. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Mechano- and Equilibrium-Reception 521 don does not take place, and drowning results. The other circumstance is falling through air. A normal cat always lands on its feet regardless of its position at the instant of falling, by executing a series of righting re- actions while in the air. A bilaterally labyrinthectomized animal cannot right itself during a ^' ^'-^ Bilaterally labyrinthectomized pigeons-^" eventu- ally regain some ability to fly, only, however, when there is no interference with vision.
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Mechano- and Equilibrium-Reception 521 don does not take place, and drowning results. The other circumstance is falling through air. A normal cat always lands on its feet regardless of its position at the instant of falling, by executing a series of righting re- actions while in the air. A bilaterally labyrinthectomized animal cannot right itself during a ^' ^'-^ Bilaterally labyrinthectomized pigeons-^" eventu- ally regain some ability to fly, only, however, when there is no interference with vision. These observations seem to indicate that higher animals can, under most circumstances, compensate for the loss of both 0. Fig. 191. The ampulla and semicircular canal photographed in the living state (pike) before and during angular acceleration. B, oil droplet in canal before acceleration; C, oil droplet during acceleration; h, position of cupula before acceleration; c, position of cupula during acceleration. After Dohlman, from Fulton.™ The question naturally arises, "Where does the labyrinthectomized animal obtain the sensory information necessary for orientation?" The answer to this question has been supplied largely through the investigations of Magnus"'^ and has been excellently reviewed by Evans.^^ Labyrinthec- tomized dogs and cats orient their heads well when supported in air by the pelvis, f^owever, if these animals are blindfolded under similar circum- stances, no orientation of the head takes place. In rabbits and guinea pigs, renowned for their lack of visual righting reflexes, no orientation of the head takes place, even without blindfolding. These experiments indicate that vision is an important adjunct to labyrinthine function in orientation. If a labyrinthectomized rabbit is held in the air by the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - c
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