File:Animal and vegetable physiology, considered with reference to natural theology (1836) (14784636733).jpg

Identifier: animalvegetable01roge (find matches)
Title: Animal and vegetable physiology, considered with reference to natural theology
Year: 1836 (1830s)
Authors: Roget, Peter Mark, 1779-1869
Subjects: Biology Physiology Plant physiology Natural theology
Publisher: Philadelphia, Carey, Lea & Blanchard
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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skin ofthe neck, which forms a kind of hood, capable of beingraised or depressed at the pleasure of the animal.^ Theseribs are entirely unconnected with the respiration of the ser-pent. In the Draco volans, which was to be furnished with rii- * Phil. Trans, for 1804, p. 346. FLYING LIZARD. 379 struments for assisting it in its distant leaps through the air,it is again the ribs which are resorted to for furnisliing thebasis of such an apparatus. On each side of the dorsal ver-tebrae, as is seen in the skeleton of this animal (Fig. 222,)the eight posterior ribs on each side, instead of having theusual curvature inwards, and instead of being continuedround to encircle the body, are extended outwards and elon-gated, and are covered with a thin cuticle, derived from thecommon integuments. The ordinary muscles which movethe ribs still remain, but with greatly increased power, andserve to flap these strangely formed wings at the pleasure ofthe animal, during its short aerial excursions. 222
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Among the mammalia, we meet with a few species whichhave a broad membrane, formed of a duplicature of the skin,extended like a cloak from the fore to the hind extremities,and enabling the animal to flutter in the air, and to break itsfall during its descent from the branches of trees. Struc-tures of this kind are possessed by the Sciurus volans^ or 380 THE MECHANICAL FUNCTIONS. flying squirrel, and also by some other species of the samegenus. They are seen on a still larger scale in the Lemurvolans, or Galeopitheciis. The resistance which these broadexpansions of skin oppose to the air, when the limbs arespread out, enables the animal to descend in perfect safetythrough that medium from very considerable heights: butthese appendages to the body are mere parachutes, not wings,and none of the animals which possess them can, by theirmeans, and with the utmost efforts which their muscles arecapable of exerting, ever rise from the ground, or even sus-pend themselves for a moment in the air

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