The hand : its mechanism and vital endowments, as evincing design / by Charles Bell.

  • Bell, Charles, Sir, 1774-1842.
Date:
1860
Catalogue details

Licence: Public Domain Mark

Credit: The hand : its mechanism and vital endowments, as evincing design / by Charles Bell. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    We thus see how Nature completes her work when the ani- mal is destined to rise buoyant and powerful in the air :—the whole texture of the frame is altered, and made light in a man- ner consistent with strength; the mechanism of the anterior extremity is changed, and the muscles of the trunk are differ- ently directed. But we are tempted to examine other instances, where the means, we would almost say, are more awkwardly suited for their purpose; that is, where the system of bones and muscles peculiar to the quadruped being preserved, the ani- mal has still the power of launching into the air. We have already noticed how the structure of the bat is adapted to flight; but there are other animals, differing from birds more widely than it, which enjoy the function, though in a lesser degree. For example, the flying squirrel {Pieromys volucella), being chased to the end of a bough, spreads out the mantle which reaches along both its sides from the anterior to the posterior extremity, and drops in the air; and during its descent, it is met by such a resistance of the air from its extended skin and bushy tail, that it can direct its flight obliquely, and even turn, without any adaptation of the anterior extremity. Among reptiles, a provision of the same kind exists in the Draco fimbriatus ; which, after creeping to a height, can drop safely to the ground, under the protection of a sort of para- chute, formed by its extended skin. This is no inapt illustra- tion : it is not the bones of the fingers that are here used to extend the web; but the ribs, which are unnecessary, in this animal, for breathing, are prolonged in a remarkable manner, like the whalebones of an umbrella, and upon them the skin is expanded. This brings us to a very curious subject,—the condition of some of those Saurian reptiles, the remains of which are found only in a fossil state, most abundantly in the lias and oolite, termed the ancient strata of the Jura. The Pterodactyle of Cuvier is an animal which seems to confound all our notions of system. A lizard, yet its mouth was like the long bill of a bird, and its flexible neck corresponded; but it had teeth in its jaws like those of a crocodile. The bones of the anterior extremity were elongated, and fashioned somewhat like those in the wing a contrary direction, and that the | the wind may have arisen from that idea of migrating birds flying against [ mistake.