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In the present volume I have endeavoured to explain, in simple language, some difficult problems in “ Animal Mechanics.” In order to avoid elaborate descriptions, I have introduced a large number of original Drawings and Diagrams, copied for the most part from my Papers and Memoirs “On Flight,” and other forms of “ Animal Progression.” I have drawn from the same sources many of the facts to be found in the present work. My best thanks are due to Mr. W. Ballingall, of Edinburgh, for the highly artistic and effective manner in which he has engraved the several subjects. The figures, I am happy to state, have in no way deteriorated in his hands.


July 1873.


The body and wing reciprocate in flight; the body rising when

the wing is falling, and vice verså,
Flight the least fatiguing kind of motion. Aërial creatures not

stronger than terrestrial ones,

Fins, flippers, and wings form mobile helics or screws, .

Artificial fins, flippers, and wings adapted for navigating the

water and air, .

History of the figure-of-8 theory of walking, swimming, and

flying, . . . .

Priority of discovery on the part of the Author Admission to

that effect on the part of Professor Marey, .

Fundamental axioms. Of uniform motion. Motion uniformly

varied, . . . . . . .

The legs move by the force of gravity. Resistance of fluids.

Mechanical effects of fluids on animals immersed in them.

Centre of gravity, . . . .

The three orders of lever,

Passive organs of locomotion. Bones, .

Joints, . . .

Ligaments. Effects of atmospheric pressure on limbs. Active

organs of locomotion. Muscles ; their properties, arrange-

ment, modes of action, etc., . . . .
Muscular cycles. Centripetal and centrifugal movements of

muscles ; muscular waves. Muscles arranged in longitu-
dinal, transverse, and obligne spiral lines,


The bones of the extremities twisted and spiral,

Muscles take precedence of bones in animal movements,

Oblique spiral muscles necessary for spiral bones and joints,. 31

The spiral movements of the spine transferred to the extremi-

ties, . . . . . . .

The travelling surfaces of animals variously modified and

adapted to the media on or in which they move, . . 34-36

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