. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Mechano- and Equilibrium-Reception 517 cochlea, functions in hearing; (2) the upper portion, consisting of the utriculus and the semicircular canals, functions in orientation. The utric- ulus conforms reasonably closely to the basic plan of a statocyst, (page 514). The semicircular canals are bent tubes, both ends of which com- municate with the utriculus. The bent tubes bear an enlargement at one end, the ampulla, in which is located the sense organ (Fig. 186), consisting of the crista and the gelatinous cupula
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Mechano- and Equilibrium-Reception 517 cochlea, functions in hearing; (2) the upper portion, consisting of the utriculus and the semicircular canals, functions in orientation. The utric- ulus conforms reasonably closely to the basic plan of a statocyst, (page 514). The semicircular canals are bent tubes, both ends of which com- municate with the utriculus. The bent tubes bear an enlargement at one end, the ampulla, in which is located the sense organ (Fig. 186), consisting of the crista and the gelatinous cupula, which approximately fills the cavity of the ampulla (p. 475, Ch. 13). Fibers in the vestibular branch of the eighth nerve are of three types: those activated onlv bv mechanical vibration of low frequency; those acti- vated by tilting movements only; and those activated by angular accelera tion.^- McNally and Tait'^^ rendered the utriculus of frogs non-functional by cautery without encroaching on the semicircular canals and determined that the response to tilting and linear acceleration was abolished. It is gen-. Fig. 186. Diagrammatic sketch of the cupula and crista after Kolmer. A, hair cells whose terminal processes protrude into F, the gelatinous cupula; B, support- ing cells; D, large nerve fibers; E, small nerve fibers. From ;'" erally accepted that the utriculus responds to these movements. The function of the sacculus is less clearly established. In the frog, section of the ner\'es from the saccular maculae does not produce any disturbance of orientation.'' Von Buddenbrock^^ states that the sacculus does not function in orientation except in rabbits, in which vertical eye movements are elicited by stimulation of the sacculus. The consensus at present""' -^^ is that the sacculus responds to mechanical vibrations of low frequency. Con- cerning the function of the semicircular canals, there exists a vast litera j-yjg 40. 14, 70 j]^p work of Lowe
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