File:Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget (1834) (14776737484).jpg

Identifier: animalandvegetab01roge (find matches)
Title: Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget ..
Year: 1834 (1830s)
Authors: Roget, Peter Mark, 1779-1869
Subjects: Biology Physiology Plant physiology Natural theology
Publisher: London : W. Pickering
Contributing Library: University of California Libraries
Digitizing Sponsor: MSN

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in itsdistant leaps through the air, it is again the ribswhich are resorted to for furnishing the basis ofsuch an apparatus. On each side of the dorsalvertebrae, as is seen in the skeleton of this animal(Fig. 222), the eight posterior ribs on each side,instead of having the usual curvature inwards,and instead of being continued round to encirclethe body, are extended outwards and elongated,and are covered with a thin cuticle, derived fromthe common integuments. The ordinary muscleswhich move the ribs still remain, but withgreatly increased power, and serve to flap thesestrangely formed wings at the pleasure of theanimal, during its short aerial excursions. Among the mammalia we meet with a fewspecies, which have a broad membrane, formedof a duplicature of the skin, extended like acloak from the fore to the hind extremities, and * Phil. Trans, for 1804, p. 346. 550 THE MECHANICAL FUNCTIONS. enabling the animal to flutter in the air, andto break its fall during its descent from the 222
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branches of trees. Stmctures of this kind arepossessed by the Sciurus volcms, or flying squir-rel, and also by some other species of the samegenus. They are seen on a still larger scale in theLemur volcms, or Gnleopithecus. The resistancewhich these broad expansions of skin oppose tothe air, when the limbs are spread out, enablesthe animal to descend in perfect safety throughthat medium from very considerable heights:but these appendages to the body are mere para-chutes, not wings, and none of the animals which BAT. 551 possess them can, by their means, and with theutmost efforts which their muscles are capableof exerting, ever rise from the ground, or evensuspend themselves for a moment in the air. The only quadruped that can properly be saidto be endowed with the power of flying is theBat. In this animal the portions of the ske-leton (f, Fig. 223) which correspond to the pha- langes of the fingers are extended to an enor-mous length, and the pectoral muscles, whichmove the anterior

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