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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    leaps on his prey, and fastens his sharp and crooked claws in the flesh. Now, we must admire the mechanism by which they are preserved thus curved and sharp at their points. The last bone, that which supports the claw, is placed laterally to the next bone, and is so articulated with it that an elastic ligament (a) draws it back and to one side, and thus raises the sharp extre- mity of the claw upwards, and preserves it in that position. Whilst, there- fore, the claw is retracted as into a sheath between the toes, the nearer extremity of the furthest bone presses the ground, in the ordinary running of the animal. But when he makes his spring and strikes, the claws are uncased by the action of the flexor tendons; and in the Bengal tiger, they are so sharp and strong, and the stroke of his paw is so powerful, that they have been known to fracture a man's skull by a touch, in the act of leaping over him.* Apparatus of Lion's Claw. * The pads in the bottom of the lion's foot are soft cushions, which add to its elasticity, and must, in some degree, defend the animal in alighting from his bound. I could not comprehend how the powerful flexor muscles did not unsheath the claws whenever the lion made his spring, and only did so when he was excited to seize and hold the prey; to detect the cause, I made the dis- section from which the sketch has been taken. The last bone of the toe, from being drawn back by the elastic ligament (a) beyond the cen- tre of motion of the last joint, is placed in so peculiar a relation to the penultimate bone, that when the animal uses his foot in mere progres- sion, the flexor tendon (b), although inserted into it, only acts in forcing the nearer end, and the cushion of the toe, to the ground. But when the lion strikes his prey to seize it, a more general excitement takes place in the muscles called interossei and extensors (d, e) ; the relative position of the two List bones is altered; the nearer end of the last bone is withdrawn from beyond the centre of motion of the joint, so that the action of the flexor tendon can now draw it forward or in a line with the penultimate bone, — and then the claw can be unsheathed, and prepared to hold or to tear.