On the Movement of Animals, Part One

will proceed by an oblique motion to a position perpendicular to the horizon. And the same will happen if the fibers AB, CD were consistent and flexible, like the small branches of trees; but in this case the rhomboid will retain a greater amplitude. Let us now see if, by shortening the ropes AB, CD, or by pulling them upwards, or by wetting them, there follows an elevation of the ropes together with the weight R attached. And we observe, d Tab. 1. Fig. 5. d that in order that the adhesion and union of the rods BD and AC, and the inclination of the whole rhomboid, be prevented, it is necessary that the rod BD be held back by transverse bonds, or by powers X, Z pulling transversely; and then, with the ropes contracted, BD will approach towards AC by a motion equidistant to themselves; nor will the ropes ever be lifted around the center A towards AG, so long as the rod BD is pulled downwards by the weight R. Wherefore, by means of a simple rhomboidal muscle, the motive force of the fibers will not be able to lift the resistance R.

e Tab. 1. Fig. 8.

It is true, however, that in some case the proposition can be verified, e as if the fibers were fastened to a firm bone EAC, and the side of the rhomboid BD were held in a smoothed and lubricated channel LF excavated in a column, then indeed, by the contraction of the fibers AB, GH, CD, the tendon BD with the attached weight R could indeed be pulled obliquely upwards. But this hypothesis has no place in animals, in which such simple muscles having a rhomboidal form are not found, whose tendon, or mobile side BD, runs within a smoothed channel: wherefore it must be concluded that such simple muscles are neither found in nature, nor do they act in the way those illustrious authors think. But such action can take place only in some muscles composed of several rhomboids, as in its proper place