A handbook to the cases illustrating animal locomotion / Horniman Museum and Library.

  • Horniman Museum
Date:
1912
Catalogue details

Licence: In copyright

Credit: A handbook to the cases illustrating animal locomotion / Horniman Museum and Library. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    tree.” Gould has also described this terminal ascent in a parachuting marsupial (Petauris australis) as preventing the shock the animal would otherwise sustain. It will be observed that the name “ flying ” popularly applied to so many of the parachuting animals is a misnomer, as, of course, they do not really fly. FLYING. [Cases 38 to 44, and table-case.] We have already seen that in the various groups of the parachuting animals a stage in the evolution of flight has been reached, i.e., support by an expansion of the body during long leaps. In the animals we have now to consider the adaptations for sustained flight are of the greatest specialis- ation, and the animals are able not only to move rapidly in the air but to support themselves for long periods of time and there perform the most varied evolutions. Flight has been acquired independently in four distinct groups of animals, viz., in the insects, pterodactyls, birds and bats.* It will be convenient to begin with the BIRDS, as it is in that group that the method of flight has been the most fully investigated. Structure of birds in relation to flight.—The general shape of a bird is such as to fit it for rapid locomotion. The pointed head, followed by the smooth rounded body, is adapted to cleave easily through the air. The bird’s organs are so arranged that the centre of gravity is on the lower portion of the body, as nearly as possible below the point of suspension by the wings, and the body is so delicately poised that outstretching of the neck or raising or lowering of the tail enables the bird at once to rise or sink in the air. The bones of the wing are homologous with the bones of the front limb of any other higher vertebrate, such as a lizard, dog or man ; in other words, a wing is nothing more than a highly modified front leg, the feathers with which it is clothed being in their turn the modified scales of the primitive reptilian ancestor of the bird. Firmness of the wing-bones being necessary, two of the original five digits have disappeared, and of the remaining three, two (the second and third) are more or less completely fused together, and the other (the first) is small. Flaps of skin extend between these fingers, * The number would, of course, be raised to six if the flying fishes Exoccrtus and Dactyloptcrus be regarded as truly flying animals.
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