 and 2 represent the _compass_ We there also see _notes_; these are the bars indicating the pressure, of which the value--that is to say, the duration--is represented by the length of these bars It is the saard to the intervals of _silence_: these are expressed by the intervals which separate the pressures, and correspond to the , the body is raised froround

Besides, we see intervals of this kind on the notation reproduced (Fig

118) relative to the running of man

[Illustration: FIG 118]

[Illustration: FIG 119]

In order to s still better understood, we reproduce four varieties of the 119)

The first notation is that of ordinary walking The pressures succeed each other regularly

The second shohat takes place during the ascent of a staircase At a certain ht of the body is upon both feet at the sa the lower step, until the other is already in contact with the step above Accordingly, there is thus produced an overriding of the pressures

The third is relative to running, and has already been represented in Fig 118 The pressures of the feet are separated by the ti, but in this case more rapid and characterized by the shorter pressures, the slightly longer periods of suspension intervals, and the quicker succession ofto the walking ive in order to render intelligible those which are connected with the paces of the horse--we have yet to fix the value of that which we call 'a step'

It is generally admitted that a step is constituted by the series ofphases of the action of one foot and that of the other--for exaht foot coround and that at which the left foot commences its own It is necessary to adopt here anotherbut a _half-step_ The step should then be defined as being constituted by the series of movements which are executed between two similar positions of the same foot--as, for exaht foot and the si pressure of the same foot We shall soon understand the i on the details of the paces of the horse, it is necessary to see how the li the period of a co, to determine what the displacements are which a limb executes between two similar positions of its foot

If we exa a forward h two principal phases: (1) It is raised froround Each of these phases is divided into three periods of time, which we proceed to analyze in connection with the anterior limb

[Illustration: FIG 120--SWING OF THE RAISED ANTERIOR LIMB (AFTER G